[Flutter] Make Mock file in lib folder by using build_runner and Mockito package

Outline
Create Mock in the lib folder
build.yaml file
Completed

Outline

In Flutter, sometimes we use the build_runner package to generate the code we need for development. In particular, when making a test code, we often use Mockito to make a test Mock.

build_runner: https://pub.dev/packages/build_runner
Mockito: https://pub.dev/packages/mockito

In this blog post, I will introduce how to use the build_runner and Mockito packages to make a Mock file in the lib folder.

Create Mock in the lib folder

Normally, we use the build_runner and Mockito packages to genrate the Mocke for testing, so we can’t use them in the files in the lib folder. However, when making a package for other users like me, we sometimes use Mock in the files in the lib folder as follows.

run_with_network_images/lib/src/run_with_network_images.dart

...
@GenerateMocks([
  HttpClient,
  HttpClientRequest,
  HttpClientResponse,
  HttpHeaders,
  StreamSubscription,
])
R runWithNetworkImages<R>(R Function() body) {
  return HttpOverrides.runZoned(
    body,
    createHttpClient: (_) => _createMockImageHttpClient(),
  );
}
...

In this blog post, I will show you how to make a Mock in the lib folder like this.

build.yaml file

The build_runner can be configured with the build.yaml file. With this build.yaml file, you can also make a Mock in the files in the lib folder.

So, to make a Mock in the files in the lib folder, create a build.yaml file in the root directory of the project and modify it as follows.

targets:
  $default:
    builders:
      mockito|mockBuilder:
        generate_for:
          - 'lib/src/run_with_network_images.dart'

As above, when you specify the file in the lib folder for the target of the Mock generated by Mockito in the build.yaml file, you can also make a Mock in the files in the lib folder.

Completed

Done! we’ve seen how to generate the Mock file in the lib folder by using the build_runner and Mockito packages. This is not often the case, but it is good to know that you can configure the build_runner with the build.yaml file.

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