Retromock

like Wiremock for Retrofit, but faster.

What is it?

Retromock is an easy way to mock external APIs if you use Square's HTTP client, retrofit. It allows you to specify expected requests and corresponding responses using a DSL reminiscent of wiremock.

Request matching is performed with hamcrest matchers, so it is easy to extend the DSL with your own matchers, e.g. for custom authentication schemes. Retromock comes with a wide variety of matchers that allow you to match on many parts of an HTTP request, including the path, query parameters or headers. You can also use JSON Path expressions to match on POST or PUT request bodies.

How do I use Retromock?

tl;dr: look at MockClientTest.

To use Retormock, you perform these steps:

1. use the DSL to setup routes

   MockClient.Provider mockClient = MockClient.when()
    .GET("/some/path")
    .withHeader("x-foo", is("headerVal"))
    .matching(body(
      jsonPath("title", startsWith("test")),
      jsonPath("properties.foo", is(200))
    ))
    .thenReturn(helloWorld);

many of the methods are overloaded or have alternative ways of specifying the same functionality. For example, if you want to specify the request method yourself, you can use MockClient.when().aRequest().withMethod("PATCH").andPath("/whatever").

1. Tell Retrofit to use your mock client instead of the HTTP client library you usually use

   RestAdapter restAdapter = new RestAdapter.Builder()
      .setClient(mockClient)
      .setEndpoint("http://example.org/") // ignored, but you must set some value
      // more config, e.g. for request interceptors
      .build();

2. Use Retrofit as usual

   YourApiClient yac = restAdapter.create(YourApiClient.class);
   
   assertEquals("Hello, World", yac.someMethod());

Alternatives to Retromock

Depending of how much "infrastructure" you want to test, there are other approaches you can use.

• In the simplest case, if you use retrofit, your API clients are simple Java interfaces, so you can provide mock implementations of the interfaces or use a mocking library like Mockito.

• If you want to simulate network conditions like delays / connection failures, Square provides retrofit-mock.

• Or you can go the whole hog and ramp up a server to serve your mock responses with various libraries like wiremock, et al.