Currently, arc unit --coverage will report coverage data for files which don't have any coverage data available. For example, see D15251. When running arc unit for this diff, the following output is shown:
PASS 51ms ArcanistLibraryTestCase::testTrue
PASS 1.8s ArcanistLibraryTestCase::testMethodVisibility
PASS 72ms ArcanistLibraryTestCase::testEverythingImplemented
PASS 367ms ArcanistLibraryTestCase::testLibraryMap
COVERAGE REPORT
0% bar
0% foo
100% src/__tests__/ArcanistLibraryTestCase.phpThis doesn't appear to be unique to any specific test engine but seems to be due to the following code within ArcanistUnitWorkflow:
if ($coverage) { $file_coverage = array_fill_keys( $paths, 0); $file_reports = array(); foreach ($coverage as $file => $reports) { $report = ArcanistUnitTestResult::mergeCoverage($reports); $cov = substr_count($report, 'C'); $uncov = substr_count($report, 'U'); if ($cov + $uncov) { $coverage = $cov / ($cov + $uncov); } else { $coverage = 0; } $file_coverage[$file] = $coverage; $file_reports[$file] = $report; }