mocking a class used by a Gradle plugin when testing

Question

I'm writing a Gradle plugin that interacts with an external HTTP API. This interaction is handled by a single class (let's call it ApiClient). I'm writing some high-level tests that use Gradle TestKit to simulate an entire build that uses the plugin, but I obviously don't want them to actually hit the API. Instead, I'd like to mock ApiClient and check that its methods have been called with the appropriate arguments, but I'm not sure how to actually inject the mocked version into the plugin. The plugin is instantiated somewhere deep within Gradle, and gets applied to the project being executed using its void apply(Project project) method, so there doesn't appear to be a way to inject a MockApiClient object.

Perhaps one way is to manually instantiate a Project, apply() the plugin to it (at which point, I can inject the mocked object because I have control over plugin instantiation), and then programmatically execute a task on the project, but how can I do that? I've read the Gradle API documentation and haven't seen an obvious way.

A worst-case solution will be to pass in a debug flag through the plugin extension configuration, which the plugin will then use to determine whether it should use the real ApiClient or a mock (which would print some easily grep-able messages to the STDOUT). This isn't ideal, though, since it's more fuzzy than checking the arguments actually passed to the ApiClient methods.

Answer 1

Perhaps you could split your plugin into a few different plugins

• my-plugin-common - All the common stuff
• my-plugin-real-services - Adds the "real" services to the model (eg RealApiClient)
• my-plugin-mock-services - Adds "mock" services to the model (eg MockApiClient)
• my-plugin - Applies my-plugin-real-services and my-plugin-common
• my-plugin-mock - Applies my-plugin-mock-services and my-plugin-common

In the real world, people will only ever apply: 'my-plugin'

For testing you could apply: 'my-plugin-mock'