Testing

Types of tests

Multiple Dart test targets are available:

• dart_fuchsia_test runs the test as a package on a fuchsia device. This must be used if there is anything fuchsia specific being used like fidl. It is run with fx test.
• dart_test runs unit tests that can be run on the host or on a fuchsia device. The dart:ui package is not made available to these tests. The test can be run with fx tests --host.
• flutter_test is just like dart_test except the dart:ui package is made available to it, so it can test widget code.

Note that in order to be built and run on bots, the test targets need to be included in the packages that are configured to run there. For example, in sdk this can be achieved by adding those tests to //sdk:tests.

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.