lager/test/lager_test_backend.erl

%% -------------------------------------------------------------------
%%
%% Copyright (c) 2011-2015 Basho Technologies, Inc.
%%
%% This file is provided to you under the Apache License,
%% Version 2.0 (the "License"); you may not use this file
%% except in compliance with the License.  You may obtain
%% a copy of the License at
%%
%%   http://www.apache.org/licenses/LICENSE-2.0
%%
%% Unless required by applicable law or agreed to in writing,
%% software distributed under the License is distributed on an
%% "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
%% KIND, either express or implied.  See the License for the
%% specific language governing permissions and limitations
%% under the License.
%%
%% -------------------------------------------------------------------

-module(lager_test_backend).

-include("lager.hrl").

-behaviour(gen_event).

-export([init/1, handle_call/2, handle_event/2, handle_info/2, terminate/2,
        code_change/3]).

-define(TEST_SINK_NAME, '__lager_test_sink').              %% <-- used by parse transform
-define(TEST_SINK_EVENT, '__lager_test_sink_lager_event'). %% <-- used by lager API calls and internals for gen_event

-record(state, {level :: list(), buffer :: list(), ignored :: term()}).
-compile({parse_transform, lager_transform}).

-ifdef(TEST).
-include_lib("eunit/include/eunit.hrl").
-record(test, {attrs :: list(), format :: list(), args :: list()}).
-export([pop/0, count/0, count_ignored/0, flush/0, print_state/0]).
-endif.

init(Level) ->
    {ok, #state{level=lager_util:config_to_mask(Level), buffer=[], ignored=[]}}.

handle_call(count, #state{buffer=Buffer} = State) ->
    {ok, length(Buffer), State};
handle_call(count_ignored, #state{ignored=Ignored} = State) ->
    {ok, length(Ignored), State};
handle_call(flush, State) ->
    {ok, ok, State#state{buffer=[], ignored=[]}};
handle_call(pop, #state{buffer=Buffer} = State) ->
    case Buffer of
        [] ->
            {ok, undefined, State};
        [H|T] ->
            {ok, H, State#state{buffer=T}}
    end;
handle_call(get_loglevel, #state{level=Level} = State) ->
    {ok, Level, State};
handle_call({set_loglevel, Level}, State) ->
    {ok, ok, State#state{level=lager_util:config_to_mask(Level)}};
handle_call(print_state, State) ->
    spawn(fun() -> lager:info("State ~p", [lager:pr(State, ?MODULE)]) end),
    timer:sleep(100),
    {ok, ok, State};
handle_call(print_bad_state, State) ->
    spawn(fun() -> lager:info("State ~p", [lager:pr({state, 1}, ?MODULE)]) end),
    timer:sleep(100),
    {ok, ok, State};
handle_call(_Request, State) ->
    {ok, ok, State}.

handle_event({log, Msg},
             #state{level=LogLevel,buffer=Buffer,ignored=Ignored} = State) ->
    case lager_util:is_loggable(Msg, LogLevel, ?MODULE) of
        true ->
            {ok, State#state{buffer=Buffer ++
                             [{lager_msg:severity_as_int(Msg),
                               lager_msg:datetime(Msg),
                               lager_msg:message(Msg), lager_msg:metadata(Msg)}]}};
        _ ->
            {ok, State#state{ignored=Ignored ++ [ignored]}}
    end;
handle_event(_Event, State) ->
    {ok, State}.

handle_info(_Info, State) ->
    {ok, State}.

terminate(_Reason, _State) ->
    ok.

code_change(_OldVsn, State, _Extra) ->
    {ok, State}.

-ifdef(TEST).

pop() ->
    pop(lager_event).

count() ->
    count(lager_event).

count_ignored() ->
    count_ignored(lager_event).

flush() ->
    flush(lager_event).

print_state() ->
    print_state(lager_event).

print_bad_state() ->
    print_bad_state(lager_event).

pop(Sink) ->
    gen_event:call(Sink, ?MODULE, pop).

count(Sink) ->
    gen_event:call(Sink, ?MODULE, count).

count_ignored(Sink) ->
    gen_event:call(Sink, ?MODULE, count_ignored).

flush(Sink) ->
    gen_event:call(Sink, ?MODULE, flush).

print_state(Sink) ->
    gen_event:call(Sink, ?MODULE, print_state).

print_bad_state(Sink) ->
    gen_event:call(Sink, ?MODULE, print_bad_state).


has_line_numbers() ->
    %% are we R15 or greater
    % this gets called a LOT - cache the answer
    case erlang:get({?MODULE, has_line_numbers}) of
        undefined ->
            R = otp_version() >= 15,
            erlang:put({?MODULE, has_line_numbers}, R),
            R;
        Bool ->
            Bool
    end.

otp_version() ->
    otp_version(erlang:system_info(otp_release)).

otp_version([$R | Rel]) ->
    {Ver, _} = string:to_integer(Rel),
    Ver;
otp_version(Rel) ->
    {Ver, _} = string:to_integer(Rel),
    Ver.

not_running_test() ->
    ?assertEqual({error, lager_not_running}, lager:log(info, self(), "not running")).

