Determining Test Coverage in Go Integration Tests

Integration tests aim to evaluate the functionality of a system as a whole, often by mocking or controlling external dependencies. However, determining the test coverage of integration tests poses unique challenges.

Measuring Coverage in Non-Package Tests

In the scenario described, the tests are separate from the packages they test. Consequently, the go test -cover command reports 0% coverage. To address this, one can utilize the -coverpkg directive.

Using -coverpkg for Specific Package Coverage

The -coverpkg directive enables the measurement of test coverage in a specified package, even if the tests are external. It takes the package path as its argument.

For instance, the following command measures the coverage of the mypackage package:

$ go test -cover -coverpkg mypackage ./src/api/...

This approach allows for the targeted analysis of package coverage in integration tests.

Example Coverage Output

Consider an example where the api package contains tests in main_test.go. Most of the business logic resides in the mypackage package. Executing the command with -coverpkg provides a more accurate representation of coverage:

$ go test -cover -coverpkg mypackage ./src/api/...
ok      /api    0.190s  coverage: 50.8% of statements in mypackage
ok      /api/mypackage   0.022s  coverage: 0.7% of statements in mypackage

This output shows that the tests cover 50.8% of the statements in the mypackage package. In contrast, without using -coverpkg, the coverage would appear higher at 71.0%, which is due to tests outside of the specified package.

Additional Considerations

It's worth noting that integration tests typically cover less code than unit tests due to the complexity of mocking and the nature of system-wide testing. However, the approach outlined above provides a way to measure the actual coverage of integration tests specifically for relevant packages.