eurls containing calls to os:cmd fail in Mac OSX 10.6 - erlang

Question

I have just 'inherited' an OTP project in my workplace and I am having the following problem:
A set of tests include a call to a function which uses os:cmd and it seems the reason the tests fail, it's the only difference I have located between failing and successful tests. I am running the tests on Mac OS X 10.6.8 and Erlang 14A.
These are the failing functions:
execute_shell_command(Config, Event, Params, output) ->
execute_with_output(Config, Event, Params);
execute_shell_command(Config, Event, Params, status) ->
execute_with_status(Config, Event, Params).
execute_with_output(Config, Event, Params) ->
Command = executable(Config, Event),
String = string:join([Command|Params], " "),
error_logger:info_msg("Command to be invoked:~n~p", [String]),
os:cmd(String).
And below are the failing tests:
execute_with_output_test() ->
Config = [{click, [{log_path, "fixtures"}, {executable, "echo"}]},
{processing_stat_path, "fixtures"}],
?assertMatch("OK", execute_with_output(Config, click, ["-n", "OK"])).
execute_with_output_success_test() ->
Config = [{click, [{log_path, "fixtures"}, {executable, "true"}]},
{processing_stat_path, "fixtures"}],
?assertMatch("success", execute_with_output(Config, click,
[status_as_output_suffix()])).
execute_with_output_failure_test() ->
Config = [{click, [{log_path, "fixtures"}, {executable, "false"}]},
{processing_stat_path, "fixtures"}],
?assertMatch("error", execute_with_output(Config, click,
[status_as_output_suffix()])).
execute_with_status_success_test() ->
Config = [{click, [{log_path, "fixtures"}, {executable, "true"}]},
{processing_stat_path, "fixtures"}],
?assertMatch(ok, execute_with_status(Config, click, [])).
execute_with_status_failure_test() ->
Config = [{click, [{log_path, "fixtures"}, {executable, "false"}]},
{processing_stat_path, "fixtures"}],
?assertMatch(error, execute_with_status(Config, click, [])).
hdfs_put_command_parameters_echoed_test() ->
Config = [{click, [{log_path, "fixtures"},
{executable, "echo -n"},
{delete_after_copy, false},
{hdfs_url, "hdfs://localhost/unprocessed/clicks"}]},
{processing_stat_path, "fixtures"}],
{ok, Hostname} = inet:gethostname(),
Expected = "fs -put test_file hdfs://localhost/unprocessed/clicks/" ++ Hostname ++ "-test_file",
?assertMatch(Expected, hdfs_put_command(Config, click, "test_file", output)).
click_upload_success_test() ->
Config = [{click, [{log_path, "fixtures"},
{executable, "fixtures/hadoop_mock_success"},
{delete_after_copy, false},
{hdfs_url, "hdfs://testhost"}]},
{processing_state_path, "fixtures"}],
unconsult(configuration_file(test), Config),
Callback = click_upload(test),
?assertMatch([ok, ok], Callback(click, test_message)),
write_last_processed(Config, click, "click-2009-04-10-17-00").
The output of the test suite
erl -noshell -setcookie colonel_hathi -sname test_units_talkative_client -eval 'error_logger:tty(false).' -pa ./ebin -eval 'case lists:member({test,0}, hdfs_loader:module_info(exports)) of true -> hdfs_loader:test(); false -> io:format(" [No test in ~p]~n", [hdfs_loader]) end' -eval 'case lists:member({test,0}, talkative_client_app:module_info(exports)) of true -> talkative_client_app:test(); false -> io:format(" [No test in ~p]~n", [talkative_client_app]) end' -eval 'case lists:member({test,0}, talkative_client_connection:module_info(exports)) of true -> talkative_client_connection:test(); false -> io:format(" [No test in ~p]~n", [talkative_client_connection]) end' -eval 'case lists:member({test,0}, talkative_client_control:module_info(exports)) of true -> talkative_client_control:test(); false -> io:format(" [No test in ~p]~n", [talkative_client_control]) end' -eval 'case lists:member({test,0}, talkative_client_sup:module_info(exports)) of true -> talkative_client_sup:test(); false -> io:format(" [No test in ~p]~n", [talkative_client_sup]) end' -s init stop
hdfs_loader: execute_with_output_test...*failed*
::error:{assertMatch_failed,
[{module,hdfs_loader},
{line,310},
{expression,
"execute_with_output ( Config , click , [ \"-n\" , \"OK\" ] )"},
{expected,"\"OK\""},
{value,"-n OK\n"}]}
in function hdfs_loader:'-execute_with_output_test/0-fun-0-'/0
hdfs_loader: execute_with_output_success_test...*failed*
::error:{assertMatch_failed,
[{module,hdfs_loader},
{line,315},
{expression,
"execute_with_output ( Config , click , [ status_as_output_suffix ( ) ] )"},
{expected,"\"success\""},
{value,"-n success\n"}]}
in function hdfs_loader:'-execute_with_output_success_test/0-fun-0-'/0
hdfs_loader: execute_with_output_failure_test...*failed*
::error:{assertMatch_failed,
[{module,hdfs_loader},
{line,321},
{expression,
"execute_with_output ( Config , click , [ status_as_output_suffix ( ) ] )"},
{expected,"\"error\""},
{value,"-n error\n"}]}
in function hdfs_loader:'-execute_with_output_failure_test/0-fun-0-'/0
hdfs_loader: execute_with_status_success_test...*failed*
::error:{assertMatch_failed,
[{module,hdfs_loader},
{line,327},
{expression,"execute_with_status ( Config , click , [ ] )"},
{expected,"ok"},
{value,"-n success\n"}]}
in function hdfs_loader:'-execute_with_status_success_test/0-fun-0-'/0
hdfs_loader: execute_with_status_failure_test...*failed*
::error:{assertMatch_failed,
[{module,hdfs_loader},
{line,332},
{expression,"execute_with_status ( Config , click , [ ] )"},
{expected,"error"},
{value,"-n error\n"}]}
in function hdfs_loader:'-execute_with_status_failure_test/0-fun-0-'/0
hdfs_loader: hdfs_put_command_parameters_echoed_test...*failed*
::error:{assertMatch_failed,
[{module,hdfs_loader},
{line,342},
{expression,
"hdfs_put_command ( Config , click , \"test_file\" , output )"},
{expected,"Expected"},
{value,
"-n fs -put test_file hdfs://localhost/unprocessed/clicks/ws-dhcp_3_156-test_file\n"}]}
in function hdfs_loader:'-hdfs_put_command_parameters_echoed_test/0-fun-0-'/1
hdfs_loader: click_upload_success_test...*failed*
::error:{assertMatch_failed,[{module,hdfs_loader},
{line,352},
{expression,"Callback ( click , test_message )"},
{expected,"[ ok , ok ]"},
{value,[error,error]}]}
in function hdfs_loader:'-click_upload_success_test/0-fun-0-'/1
in call from hdfs_loader:click_upload_success_test/0
=======================================================
Failed: 7. Skipped: 0. Passed: 17.
All 5 tests passed.
All 46 tests passed.
[No test in talkative_client_control]
rake aborted!
Tests failed
Any help appreciated!

Answer 1

On a Linux box:
1> os:cmd(["echo -n test"]).
"test"
2> os:cmd(["echo test"]).
"test\n"
echo behaves differently on Mac. Specifically, -n doesn't work by default. Here might be a possible solution: http://hints.macworld.com/article.php?story=20071106192548833
Another solution is to stop using -n in the tests and either strip or match on the newline character.