Snippet

Unit Testing Outbound API Clients with MockRestServiceServer

@RestClientTest focuses testing solely on RestTemplate or RestClient builders by mocking external HTTP endpoints via MockRestServiceServer. It asserts correct URL construction, header propagation, and payload deserialization without opening real network sockets.

snippet.java

java

@RestClientTest(GithubClient.class)
class GithubClientTest {
    @Autowired
    private GithubClient githubClient;
 
    @Autowired
    private MockRestServiceServer server;
 
    @Test
    void fetchesUserRepositories() {
        this.server.expect(requestTo("/users/octocat/repos"))
            .andRespond(withSuccess("[{\"name\":\"repo1\"}]", MediaType.APPLICATION_JSON));
 
        List<RepositoryDto> repos = githubClient.getRepositories("octocat");
 
        assertThat(repos).hasSize(1);
    }
}

spring

Breakdown

@RestClientTest(GithubClient.class)

Prepares an isolated test slice specifically for the specified REST client bean.

this.server.expect(requestTo("/users/octocat/repos"))

Declares expectations for the outbound HTTP request URI.

.andRespond(withSuccess(...))

Mocks an HTTP 200 response with custom payload and media type headers.

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Unit Testing Outbound API Clients with MockRestServiceServer

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