Using Mockito for API Stubbing Load Test

Question

I have a Spring Boot application with a REST API. Behind the scenes it uses a vended SDK to call the vendors service. I need to run load tests on my application, but don't want to call the vendor API and accidentally crash their system during testing.

Is it possible to use Mockito outside of a JUnit test to create a mock for the vendor SDK objects during the normal application runtime?

I figured I would use a profile based configuration beam to enable the mocked object when profile is “performance-test”. But I can find no article/discussion/mention of anyone using Mockito this way and it is making me second guess my approach. Thoughts?

Answer 1

You probably should look for using wiremock or similar software to mock the vendor service, like here: Integration Testing with a fake server

Wiremock is a stub server that you can conveniently start/stop from within JUnit tests. It acts like the remote server when you set up responses. The documentation is really good, I do not want to copy&paste all of it here.

Just a sample:

public class MyTest {
    @Rule
    public WireMockRule wireMockRule = new WireMockRule(wireMockConfig().dynamicPort().dynamicHttpsPort());

    @Test
    public void exampleTest() {
        stubFor(get(urlEqualTo("/my/resource"))
                .willReturn(aResponse()
                    .withStatus(200)
                    .withBody("<response>Some content</response>")));

        ...        
        verify(postRequestedFor(urlMatching("/my/resource/[a-z0-9]+"))
                .withRequestBody(matching(".*<message>1234</message>.*")));
    }
}

For loadtest, you would rather run the stub standalone somewhere, and have some script set up the responses.

You probably don't find mention of Mockito because embedding mocks with stub responses into your application is a bad idea and will not help you getting realistic results for load tests (because your responses will be much faster and not pass through serialization/deserialization).

Else also look here: How to mock remote REST API in unit test with Spring?