lager_test_() ->
    {foreach,
        fun setup/0,
        fun cleanup/1,
        [
            {"observe that there is nothing up my sleeve",
                fun() ->
                        ?assertEqual(undefined, pop()),
                        ?assertEqual(0, count())
                end
            },
            {"test sink not running",
                fun() ->
                         ?assertEqual({error, {sink_not_configured, test}}, lager:log(test, info, self(), "~p", "not running"))
                end
            },
            {"logging works",
                fun() ->
                        lager:warning("test message"),
                        ?assertEqual(1, count()),
                        {Level, _Time, Message, _Metadata}  = pop(),
                        ?assertMatch(Level, lager_util:level_to_num(warning)),
                        ?assertEqual("test message", Message),
                        ok
                end
            },
            {"unsafe logging works",
                fun() ->
                        lager:warning_unsafe("test message"),
                        ?assertEqual(1, count()),
                        {Level, _Time, Message, _Metadata}  = pop(),
                        ?assertMatch(Level, lager_util:level_to_num(warning)),
                        ?assertEqual("test message", Message),
                        ok
                end
            },
            {"logging with arguments works",
                fun() ->
                        lager:warning("test message ~p", [self()]),
                        ?assertEqual(1, count()),
                        {Level, _Time, Message,_Metadata}  = pop(),
                        ?assertMatch(Level, lager_util:level_to_num(warning)),
                        ?assertEqual(lists:flatten(io_lib:format("test message ~p", [self()])), lists:flatten(Message)),
                        ok
                end
            },
            {"unsafe logging with args works",
                fun() ->
                        lager:warning("test message ~p", [self()]),
                        ?assertEqual(1, count()),
                        {Level, _Time, Message,_Metadata}  = pop(),
                        ?assertMatch(Level, lager_util:level_to_num(warning)),
                        ?assertEqual(lists:flatten(io_lib:format("test message ~p", [self()])), lists:flatten(Message)),
                        ok
                end
            },
            {"logging works from inside a begin/end block",
                fun() ->
                        ?assertEqual(0, count()),
                        begin
                                lager:warning("test message 2")
                        end,
                        ?assertEqual(1, count()),
                        ok
                end
            },
            {"logging works from inside a list comprehension",
                fun() ->
                        ?assertEqual(0, count()),
                        [lager:warning("test message") || _N <- lists:seq(1, 10)],
                        ?assertEqual(10, count()),
                        ok
                end
            },
            {"logging works from a begin/end block inside a list comprehension",
                fun() ->
                        ?assertEqual(0, count()),
                        [ begin lager:warning("test message") end || _N <- lists:seq(1, 10)],
                        ?assertEqual(10, count()),
                        ok
                end
            },
            {"logging works from a nested list comprehension",
                fun() ->
                        ?assertEqual(0, count()),
                        [ [lager:warning("test message") || _N <- lists:seq(1, 10)] ||
                            _I <- lists:seq(1, 10)],
                        ?assertEqual(100, count()),
                        ok
                end
            },
            {"variables inplace of literals in logging statements work",
                fun() ->
                        ?assertEqual(0, count()),
                        Attr = [{a, alpha}, {b, beta}],
                        Fmt = "format ~p",
                        Args = [world],
                        lager:info(Attr, "hello"),
                        lager:info(Attr, "hello ~p", [world]),
                        lager:info(Fmt, [world]),
                        lager:info("hello ~p", Args),
                        lager:info(Attr, "hello ~p", Args),
                        lager:info([{d, delta}, {g, gamma}], Fmt, Args),
                        ?assertEqual(6, count()),
                        {_Level, _Time, Message, Metadata}  = pop(),
                        ?assertMatch([{a, alpha}, {b, beta}|_], Metadata),
                        ?assertEqual("hello", lists:flatten(Message)),
                        {_Level, _Time2, Message2, _Metadata2}  = pop(),
                        ?assertEqual("hello world", lists:flatten(Message2)),
                        {_Level, _Time3, Message3, _Metadata3}  = pop(),
                        ?assertEqual("format world", lists:flatten(Message3)),
                        {_Level, _Time4, Message4, _Metadata4}  = pop(),
                        ?assertEqual("hello world", lists:flatten(Message4)),
                        {_Level, _Time5, Message5, _Metadata5}  = pop(),
                        ?assertEqual("hello world", lists:flatten(Message5)),
                        {_Level, _Time6, Message6, Metadata6}  = pop(),
                        ?assertMatch([{d, delta}, {g, gamma}|_], Metadata6),
                        ?assertEqual("format world", lists:flatten(Message6)),
                        ok
                end
            },
            {"list comprehension inplace of literals in logging statements work",
                fun() ->
                        ?assertEqual(0, count()),
                        Attr = [{a, alpha}, {b, beta}],
                        Fmt = "format ~p",
                        Args = [world],
                        lager:info([{K, atom_to_list(V)} || {K, V} <- Attr], "hello"),
                        lager:info([{K, atom_to_list(V)} || {K, V} <- Attr], "hello ~p", [{atom, X} || X <- Args]),
                        lager:info([X || X <- Fmt], [world]),
                        lager:info("hello ~p", [{atom, X} || X <- Args]),
                        lager:info([{K, atom_to_list(V)} || {K, V} <- Attr], "hello ~p", [{atom, X} || X <- Args]),
                        lager:info([{d, delta}, {g, gamma}], Fmt, [{atom, X} || X <- Args]),
                        ?assertEqual(6, count()),
                        {_Level, _Time, Message, Metadata}  = pop(),
                        ?assertMatch([{a, "alpha"}, {b, "beta"}|_], Metadata),
                        ?assertEqual("hello", lists:flatten(Message)),
                        {_Level, _Time2, Message2, _Metadata2}  = pop(),
                        ?assertEqual("hello {atom,world}", lists:flatten(Message2)),
                        {_Level, _Time3, Message3, _Metadata3}  = pop(),
                        ?assertEqual("format world", lists:flatten(Message3)),
                        {_Level, _Time4, Message4, _Metadata4}  = pop(),
                        ?assertEqual("hello {atom,world}", lists:flatten(Message4)),
                        {_Level, _Time5, Message5, _Metadata5}  = pop(),
                        ?assertEqual("hello {atom,world}", lists:flatten(Message5)),
                        {_Level, _Time6, Message6, Metadata6}  = pop(),
                        ?assertMatch([{d, delta}, {g, gamma}|_], Metadata6),
                        ?assertEqual("format {atom,world}", lists:flatten(Message6)),
                        ok
                end
            },
            {"function calls inplace of literals in logging statements work",
                fun() ->
                        ?assertEqual(0, count()),
                        put(attrs, [{a, alpha}, {b, beta}]),
                        put(format, "format ~p"),
                        put(args, [world]),
                        lager:info(get(attrs), "hello"),
                        lager:info(get(attrs), "hello ~p", get(args)),
                        lager:info(get(format), [world]),
                        lager:info("hello ~p", erlang:get(args)),
                        lager:info(fun() -> get(attrs) end(), "hello ~p", get(args)),
                        lager:info([{d, delta}, {g, gamma}], get(format), get(args)),
                        ?assertEqual(6, count()),
                        {_Level, _Time, Message, Metadata}  = pop(),
                        ?assertMatch([{a, alpha}, {b, beta}|_], Metadata),
                        ?assertEqual("hello", lists:flatten(Message)),
                        {_Level, _Time2, Message2, _Metadata2}  = pop(),
                        ?assertEqual("hello world", lists:flatten(Message2)),
                        {_Level, _Time3, Message3, _Metadata3}  = pop(),
                        ?assertEqual("format world", lists:flatten(Message3)),
                        {_Level, _Time4, Message4, _Metadata4}  = pop(),
                        ?assertEqual("hello world", lists:flatten(Message4)),
                        {_Level, _Time5, Message5, _Metadata5}  = pop(),
                        ?assertEqual("hello world", lists:flatten(Message5)),
                        {_Level, _Time6, Message6, Metadata6}  = pop(),
                        ?assertMatch([{d, delta}, {g, gamma}|_], Metadata6),
                        ?assertEqual("format world", lists:flatten(Message6)),
                        ok
                end
            },
            {"record fields inplace of literals in logging statements work",
                fun() ->
                        ?assertEqual(0, count()),
                        Test = #test{attrs=[{a, alpha}, {b, beta}], format="format ~p", args=[world]},
                        lager:info(Test#test.attrs, "hello"),
                        lager:info(Test#test.attrs, "hello ~p", Test#test.args),
                        lager:info(Test#test.format, [world]),
                        lager:info("hello ~p", Test#test.args),
                        lager:info(Test#test.attrs, "hello ~p", Test#test.args),
                        lager:info([{d, delta}, {g, gamma}], Test#test.format, Test#test.args),
                        ?assertEqual(6, count()),
                        {_Level, _Time, Message, Metadata}  = pop(),
                        ?assertMatch([{a, alpha}, {b, beta}|_], Metadata),
                        ?assertEqual("hello", lists:flatten(Message)),
                        {_Level, _Time2, Message2, _Metadata2}  = pop(),
                        ?assertEqual("hello world", lists:flatten(Message2)),
                        {_Level, _Time3, Message3, _Metadata3}  = pop(),
                        ?assertEqual("format world", lists:flatten(Message3)),
                        {_Level, _Time4, Message4, _Metadata4}  = pop(),
                        ?assertEqual("hello world", lists:flatten(Message4)),
                        {_Level, _Time5, Message5, _Metadata5}  = pop(),
                        ?assertEqual("hello world", lists:flatten(Message5)),
                        {_Level, _Time6, Message6, Metadata6}  = pop(),
                        ?assertMatch([{d, delta}, {g, gamma}|_], Metadata6),
                        ?assertEqual("format world", lists:flatten(Message6)),
                        ok
                end
            },

