I'm not quite sure about the origin of these errors but I tried to run tests and they failed

rebar get
==> mzmetrics (get-deps)
...
rebar compile
==> goldrush (compile)
...
rebar eunit
==> goldrush (eunit)
...
18:43:58.313 [info] Application lager started on node nonode@nohost

=INFO REPORT==== 16-Mar-2016::18:43:58 ===
application: lager
exited: stopped
type: permanent

=INFO REPORT==== 16-Mar-2016::18:43:58 ===
application: goldrush
exited: stopped
type: permanent
lager_test_backend: error_logger_redirect_crash_test_ (bad return value)...failed
in function lager_test_backend:has_line_numbers/0 (test/lager_test_backend.erl, line 112)
in call from lager_test_backend:test_body/2 (test/lager_test_backend.erl, line 580)
in call from lager_test_backend:'-error_logger_redirect_crash_test_/0-fun-2-'/2 (test/lager_test_backend.erl, line 606)
error:{badmatch,nomatch}
output:<<"">>
...
lager_test_backend: error_logger_redirect_test (crash reports for 'special processes' should be handled right - function_clause)..._failed
in function lager_test_backend:has_line_numbers/0 (test/lager_test_backend.erl, line 112)
in call from lager_test_backend:test_body/2 (test/lager_test_backend.erl, line 580)
**error:{badmatch,nomatch}
output:<<"">>

lager_test_backend: error_logger_redirect_test_ (crash reports for 'special processes' should be handled right - case_clause)...failed
in function lager_test_backend:has_line_numbers/0 (test/lager_test_backend.erl, line 112)
in call from lager_test_backend:test_body/2 (test/lager_test_backend.erl, line 580)
**error:{badmatch,nomatch}
output:<<"">>

lager_test_backend: error_logger_redirect_test_ (crash reports for 'special processes' should be handled right - exit)...failed
in function lager_test_backend:has_line_numbers/0 (test/lager_test_backend.erl, line 112)
in call from lager_test_backend:test_body/2 (test/lager_test_backend.erl, line 580)
**error:{badmatch,nomatch}
output:<<"">>

lager_test_backend: error_logger_redirect_test_ (crash reports for 'special processes' should be handled right - error)...failed
in function lager_test_backend:has_line_numbers/0 (test/lager_test_backend.erl, line 112)
in call from lager_test_backend:test_body/2 (test/lager_test_backend.erl, line 580)
**error:{badmatch,nomatch}
output:<<"">>

lager_file_backend: filesystem_test_ (tracing with options should work)...failed
in function lager_file_backend:'-filesystem_test_/0-fun-65-'/0 (src/lager_file_backend.erl, line 718)
**error:{assert,[{module,lager_file_backend},
{line,718},
{expression,"filelib : is_regular ( "foo.log.0" )"},
{expected,true},
{value,false}]}
output:<<"">>

Failed: 25. Skipped: 0. Passed: 159.
Cover analysis: mzmetrics/deps/lager/.eunit/index.html
ERROR: One or more eunit tests failed.
ERROR: eunit failed while processing mzmetrics/deps/lager: rebar_abort

what is the advantage of using mzmetrics comparedto simply using ets counters?