TestHarness<T extends ApplicationChannel> class Null safety

Manages application lifecycle for the purpose of testing the application.

You install a test harness at the beginning of a test's main function. Before test cases are run, the harness starts an instance of your application on the same isolate as the tests. After your tests complete, the harness stops the application from running.

You typically create a subclass of TestHarness that is used for all tests in an application. The subclass overrides callbacks beforeStart and afterStart to configure the application. This configuration might be adding an application's database schema to a test database, or to create OAuth2 client identifiers for use during test. See also TestHarnessORMMixin and TestHarnessAuthMixin for adding common behaviors like these to your harness.

Usage:

    class Harness extends ApplicationHarness<MyChannel> {
      @override
      Future afterStart() async {
        channel.service.uri = Uri.parse("http://localhost:4040");
      }
    }

    void main() {
      final harness = Harness()..install();

      test("GET /example returns 200", () async {
        final response = await harness.agent.get("/example");
        expectResponse(response, 200);
      });
    }