            {"log messages below the threshold are ignored",
                fun() ->
                        ?assertEqual(0, count()),
                        lager:debug("this message will be ignored"),
                        ?assertEqual(0, count()),
                        ?assertEqual(0, count_ignored()),
                        lager_config:set(loglevel, {element(2, lager_util:config_to_mask(debug)), []}),
                        lager:debug("this message should be ignored"),
                        ?assertEqual(0, count()),
                        ?assertEqual(1, count_ignored()),
                        lager:set_loglevel(?MODULE, debug),
                        ?assertEqual({?DEBUG bor ?INFO bor ?NOTICE bor ?WARNING bor ?ERROR bor ?CRITICAL bor ?ALERT bor ?EMERGENCY, []}, lager_config:get(loglevel)),
                        lager:debug("this message should be logged"),
                        ?assertEqual(1, count()),
                        ?assertEqual(1, count_ignored()),
                        ?assertEqual(debug, lager:get_loglevel(?MODULE)),
                        ok
                end
            },
            {"tracing works",
                fun() ->
                        lager_config:set(loglevel, {element(2, lager_util:config_to_mask(error)), []}),
                        ok = lager:info("hello world"),
                        ?assertEqual(0, count()),
                        lager:trace(?MODULE, [{module, ?MODULE}], debug),
                        ?assertMatch({?ERROR bor ?CRITICAL bor ?ALERT bor ?EMERGENCY, _}, lager_config:get(loglevel)),
                        %% elegible for tracing
                        ok = lager:info("hello world"),
                        %% NOT elegible for tracing
                        ok = lager:log(info, [{pid, self()}], "hello world"),
                        ?assertEqual(1, count()),
                        ok
                end
            },
            {"tracing works with custom attributes",
                fun() ->
                        lager:set_loglevel(?MODULE, error),
                        ?assertEqual({?ERROR bor ?CRITICAL bor ?ALERT bor ?EMERGENCY, []}, lager_config:get(loglevel)),
                        lager_config:set(loglevel, {element(2, lager_util:config_to_mask(error)), []}),
                        lager:info([{requestid, 6}], "hello world"),
                        ?assertEqual(0, count()),
                        lager:trace(?MODULE, [{requestid, 6}, {foo, bar}], debug),
                        lager:info([{requestid, 6}, {foo, bar}], "hello world"),
                        ?assertEqual(1, count()),
                        lager:trace(?MODULE, [{requestid, '*'}], debug),
                        lager:info([{requestid, 6}], "hello world"),
                        ?assertEqual(2, count()),
                        lager:clear_all_traces(),
                        lager:info([{requestid, 6}], "hello world"),
                        ?assertEqual(2, count()),
                        ok
                end
            },
            {"tracing works with custom attributes and event stream processing",
                fun() ->
                        lager:set_loglevel(?MODULE, error),
                        ?assertEqual({?ERROR bor ?CRITICAL bor ?ALERT bor ?EMERGENCY, []}, lager_config:get(loglevel)),
                        lager_config:set(loglevel, {element(2, lager_util:config_to_mask(error)), []}),
                        lager:info([{requestid, 6}], "hello world"),
                        ?assertEqual(0, count()),
                        lager:trace(?MODULE, [{requestid, '>', 5}, {requestid, '<', 7}, {foo, bar}], debug),
                        lager:info([{requestid, 5}, {foo, bar}], "hello world"),
                        lager:info([{requestid, 6}, {foo, bar}], "hello world"),
                        ?assertEqual(1, count()),
                        lager:clear_all_traces(),
                        lager:trace(?MODULE, [{requestid, '>', 8}, {foo, bar}]),
                        lager:info([{foo, bar}], "hello world"),
                        lager:info([{requestid, 6}], "hello world"),
                        lager:info([{requestid, 7}], "hello world"),
                        lager:info([{requestid, 8}], "hello world"),
                        lager:info([{requestid, 9}, {foo, bar}], "hello world"),
                        lager:info([{requestid, 10}], "hello world"),
                        ?assertEqual(2, count()),
                        lager:trace(?MODULE, [{requestid, '>', 8}]),
                        lager:info([{foo, bar}], "hello world"),
                        lager:info([{requestid, 6}], "hello world"),
                        lager:info([{requestid, 7}], "hello world"),
                        lager:info([{requestid, 8}], "hello world"),
                        lager:info([{requestid, 9}, {foo, bar}], "hello world"),
                        lager:info([{requestid, 10}], "hello world"),
                        ?assertEqual(4, count()),
                        lager:trace(?MODULE, [{foo, '=', bar}]),
                        lager:info([{foo, bar}], "hello world"),
                        lager:info([{requestid, 6}], "hello world"),
                        lager:info([{requestid, 7}], "hello world"),
                        lager:info([{requestid, 8}], "hello world"),
                        lager:info([{requestid, 9}, {foo, bar}], "hello world"),
                        lager:info([{requestid, 10}], "hello world"),
                        lager:trace(?MODULE, [{fu, '!'}]),
                        lager:info([{foo, bar}], "hello world"),
                        lager:info([{ooh, car}], "hello world"),
                        lager:info([{fu, bar}], "hello world"),
                        lager:trace(?MODULE, [{fu, '*'}]),
                        lager:info([{fu, bar}], "hello world"),
                        ?assertEqual(10, count()),
                        lager:clear_all_traces(),
                        lager:info([{requestid, 6}], "hello world"),
                        ?assertEqual(10, count()),
                        ok
                end
            },
            {"tracing custom attributes works with event stream processing statistics and reductions",
                fun() ->
                        lager:set_loglevel(?MODULE, error),
                        ?assertEqual({?ERROR bor ?CRITICAL bor ?ALERT bor ?EMERGENCY, []}, lager_config:get(loglevel)),
                        lager_config:set(loglevel, {element(2, lager_util:config_to_mask(error)), []}),
                        lager:info([{requestid, 6}], "hello world"),
                        ?assertEqual(0, count()),
                        lager:trace(?MODULE, [{beta, '*'}]),
                        lager:trace(?MODULE, [{meta, "data"}]),
                        lager:info([{meta, "data"}], "hello world"),
                        lager:info([{beta, 2}], "hello world"),
                        lager:info([{beta, 2.1}, {foo, bar}], "hello world"),
                        lager:info([{meta, <<"data">>}], "hello world"),
                        ?assertEqual(8, ?DEFAULT_TRACER:info(input)),
                        ?assertEqual(6, ?DEFAULT_TRACER:info(output)),
                        ?assertEqual(2, ?DEFAULT_TRACER:info(filter)),
                        lager:clear_all_traces(),
                        lager:trace(?MODULE, [{meta, "data"}]),
                        lager:trace(?MODULE, [{beta, '>', 2}, {beta, '<', 2.12}]),
                        lager:info([{meta, "data"}], "hello world"),
                        lager:info([{beta, 2}], "hello world"),
                        lager:info([{beta, 2.1}, {foo, bar}], "hello world"),
                        lager:info([{meta, <<"data">>}], "hello world"),
                        ?assertEqual(8, ?DEFAULT_TRACER:info(input)),
                        ?assertEqual(4, ?DEFAULT_TRACER:info(output)),
                        ?assertEqual(4, ?DEFAULT_TRACER:info(filter)),
                        lager:clear_all_traces(),
                        lager:trace_console([{beta, '>', 2}, {meta, "data"}]),
                        lager:trace_console([{beta, '>', 2}, {beta, '<', 2.12}]),
                        Reduced = {all,[{any,[{beta,'<',2.12},{meta,'=',"data"}]},
                                              {beta,'>',2}]},
                        ?assertEqual(Reduced, ?DEFAULT_TRACER:info('query')),

                        lager:clear_all_traces(),
                        lager:info([{requestid, 6}], "hello world"),
                        ?assertEqual(5, count()),
                        ok
                end
            },
            {"persistent traces work",
                fun() ->
                        ?assertEqual(0, count()),
                        lager:debug([{foo, bar}], "hello world"),
                        ?assertEqual(0, count()),
                        application:stop(lager),
                        application:set_env(lager, traces, [{lager_test_backend, [{foo, bar}], debug}]),
                        lager:start(),
                        lager:debug([{foo, bar}], "hello world"),
                        ?assertEqual(1, count()),
                        application:unset_env(lager, traces),
                        ok
                end
            },
            {"tracing honors loglevel",
                fun() ->
                        lager:set_loglevel(?MODULE, error),
                        ?assertEqual({?ERROR bor ?CRITICAL bor ?ALERT bor ?EMERGENCY, []}, lager_config:get(loglevel)),
                        {ok, T} = lager:trace(?MODULE, [{module, ?MODULE}], notice),
                        ok = lager:info("hello world"),
                        ?assertEqual(0, count()),
                        ok = lager:notice("hello world"),
                        ?assertEqual(1, count()),
                        lager:stop_trace(T),
                        ok = lager:notice("hello world"),
                        ?assertEqual(1, count()),
                        ok
                end
            },
            {"stopped trace stops and removes its event handler - default sink (gh#267)",
                fun() ->
                        Sink = ?DEFAULT_SINK,
                        StartHandlers = gen_event:which_handlers(Sink),
                        {_, T0} = lager_config:get({Sink, loglevel}),
                        StartGlobal = lager_config:global_get(handlers),
                        ?assertEqual([], T0),
                        {ok, TestTrace1} = lager:trace_file("/tmp/test", [{a,b}]),
                        MidHandlers = gen_event:which_handlers(Sink),
                        {ok, TestTrace2} = lager:trace_file("/tmp/test", [{c,d}]),
                        MidHandlers = gen_event:which_handlers(Sink),
                        ?assertEqual(length(StartHandlers)+1, length(MidHandlers)),
                        MidGlobal = lager_config:global_get(handlers),
                        ?assertEqual(length(StartGlobal)+1, length(MidGlobal)),
                        {_, T1} = lager_config:get({Sink, loglevel}),
                        ?assertEqual(2, length(T1)),
                        ok = lager:stop_trace(TestTrace1),
                        {_, T2} = lager_config:get({Sink, loglevel}),
                        ?assertEqual(1, length(T2)),
                        ?assertEqual(length(StartHandlers)+1, length(
                                                                gen_event:which_handlers(Sink))),

