See the  example/integration_test directory for an example.

Native unit tests.
Just as Dart unit tests can test the Dart portions
of a plugin in isolation, native unit tests can
test the native parts in isolation.
Each platform has its own native unit test system,
and the tests are written in the same native languages
as the code it is testing.

    Native unit tests can be especially valuable
if you need to mock out APIs wrapped by your plugin code,
which isn’t possible in a Dart integration test.

    You can set up and use any native test frameworks
you are familiar with for each platform,
but the following are already configured in the plugin template: