I find some aspects of the way that PhutilUnitTestEngine works to be counter-intuitive (this might extend to other ArcanistUnitTestEngine subclasses as well). Specifically, it is not possible to execute a single test path. I would expect that arc unit -- src/lint/linter/__tests__/ArcanistChmodLinterTestCase.php would execute only the tests in the ArcanistChmodLinterTestCase class, but instead it executes all tests in the src/lint/linter/__tests__/ directory. This can be annoying when writing new tests (especially tests for linters) because it slows down the ability of running the tests.