                        ?assertEqual(length(StartGlobal)+1, length(lager_config:global_get(handlers))),
                        ok = lager:stop_trace(TestTrace2),
                        EndHandlers = gen_event:which_handlers(?DEFAULT_SINK),
                        EndGlobal = lager_config:global_get(handlers),
                        {_, T3} = lager_config:get({Sink, loglevel}),
                        ?assertEqual([], T3),
                        ?assertEqual(StartHandlers, EndHandlers),
                        ?assertEqual(StartGlobal, EndGlobal),
                        ok
                end
            },
            {"record printing works",
                fun() ->
                        print_state(),
                        {Level, _Time, Message, _Metadata}  = pop(),
                        ?assertMatch(Level, lager_util:level_to_num(info)),
                        {mask, Mask} = lager_util:config_to_mask(info),
                        ?assertEqual("State #state{level={mask,"++integer_to_list(Mask)++"},buffer=[],ignored=[]}", lists:flatten(Message)),
                        ok
                end
            },
            {"record printing fails gracefully",
                fun() ->
                        print_bad_state(),
                        {Level, _Time, Message, _Metadata}  = pop(),
                        ?assertMatch(Level, lager_util:level_to_num(info)),
                        ?assertEqual("State {state,1}", lists:flatten(Message)),
                        ok
                end
            },
            {"record printing fails gracefully when no lager_record attribute",
                fun() ->
                        spawn(fun() -> lager:info("State ~p", [lager:pr({state, 1}, lager)]) end),
                        timer:sleep(100),
                        {Level, _Time, Message, _Metadata}  = pop(),
                        ?assertMatch(Level, lager_util:level_to_num(info)),
                        ?assertEqual("State {state,1}", lists:flatten(Message)),
                        ok
                end
            },
            {"record printing fails gracefully when input is not a tuple",
                fun() ->
                        spawn(fun() -> lager:info("State ~p", [lager:pr(ok, lager)]) end),
                        timer:sleep(100),
                        {Level, _Time, Message, _Metadata}  = pop(),
                        ?assertMatch(Level, lager_util:level_to_num(info)),
                        ?assertEqual("State ok", lists:flatten(Message)),
                        ok
                end
            },
            {"record printing fails gracefully when module is invalid",
                fun() ->
                        spawn(fun() -> lager:info("State ~p", [lager:pr({state, 1}, not_a_module)]) end),
                        timer:sleep(1000),
                        {Level, _Time, Message, _Metadata}  = pop(),
                        ?assertMatch(Level, lager_util:level_to_num(info)),
                        ?assertEqual("State {state,1}", lists:flatten(Message)),
                        ok
                end
            },
            {"installing a new handler adjusts the global loglevel if necessary",
                fun() ->
                        ?assertEqual({?INFO bor ?NOTICE bor ?WARNING bor ?ERROR bor ?CRITICAL bor ?ALERT bor ?EMERGENCY, []}, lager_config:get(loglevel)),
                        supervisor:start_child(lager_handler_watcher_sup, [lager_event, {?MODULE, foo}, debug]),
                        ?assertEqual({?DEBUG bor ?INFO bor ?NOTICE bor ?WARNING bor ?ERROR bor ?CRITICAL bor ?ALERT bor ?EMERGENCY, []}, lager_config:get(loglevel)),
                        ok
                end
            },
            {"metadata in the process dictionary works",
                fun() ->
                        lager:md([{platypus, gravid}, {sloth, hirsute}, {duck, erroneous}]),
                        lager:info("I sing the animal kingdom electric!"),
                        {_Level, _Time, _Message, Metadata}  = pop(),
                        ?assertEqual(gravid, proplists:get_value(platypus, Metadata)),
                        ?assertEqual(hirsute, proplists:get_value(sloth, Metadata)),
                        ?assertEqual(erroneous, proplists:get_value(duck, Metadata)),
                        ?assertEqual(undefined, proplists:get_value(eagle, Metadata)),
                        lager:md([{platypus, gravid}, {sloth, hirsute}, {eagle, superincumbent}]),
                        lager:info("I sing the animal kingdom dielectric!"),
                        {_Level2, _Time2, _Message2, Metadata2}  = pop(),
                        ?assertEqual(gravid, proplists:get_value(platypus, Metadata2)),
                        ?assertEqual(hirsute, proplists:get_value(sloth, Metadata2)),
                        ?assertEqual(undefined, proplists:get_value(duck, Metadata2)),
                        ?assertEqual(superincumbent, proplists:get_value(eagle, Metadata2)),
                        ok
                end
            },
            {"unsafe messages really are not truncated",
                fun() ->
                        lager:info_unsafe("doom, doom has come upon you all ~p", [string:copies("doom", 1500)]),
                        {_, _, Msg,_Metadata} = pop(),
                        ?assert(length(lists:flatten(Msg)) == 6035)
                end
            },
            {"can't store invalid metadata",
                fun() ->
                        ?assertEqual(ok, lager:md([{platypus, gravid}, {sloth, hirsute}, {duck, erroneous}])),
                        ?assertError(badarg, lager:md({flamboyant, flamingo})),
                        ?assertError(badarg, lager:md("zookeeper zephyr")),
                        ok
                end
            }
        ]
    }.

extra_sinks_test_() ->
    {foreach,
        fun setup_sink/0,
        fun cleanup/1,
        [
            {"observe that there is nothing up my sleeve",
                fun() ->
                        ?assertEqual(undefined, pop(?TEST_SINK_EVENT)),
                        ?assertEqual(0, count(?TEST_SINK_EVENT))
                end
            },
            {"logging works",
                fun() ->
                        ?TEST_SINK_NAME:warning("test message"),
                        ?assertEqual(1, count(?TEST_SINK_EVENT)),
                        {Level, _Time, Message, _Metadata}  = pop(?TEST_SINK_EVENT),
                        ?assertMatch(Level, lager_util:level_to_num(warning)),
                        ?assertEqual("test message", Message),
                        ok
                end
            },
            {"logging with arguments works",
                fun() ->
                        ?TEST_SINK_NAME:warning("test message ~p", [self()]),
                        ?assertEqual(1, count(?TEST_SINK_EVENT)),
                        {Level, _Time, Message,_Metadata}  = pop(?TEST_SINK_EVENT),
                        ?assertMatch(Level, lager_util:level_to_num(warning)),
                        ?assertEqual(lists:flatten(io_lib:format("test message ~p", [self()])), lists:flatten(Message)),
                        ok
                end
            },
            {"variables inplace of literals in logging statements work",
                fun() ->
                        ?assertEqual(0, count(?TEST_SINK_EVENT)),
                        Attr = [{a, alpha}, {b, beta}],
                        Fmt = "format ~p",
                        Args = [world],
                        ?TEST_SINK_NAME:info(Attr, "hello"),
                        ?TEST_SINK_NAME:info(Attr, "hello ~p", [world]),
                        ?TEST_SINK_NAME:info(Fmt, [world]),
                        ?TEST_SINK_NAME:info("hello ~p", Args),
                        ?TEST_SINK_NAME:info(Attr, "hello ~p", Args),
                        ?TEST_SINK_NAME:info([{d, delta}, {g, gamma}], Fmt, Args),
                        ?assertEqual(6, count(?TEST_SINK_EVENT)),
                        {_Level, _Time, Message, Metadata}  = pop(?TEST_SINK_EVENT),
                        ?assertMatch([{a, alpha}, {b, beta}|_], Metadata),
                        ?assertEqual("hello", lists:flatten(Message)),
                        {_Level, _Time2, Message2, _Metadata2}  = pop(?TEST_SINK_EVENT),
                        ?assertEqual("hello world", lists:flatten(Message2)),
                        {_Level, _Time3, Message3, _Metadata3}  = pop(?TEST_SINK_EVENT),
                        ?assertEqual("format world", lists:flatten(Message3)),
                        {_Level, _Time4, Message4, _Metadata4}  = pop(?TEST_SINK_EVENT),
                        ?assertEqual("hello world", lists:flatten(Message4)),
                        {_Level, _Time5, Message5, _Metadata5}  = pop(?TEST_SINK_EVENT),
                        ?assertEqual("hello world", lists:flatten(Message5)),
                        {_Level, _Time6, Message6, Metadata6}  = pop(?TEST_SINK_EVENT),
                        ?assertMatch([{d, delta}, {g, gamma}|_], Metadata6),
                        ?assertEqual("format world", lists:flatten(Message6)),
                        ok
                end
            },
            {"stopped trace stops and removes its event handler - test sink (gh#267)",
                fun() ->
                        Sink = ?TEST_SINK_EVENT,
                        StartHandlers = gen_event:which_handlers(Sink),
                        {_, T0} = lager_config:get({Sink, loglevel}),
                        StartGlobal = lager_config:global_get(handlers),
                        ?assertEqual([], T0),
                        {ok, TestTrace1} = lager:trace_file("/tmp/test", [{sink, Sink}, {a,b}]),
                        MidHandlers = gen_event:which_handlers(Sink),
                        {ok, TestTrace2} = lager:trace_file("/tmp/test", [{sink, Sink}, {c,d}]),
                        MidHandlers = gen_event:which_handlers(Sink),
                        ?assertEqual(length(StartHandlers)+1, length(MidHandlers)),
                        MidGlobal = lager_config:global_get(handlers),
                        ?assertEqual(length(StartGlobal)+1, length(MidGlobal)),
                        {_, T1} = lager_config:get({Sink, loglevel}),
                        ?assertEqual(2, length(T1)),
                        ok = lager:stop_trace(TestTrace1),
                        {_, T2} = lager_config:get({Sink, loglevel}),
                        ?assertEqual(1, length(T2)),
                        ?assertEqual(length(StartHandlers)+1, length(
                                                                gen_event:which_handlers(Sink))),

