The dart_test target is appropriate for unit tests. Each target yields a test script in the output directory under:


This script simply runs the given tests in the Flutter shell on the host.

The //scripts/run-dart-action.py script may be used to run multiple test suites at once:

scripts/run-dart-action.py test --out out/<build-type> --tree //topaz/shell/*

It also works with a single suite:

scripts/run-dart-action.py test --out out/<build-type> --tree //topaz/shell/armadillo:test

Code coverage

To generate an HTML coverage report from all dart_tests, first build them with fx build and then run:

scripts/dart/report_coverage.py --report-dir ...

This script runs all of the dart tests in your <out>/host_tests/ dir with coverage enabled. Under the hood, each test uses the coverage collection support from flutter.

The basic logic is:

for test in host_tests:
  covered_lines += lines in test's package that were covered by test
  total_lines += all lines in test's package

So if there are packages that have no tests at all, they won't be considered in the denominator of the report, which can give you a misleadingly high coverage number.