elixir-test-runner

ExUnit supports line-based test selection using the syntax mix test test/path/to/file_test.exs:LINE_NUMBER. This runs only the test defined at that line, useful for focused debugging without executing the full suite.

Yes, ExUnit filtering allows narrowing tests by tags (mix test --only tag_name) and module patterns. This reduces execution time by running only relevant tests across your project or umbrella apps.

Umbrella projects require targeted test execution across multiple apps. ExUnit filtering by app name or file path lets you run tests for specific sub-applications without running the entire suite.

ExUnit provides verbose failure reporting and trace options to surface detailed error context. These debugging aids help identify root causes faster than standard failure summaries, especially in complex test scenarios.

ExUnit includes built-in coverage reporting that tracks which code paths are tested. Running mix test with coverage flags generates reports showing tested and untested areas across your codebase.