                        ?assertEqual(length(StartGlobal)+1, length(lager_config:global_get(handlers))),
                        ok = lager:stop_trace(TestTrace2),
                        EndHandlers = gen_event:which_handlers(Sink),
                        EndGlobal = lager_config:global_get(handlers),
                        {_, T3} = lager_config:get({Sink, loglevel}),
                        ?assertEqual([], T3),
                        ?assertEqual(StartHandlers, EndHandlers),
                        ?assertEqual(StartGlobal, EndGlobal),
                        ok
                end
            },
            {"log messages below the threshold are ignored",
                fun() ->
                        ?assertEqual(0, count(?TEST_SINK_EVENT)),
                        ?TEST_SINK_NAME:debug("this message will be ignored"),
                        ?assertEqual(0, count(?TEST_SINK_EVENT)),
                        ?assertEqual(0, count_ignored(?TEST_SINK_EVENT)),
                        lager_config:set({?TEST_SINK_EVENT, loglevel}, {element(2, lager_util:config_to_mask(debug)), []}),
                        ?TEST_SINK_NAME:debug("this message should be ignored"),
                        ?assertEqual(0, count(?TEST_SINK_EVENT)),
                        ?assertEqual(1, count_ignored(?TEST_SINK_EVENT)),
                        lager:set_loglevel(?TEST_SINK_EVENT, ?MODULE, undefined, debug),
                        ?assertEqual({?DEBUG bor ?INFO bor ?NOTICE bor ?WARNING bor ?ERROR bor ?CRITICAL bor ?ALERT bor ?EMERGENCY, []}, lager_config:get({?TEST_SINK_EVENT, loglevel})),
                        ?TEST_SINK_NAME:debug("this message should be logged"),
                        ?assertEqual(1, count(?TEST_SINK_EVENT)),
                        ?assertEqual(1, count_ignored(?TEST_SINK_EVENT)),
                        ?assertEqual(debug, lager:get_loglevel(?TEST_SINK_EVENT, ?MODULE)),
                        ok
                end
            }
    ]
    }.

setup_sink() ->
    error_logger:tty(false),
    application:load(lager),
    application:set_env(lager, handlers, []),
    application:set_env(lager, error_logger_redirect, false),
    application:set_env(lager, extra_sinks, [{?TEST_SINK_EVENT, [{handlers, [{?MODULE, info}]}]}]),
    lager:start(),
    gen_event:call(lager_event, ?MODULE, flush),
    gen_event:call(?TEST_SINK_EVENT, ?MODULE, flush).

setup() ->
    error_logger:tty(false),
    application:load(lager),
    application:set_env(lager, handlers, [{?MODULE, info}]),
    application:set_env(lager, error_logger_redirect, false),
    lager:start(),
    gen_event:call(lager_event, ?MODULE, flush).

cleanup(_) ->
    application:stop(lager),
    application:stop(goldrush),
    error_logger:tty(true).


crash(Type) ->
    spawn(fun() -> gen_server:call(crash, Type) end),
    timer:sleep(100),
    _ = gen_event:which_handlers(error_logger),
    ok.

test_body(Expected, Actual) ->
    case has_line_numbers() of
        true ->
            ExLen = length(Expected),
            {Body, Rest} = case length(Actual) > ExLen of
                true ->
                    {string:substr(Actual, 1, ExLen),
                        string:substr(Actual, (ExLen + 1))};
                _ ->
                    {Actual, []}
            end,
            ?assertEqual(Expected, Body),
            % OTP-17 (and maybe later releases) may tack on additional info
            % about the failure, so if Actual starts with Expected (already
            % confirmed by having gotten past assertEqual above) and ends
            % with " line NNN" we can ignore what's in-between. By extension,
            % since there may not be line information appended at all, any
            % text we DO find is reportable, but not a test failure.
            case Rest of
                [] ->
                    ok;
                _ ->
                    % isolate the extra data and report it if it's not just
                    % a line number indicator
                    case re:run(Rest, "^.*( line \\d+)$", [{capture, [1]}]) of
                        nomatch ->
                            ?debugFmt(
                                "Trailing data \"~s\" following \"~s\"",
                                [Rest, Expected]);
                        {match, [{0, _}]} ->
                            % the whole sting is " line NNN"
                            ok;
                        {match, [{Off, _}]} ->
                            ?debugFmt(
                                "Trailing data \"~s\" following \"~s\"",
                                [string:substr(Rest, 1, Off), Expected])
                    end
            end;
        _ ->
            ?assertEqual(Expected, Actual)
    end.

error_logger_redirect_crash_setup() ->
    error_logger:tty(false),
    application:load(lager),
    application:set_env(lager, error_logger_redirect, true),
    application:set_env(lager, handlers, [{?MODULE, error}]),
    lager:start(),
    crash:start(),
    lager_event.

error_logger_redirect_crash_setup_sink() ->
    error_logger:tty(false),
    application:load(lager),
    application:set_env(lager, error_logger_redirect, true),
    application:unset_env(lager, handlers),
    application:set_env(lager, extra_sinks, [
        {error_logger_lager_event, [
            {handlers, [{?MODULE, error}]}]}]),
    lager:start(),
    crash:start(),
    error_logger_lager_event.

error_logger_redirect_crash_cleanup(_Sink) ->
    application:stop(lager),
    application:stop(goldrush),
    application:unset_env(lager, extra_sinks),
    case whereis(crash) of
        undefined -> ok;
        Pid -> exit(Pid, kill)
    end,
    error_logger:tty(true).

error_logger_redirect_crash_test_() ->
    TestBody=fun(Name,CrashReason,Expected) -> 
        fun(Sink) ->
            {Name,
                fun() ->
                        Pid = whereis(crash),
                        crash(CrashReason),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        test_body(Expected, lists:flatten(Msg)),
                        ?assertEqual(Pid,proplists:get_value(pid,Metadata)),
                        ?assertEqual(lager_util:level_to_num(error),Level)
                end
            }
        end
    end,
    Tests = [
        fun(Sink) -> 
            {"again, there is nothing up my sleeve",
                fun() ->
                        ?assertEqual(undefined, pop(Sink)),
                        ?assertEqual(0, count(Sink))
                end
            }
        end,

        TestBody("bad return value",bad_return,"gen_server crash terminated with reason: bad return value: bleh"),
        TestBody("bad return value with string",bad_return_string,"gen_server crash terminated with reason: bad return value: {tuple,{tuple,\"string\"}}"),
        TestBody("bad return uncaught throw",throw,"gen_server crash terminated with reason: bad return value: a_ball"),
        TestBody("case clause",case_clause,"gen_server crash terminated with reason: no case clause matching {} in crash:handle_call/3"),
        TestBody("case clause string",case_clause_string,"gen_server crash terminated with reason: no case clause matching \"crash\" in crash:handle_call/3"),
        TestBody("function clause",function_clause,"gen_server crash terminated with reason: no function clause matching crash:function({})"),
        TestBody("if clause",if_clause,"gen_server crash terminated with reason: no true branch found while evaluating if expression in crash:handle_call/3"),
        TestBody("try clause",try_clause,"gen_server crash terminated with reason: no try clause matching [] in crash:handle_call/3"),
        TestBody("undefined function",undef,"gen_server crash terminated with reason: call to undefined function crash:booger/0 from crash:handle_call/3"),
        TestBody("bad math",badarith,"gen_server crash terminated with reason: bad arithmetic expression in crash:handle_call/3"),
        TestBody("bad match",badmatch,"gen_server crash terminated with reason: no match of right hand value {} in crash:handle_call/3"),
        TestBody("bad arity",badarity,"gen_server crash terminated with reason: fun called with wrong arity of 1 instead of 3 in crash:handle_call/3"),
        TestBody("bad arg1",badarg1,"gen_server crash terminated with reason: bad argument in crash:handle_call/3"),
        TestBody("bad arg2",badarg2,"gen_server crash terminated with reason: bad argument in call to erlang:iolist_to_binary([\"foo\",bar]) in crash:handle_call/3"),
        TestBody("bad record",badrecord,"gen_server crash terminated with reason: bad record state in crash:handle_call/3"),
        TestBody("noproc",noproc,"gen_server crash terminated with reason: no such process or port in call to gen_event:call(foo, bar, baz)"),
        TestBody("badfun",badfun,"gen_server crash terminated with reason: bad function booger in crash:handle_call/3")
    ],
    {"Error logger redirect crash", [
        {"Redirect to default sink", 
            {foreach,
            fun error_logger_redirect_crash_setup/0,
            fun error_logger_redirect_crash_cleanup/1,
            Tests}},
        {"Redirect to error_logger_lager_event sink",
            {foreach,
            fun error_logger_redirect_crash_setup_sink/0,
            fun error_logger_redirect_crash_cleanup/1,
            Tests}}
    ]}.


error_logger_redirect_setup() ->
    error_logger:tty(false),
    application:load(lager),
    application:set_env(lager, error_logger_redirect, true),
    application:set_env(lager, handlers, [{?MODULE, info}]),
    lager:start(),
    lager:log(error, self(), "flush flush"),
    timer:sleep(100),
    gen_event:call(lager_event, ?MODULE, flush),
    lager_event.

error_logger_redirect_setup_sink() ->
    error_logger:tty(false),
    application:load(lager),
    application:set_env(lager, error_logger_redirect, true),
    application:unset_env(lager, handlers),
    application:set_env(lager, extra_sinks, [
        {error_logger_lager_event, [
            {handlers, [{?MODULE, info}]}]}]),
    lager:start(),
    lager:log(error_logger_lager_event, error, self(), "flush flush", []),
    timer:sleep(100),
    gen_event:call(error_logger_lager_event, ?MODULE, flush),
    error_logger_lager_event.

error_logger_redirect_cleanup(_) ->
    application:stop(lager),
    application:stop(goldrush),
    application:unset_env(lager, extra_sinks),
    error_logger:tty(true).

error_logger_redirect_test_() ->
    Tests = [
            {"error reports are printed",
                fun(Sink) ->
                        sync_error_logger:error_report([{this, is}, a, {silly, format}]),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(error),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        Expected = "this: is, a, silly: format",
                        ?assertEqual(Expected, lists:flatten(Msg))

                end
            },
            {"string error reports are printed",
                fun(Sink) ->
                        sync_error_logger:error_report("this is less silly"),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(error),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        Expected = "this is less silly",
                        ?assertEqual(Expected, lists:flatten(Msg))
                end
            },
            {"error messages are printed",
                fun(Sink) ->
                        sync_error_logger:error_msg("doom, doom has come upon you all"),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(error),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        Expected = "doom, doom has come upon you all",
                        ?assertEqual(Expected, lists:flatten(Msg))
                end
            },
            {"error messages with unicode characters in Args are printed",
                fun(Sink) ->
                        sync_error_logger:error_msg("~ts", ["Привет!"]),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(error),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        ?assertEqual("Привет!", lists:flatten(Msg))
                end
            },
            {"error messages are truncated at 4096 characters",
                fun(Sink) ->
                        sync_error_logger:error_msg("doom, doom has come upon you all ~p", [string:copies("doom", 10000)]),
                        _ = gen_event:which_handlers(error_logger),
                        {_, _, Msg,_Metadata} = pop(Sink),
                        ?assert(length(lists:flatten(Msg)) < 5100)
                end
            },

            {"info reports are printed",
                fun(Sink) ->
                        sync_error_logger:info_report([{this, is}, a, {silly, format}]),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(info),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        Expected = "this: is, a, silly: format",
                        ?assertEqual(Expected, lists:flatten(Msg))
                end
            },
            {"info reports are truncated at 4096 characters",
                fun(Sink) ->
                        sync_error_logger:info_report([[{this, is}, a, {silly, format}] || _ <- lists:seq(0, 600)]),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(info),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        ?assert(length(lists:flatten(Msg)) < 5000)
                end
            },
            {"single term info reports are printed",
                fun(Sink) ->
                        sync_error_logger:info_report({foolish, bees}),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(info),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        ?assertEqual("{foolish,bees}", lists:flatten(Msg))
                end
            },
            {"single term error reports are printed",
                fun(Sink) ->
                        sync_error_logger:error_report({foolish, bees}),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(error),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        ?assertEqual("{foolish,bees}", lists:flatten(Msg))
                end
            },
            {"string info reports are printed",
                fun(Sink) ->
                        sync_error_logger:info_report("this is less silly"),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(info),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        ?assertEqual("this is less silly", lists:flatten(Msg))
                end
            },
            {"string info reports are truncated at 4096 characters",
                fun(Sink) ->
                        sync_error_logger:info_report(string:copies("this is less silly", 1000)),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(info),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        ?assert(length(lists:flatten(Msg)) < 5100)
                end
            },
            {"strings in a mixed report are printed as strings",
                fun(Sink) ->
                        sync_error_logger:info_report(["this is less silly", {than, "this"}]),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(info),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        ?assertEqual("\"this is less silly\", than: \"this\"", lists:flatten(Msg))
                end
            },
            {"info messages are printed",
                fun(Sink) ->
                        sync_error_logger:info_msg("doom, doom has come upon you all"),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(info),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        ?assertEqual("doom, doom has come upon you all", lists:flatten(Msg))
                end
            },
            {"info messages are truncated at 4096 characters",
                fun(Sink) ->
                        sync_error_logger:info_msg("doom, doom has come upon you all ~p", [string:copies("doom", 10000)]),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(info),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        ?assert(length(lists:flatten(Msg)) < 5100)
                end
            },
            {"info messages with unicode characters in Args are printed",
                fun(Sink) ->
                        sync_error_logger:info_msg("~ts", ["Привет!"]),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(info),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        ?assertEqual("Привет!", lists:flatten(Msg))
                end
            },
            {"warning messages with unicode characters in Args are printed",
                fun(Sink) ->
                        sync_error_logger:warning_msg("~ts", ["Привет!"]),
                        Map = error_logger:warning_map(),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(Map),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        ?assertEqual("Привет!", lists:flatten(Msg))
                end
            },

            {"warning messages are printed at the correct level",
                fun(Sink) ->
                        sync_error_logger:warning_msg("doom, doom has come upon you all"),
                        Map = error_logger:warning_map(),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(Map),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        ?assertEqual("doom, doom has come upon you all", lists:flatten(Msg))
                end
            },
            {"warning reports are printed at the correct level",
                fun(Sink) ->
                        sync_error_logger:warning_report([{i, like}, pie]),
                        Map = error_logger:warning_map(),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(Map),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        ?assertEqual("i: like, pie", lists:flatten(Msg))
                end
            },
            {"single term warning reports are printed at the correct level",
                fun(Sink) ->
                        sync_error_logger:warning_report({foolish, bees}),
                        Map = error_logger:warning_map(),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(Map),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        ?assertEqual("{foolish,bees}", lists:flatten(Msg))
                end
            },
            {"application stop reports",
                fun(Sink) ->
                        sync_error_logger:info_report([{application, foo}, {exited, quittin_time}, {type, lazy}]),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(info),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        ?assertEqual("Application foo exited with reason: quittin_time", lists:flatten(Msg))
                end
            },
            {"supervisor reports",
                fun(Sink) ->
                        sync_error_logger:error_report(supervisor_report, [{errorContext, france}, {offender, [{name, mini_steve}, {mfargs, {a, b, [c]}}, {pid, bleh}]}, {reason, fired}, {supervisor, {local, steve}}]),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(error),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        ?assertEqual("Supervisor steve had child mini_steve started with a:b(c) at bleh exit with reason fired in context france", lists:flatten(Msg))
                end
            },
            {"supervisor reports with real error",
                fun(Sink) ->
                        sync_error_logger:error_report(supervisor_report, [{errorContext, france}, {offender, [{name, mini_steve}, {mfargs, {a, b, [c]}}, {pid, bleh}]}, {reason, {function_clause,[{crash,handle_info,[foo]}]}}, {supervisor, {local, steve}}]),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(error),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        ?assertEqual("Supervisor steve had child mini_steve started with a:b(c) at bleh exit with reason no function clause matching crash:handle_info(foo) in context france", lists:flatten(Msg))
                end
            },

            {"supervisor reports with real error and pid",
                fun(Sink) ->
                        sync_error_logger:error_report(supervisor_report, [{errorContext, france}, {offender, [{name, mini_steve}, {mfargs, {a, b, [c]}}, {pid, bleh}]}, {reason, {function_clause,[{crash,handle_info,[foo]}]}}, {supervisor, somepid}]),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(error),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        ?assertEqual("Supervisor somepid had child mini_steve started with a:b(c) at bleh exit with reason no function clause matching crash:handle_info(foo) in context france", lists:flatten(Msg))
                end
            },

            {"supervisor_bridge reports",
                fun(Sink) ->
                        sync_error_logger:error_report(supervisor_report, [{errorContext, france}, {offender, [{mod, mini_steve}, {pid, bleh}]}, {reason, fired}, {supervisor, {local, steve}}]),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(error),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        ?assertEqual("Supervisor steve had child at module mini_steve at bleh exit with reason fired in context france", lists:flatten(Msg))
                end
            },
            {"application progress report",
                fun(Sink) ->
                        sync_error_logger:info_report(progress, [{application, foo}, {started_at, node()}]),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(info),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        Expected = lists:flatten(io_lib:format("Application foo started on node ~w", [node()])),
                        ?assertEqual(Expected, lists:flatten(Msg))
                end
            },
            {"supervisor progress report",
                fun(Sink) ->
                        lager:set_loglevel(Sink, ?MODULE, undefined, debug),
                        ?assertEqual({?DEBUG bor ?INFO bor ?NOTICE bor ?WARNING bor ?ERROR bor ?CRITICAL bor ?ALERT bor ?EMERGENCY, []}, lager_config:get({Sink, loglevel})),
                        sync_error_logger:info_report(progress, [{supervisor, {local, foo}}, {started, [{mfargs, {foo, bar, 1}}, {pid, baz}]}]),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(debug),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        ?assertEqual("Supervisor foo started foo:bar/1 at pid baz", lists:flatten(Msg))
                end
            },
            {"supervisor progress report with pid",
                fun(Sink) ->
                        lager:set_loglevel(Sink, ?MODULE, undefined, debug),
                        ?assertEqual({?DEBUG bor ?INFO bor ?NOTICE bor ?WARNING bor ?ERROR bor ?CRITICAL bor ?ALERT bor ?EMERGENCY, []}, lager_config:get({Sink, loglevel})),
                        sync_error_logger:info_report(progress, [{supervisor, somepid}, {started, [{mfargs, {foo, bar, 1}}, {pid, baz}]}]),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(debug),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        ?assertEqual("Supervisor somepid started foo:bar/1 at pid baz", lists:flatten(Msg))
                end
            },
            {"crash report for emfile",
                fun(Sink) ->
                        sync_error_logger:error_report(crash_report, [[{pid, self()}, {registered_name, []}, {error_info, {error, emfile, [{stack, trace, 1}]}}], []]),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(error),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        Expected = lists:flatten(io_lib:format("CRASH REPORT Process ~w with 0 neighbours crashed with reason: maximum number of file descriptors exhausted, check ulimit -n", [self()])),
                        ?assertEqual(Expected, lists:flatten(Msg))
                end
            },
            {"crash report for system process limit",
                fun(Sink) ->
                        sync_error_logger:error_report(crash_report, [[{pid, self()}, {registered_name, []}, {error_info, {error, system_limit, [{erlang, spawn, 1}]}}], []]),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(error),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        Expected = lists:flatten(io_lib:format("CRASH REPORT Process ~w with 0 neighbours crashed with reason: system limit: maximum number of processes exceeded", [self()])),
                        ?assertEqual(Expected, lists:flatten(Msg))
                end
            },
            {"crash report for system process limit2",
                fun(Sink) ->
                        sync_error_logger:error_report(crash_report, [[{pid, self()}, {registered_name, []}, {error_info, {error, system_limit, [{erlang, spawn_opt, 1}]}}], []]),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(error),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        Expected = lists:flatten(io_lib:format("CRASH REPORT Process ~w with 0 neighbours crashed with reason: system limit: maximum number of processes exceeded", [self()])),
                        ?assertEqual(Expected, lists:flatten(Msg))
                end
            },
            {"crash report for system port limit",
                fun(Sink) ->
                        sync_error_logger:error_report(crash_report, [[{pid, self()}, {registered_name, []}, {error_info, {error, system_limit, [{erlang, open_port, 1}]}}], []]),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(error),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        Expected = lists:flatten(io_lib:format("CRASH REPORT Process ~w with 0 neighbours crashed with reason: system limit: maximum number of ports exceeded", [self()])),
                        ?assertEqual(Expected, lists:flatten(Msg))
                end
            },
            {"crash report for system port limit",
                fun(Sink) ->
                        sync_error_logger:error_report(crash_report, [[{pid, self()}, {registered_name, []}, {error_info, {error, system_limit, [{erlang, list_to_atom, 1}]}}], []]),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(error),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        Expected = lists:flatten(io_lib:format("CRASH REPORT Process ~w with 0 neighbours crashed with reason: system limit: tried to create an atom larger than 255, or maximum atom count exceeded", [self()])),
                        ?assertEqual(Expected, lists:flatten(Msg))
                end
            },
            {"crash report for system ets table limit",
                fun(Sink) ->
                        sync_error_logger:error_report(crash_report, [[{pid, self()}, {registered_name, test}, {error_info, {error, system_limit, [{ets,new,[segment_offsets,[ordered_set,public]]},{mi_segment,open_write,1},{mi_buffer_converter,handle_cast,2},{gen_server,handle_msg,5},{proc_lib,init_p_do_apply,3}]}}], []]),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(error),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        Expected = lists:flatten(io_lib:format("CRASH REPORT Process ~w with 0 neighbours crashed with reason: system limit: maximum number of ETS tables exceeded", [test])),
                        ?assertEqual(Expected, lists:flatten(Msg))
                end
            },
            {"crash report for unknown system limit should be truncated at 500 characters",
                fun(Sink) ->
                        sync_error_logger:error_report(crash_report, [[{pid, self()}, {error_info, {error, system_limit, [{wtf,boom,[string:copies("aaaa", 4096)]}]}}], []]),
                        _ = gen_event:which_handlers(error_logger),
                        {_, _, Msg,_Metadata} = pop(Sink),
                        ?assert(length(lists:flatten(Msg)) > 550),
                        ?assert(length(lists:flatten(Msg)) < 600)
                end
            },
            {"crash reports for 'special processes' should be handled right - function_clause",
                fun(Sink) ->
                        {ok, Pid} = special_process:start(),
                        unlink(Pid),
                        Pid ! function_clause,
                        timer:sleep(500),
                        _ = gen_event:which_handlers(error_logger),
                        {_, _, Msg, _Metadata} = pop(Sink),
                        Expected = lists:flatten(io_lib:format("CRASH REPORT Process ~p with 0 neighbours crashed with reason: no function clause matching special_process:foo(bar)",
                                [Pid])),
                        test_body(Expected, lists:flatten(Msg))
                end
            },
            {"crash reports for 'special processes' should be handled right - case_clause",
                fun(Sink) ->
                        {ok, Pid} = special_process:start(),
                        unlink(Pid),
                        Pid ! {case_clause, wtf},
                        timer:sleep(500),
                        _ = gen_event:which_handlers(error_logger),
                        {_, _, Msg, _Metadata} = pop(Sink),
                        Expected = lists:flatten(io_lib:format("CRASH REPORT Process ~p with 0 neighbours crashed with reason: no case clause matching wtf in special_process:loop/0",
                                [Pid])),
                        test_body(Expected, lists:flatten(Msg))
                end
            },
            {"crash reports for 'special processes' should be handled right - exit",
                fun(Sink) ->
                        {ok, Pid} = special_process:start(),
                        unlink(Pid),
                        Pid ! exit,
                        timer:sleep(500),
                        _ = gen_event:which_handlers(error_logger),
                        {_, _, Msg, _Metadata} = pop(Sink),
                        Expected = lists:flatten(io_lib:format("CRASH REPORT Process ~p with 0 neighbours exited with reason: byebye in special_process:loop/0",
                                [Pid])),
                        test_body(Expected, lists:flatten(Msg))
                end
            },
            {"crash reports for 'special processes' should be handled right - error",
                fun(Sink) ->
                        {ok, Pid} = special_process:start(),
                        unlink(Pid),
                        Pid ! error,
                        timer:sleep(500),
                        _ = gen_event:which_handlers(error_logger),
                        {_, _, Msg, _Metadata} = pop(Sink),
                        Expected = lists:flatten(io_lib:format("CRASH REPORT Process ~p with 0 neighbours crashed with reason: mybad in special_process:loop/0",
                                [Pid])),
                        test_body(Expected, lists:flatten(Msg))
                end
            },
            {"webmachine error reports",
                fun(Sink) ->
                        Path = "/cgi-bin/phpmyadmin",
                        Reason = {error,{error,{badmatch,{error,timeout}},
                                        [{myapp,dostuff,2,[{file,"src/myapp.erl"},{line,123}]},
                                         {webmachine_resource,resource_call,3,[{file,"src/webmachine_resource.erl"},{line,169}]}]}},
                        sync_error_logger:error_msg("webmachine error: path=~p~n~p~n", [Path, Reason]),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(error),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        ?assertEqual("Webmachine error at path \"/cgi-bin/phpmyadmin\" : no match of right hand value {error,timeout} in myapp:dostuff/2 line 123", lists:flatten(Msg))

                end
            },
            {"Cowboy error reports, 8 arg version",
             fun(Sink) ->
                        Stack = [{my_handler,init, 3,[{file,"src/my_handler.erl"},{line,123}]},
                                 {cowboy_handler,handler_init,4,[{file,"src/cowboy_handler.erl"},{line,169}]}],

                        sync_error_logger:error_msg(
                            "** Cowboy handler ~p terminating in ~p/~p~n"
                            "   for the reason ~p:~p~n"
                            "** Options were ~p~n"
                            "** Request was ~p~n"
                            "** Stacktrace: ~p~n~n",
                            [my_handler, init, 3, error, {badmatch, {error, timeout}}, [],
                             "Request", Stack]),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(error),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        ?assertEqual("Cowboy handler my_handler terminated in my_handler:init/3 with reason: no match of right hand value {error,timeout} in my_handler:init/3 line 123", lists:flatten(Msg))
                end
            },
            {"Cowboy error reports, 10 arg version",
             fun(Sink) ->
                        Stack = [{my_handler,somecallback, 3,[{file,"src/my_handler.erl"},{line,123}]},
                                 {cowboy_handler,handler_init,4,[{file,"src/cowboy_handler.erl"},{line,169}]}],
                        sync_error_logger:error_msg(
                            "** Cowboy handler ~p terminating in ~p/~p~n"
                            "   for the reason ~p:~p~n** Message was ~p~n"
                            "** Options were ~p~n** Handler state was ~p~n"
                            "** Request was ~p~n** Stacktrace: ~p~n~n",
                            [my_handler, somecallback, 3, error, {badmatch, {error, timeout}}, hello, [],
                             {}, "Request", Stack]),

                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(error),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        ?assertEqual("Cowboy handler my_handler terminated in my_handler:somecallback/3 with reason: no match of right hand value {error,timeout} in my_handler:somecallback/3 line 123", lists:flatten(Msg))
                end
            },
            {"Cowboy error reports, 5 arg version",
             fun(Sink) ->
                        sync_error_logger:error_msg(
                            "** Cowboy handler ~p terminating; "
                            "function ~p/~p was not exported~n"
                            "** Request was ~p~n** State was ~p~n~n",
                            [my_handler, to_json, 2, "Request", {}]),
                        _ = gen_event:which_handlers(error_logger),
                        {Level, _, Msg,Metadata} = pop(Sink),
                        ?assertEqual(lager_util:level_to_num(error),Level),
                        ?assertEqual(self(),proplists:get_value(pid,Metadata)),
                        ?assertEqual("Cowboy handler my_handler terminated with reason: call to undefined function my_handler:to_json/2", lists:flatten(Msg))
                end
            },
            {"messages should not be generated if they don't satisfy the threshold",
                fun(Sink) ->
                        lager:set_loglevel(Sink, ?MODULE, undefined, error),
                        ?assertEqual({?ERROR bor ?CRITICAL bor ?ALERT bor ?EMERGENCY, []}, lager_config:get({Sink, loglevel})),
                        sync_error_logger:info_report([hello, world]),
                        _ = gen_event:which_handlers(error_logger),
                        ?assertEqual(0, count(Sink)),
                        ?assertEqual(0, count_ignored(Sink)),
                        lager:set_loglevel(Sink, ?MODULE, undefined, info),
                        ?assertEqual({?INFO bor ?NOTICE bor ?WARNING bor ?ERROR bor ?CRITICAL bor ?ALERT bor ?EMERGENCY, []}, lager_config:get({Sink, loglevel})),
                        sync_error_logger:info_report([hello, world]),
                        _ = gen_event:which_handlers(error_logger),
                        ?assertEqual(1, count(Sink)),
                        ?assertEqual(0, count_ignored(Sink)),
                        lager:set_loglevel(Sink, ?MODULE, undefined, error),
                        ?assertEqual({?ERROR bor ?CRITICAL bor ?ALERT bor ?EMERGENCY, []}, lager_config:get({Sink, loglevel})),
                        lager_config:set({Sink, loglevel}, {element(2, lager_util:config_to_mask(debug)), []}),
                        sync_error_logger:info_report([hello, world]),
                        _ = gen_event:which_handlers(error_logger),
                        ?assertEqual(1, count(Sink)),
                        ?assertEqual(1, count_ignored(Sink))
                end
            }
        ],
    SinkTests = lists:map(
        fun({Name, F}) ->
            fun(Sink) -> {Name, fun() -> F(Sink) end} end
        end,
        Tests),
    {"Error logger redirect", [
        {"Redirect to default sink", 
            {foreach,
            fun error_logger_redirect_setup/0,
            fun error_logger_redirect_cleanup/1,
            SinkTests}},
        {"Redirect to error_logger_lager_event sink",
            {foreach,
            fun error_logger_redirect_setup_sink/0,
            fun error_logger_redirect_cleanup/1,
            SinkTests}}
    ]}.

safe_format_test() ->
    ?assertEqual("foo bar", lists:flatten(lager:safe_format("~p ~p", [foo, bar], 1024))),
    ?assertEqual("FORMAT ERROR: \"~p ~p ~p\" [foo,bar]", lists:flatten(lager:safe_format("~p ~p ~p", [foo, bar], 1024))),
    ok.

unsafe_format_test() ->
    ?assertEqual("foo bar", lists:flatten(lager:unsafe_format("~p ~p", [foo, bar]))),
    ?assertEqual("FORMAT ERROR: \"~p ~p ~p\" [foo,bar]", lists:flatten(lager:unsafe_format("~p ~p ~p", [foo, bar]))),
    ok.

async_threshold_test_() ->
    {foreach,
        fun() ->
                error_logger:tty(false),
                ets:new(async_threshold_test, [set, named_table, public]),
                ets:insert_new(async_threshold_test, {sync_toggled, 0}),
                ets:insert_new(async_threshold_test, {async_toggled, 0}),
                application:load(lager),
                application:set_env(lager, error_logger_redirect, false),
                application:set_env(lager, async_threshold, 2),
                application:set_env(lager, async_threshold_window, 1),
                application:set_env(lager, handlers, [{?MODULE, info}]),
                lager:start()
        end,
        fun(_) ->
                application:unset_env(lager, async_threshold),
                application:stop(lager),
                application:stop(goldrush),
                ets:delete(async_threshold_test),
                error_logger:tty(true)
        end,
        [
            {"async threshold works",
                fun() ->
                        %% we start out async
                        ?assertEqual(true, lager_config:get(async)),

                        %% put a ton of things in the queue
                        Workers = [spawn_monitor(fun() -> [lager:info("hello world") || _ <- lists:seq(1, 1000)] end) || _ <- lists:seq(1, 15)],

                        %% serialize on mailbox
                        _ = gen_event:which_handlers(lager_event),
                        timer:sleep(500),

                        %% By now the flood of messages will have
                        %% forced the backend throttle to turn off
                        %% async mode, but it's possible all
                        %% outstanding requests have been processed,
                        %% so checking the current status (sync or
                        %% async) is an exercise in race control.

                        %% Instead, we'll see whether the backend
                        %% throttle has toggled into sync mode at any
                        %% point in the past
                        ?assertMatch([{sync_toggled, N}] when N > 0,
                                                              ets:lookup(async_threshold_test, sync_toggled)),
                        %% wait for all the workers to return, meaning that all the messages have been logged (since we're definitely in sync mode at the end of the run)
                        collect_workers(Workers),
                        %% serialize on the mailbox again
                        _ = gen_event:which_handlers(lager_event),
                        %% just in case...
                        timer:sleep(1000),
                        lager:info("hello world"),
                        _ = gen_event:which_handlers(lager_event),

                        %% async is true again now that the mailbox has drained
                        ?assertEqual(true, lager_config:get(async)),
                        ok
                end
            }
        ]
    }.

collect_workers([]) ->
    ok;
collect_workers(Workers) ->
    receive
        {'DOWN', Ref, _, _, _} ->
            collect_workers(lists:keydelete(Ref, 2, Workers))
    end.

produce_n_error_logger_msgs(N) ->
    lists:foreach(fun (K) ->
            error_logger:error_msg("Foo ~p!", [K])
        end,
        lists:seq(0, N-1)
    ).

high_watermark_test_() ->
    {foreach,
        fun() ->
            error_logger:tty(false),
            application:load(lager),
            application:set_env(lager, error_logger_redirect, true),
            application:set_env(lager, handlers, [{lager_test_backend, info}]),
            application:set_env(lager, async_threshold, undefined),
            lager:start()
        end,
        fun(_) ->
            application:stop(lager),
            error_logger:tty(true)
        end,
        [
            {"Nothing dropped when error_logger high watermark is undefined",
                fun () ->
                    ok = error_logger_lager_h:set_high_water(undefined),
                    timer:sleep(100),
                    produce_n_error_logger_msgs(10),
                    timer:sleep(500),
                    ?assert(count() >= 10)
                end
            },
            {"Mostly dropped according to error_logger high watermark",
                fun () ->
                    ok = error_logger_lager_h:set_high_water(5),
                    timer:sleep(100),
                    produce_n_error_logger_msgs(50),
                    timer:sleep(1000),
                    ?assert(count() < 20)
                end
            },
            {"Non-notifications are not dropped",
                fun () ->
                    ok = error_logger_lager_h:set_high_water(2),
                    timer:sleep(100),
                    spawn(fun () -> produce_n_error_logger_msgs(300) end),
                    timer:sleep(50),
                    %% if everything were dropped, this call would be dropped
                    %% too, so lets hope it's not
                    ?assert(is_integer(count())),
                    timer:sleep(1000),
                    ?assert(count() < 10)
                end
            }
        ]
    }.

-endif.