Generate JSON in Spring Boot tests

Joe Keen · October 16, 2022

spring

JacksonTester is a utility class included in the Spring Boot Test module to generate and parse JSON.

For example, to easily compare the response from a REST API with an object expectedStatus of type JobStatusDto.

@WebMvcTest(TransactionController.class)
@AutoConfigureJsonTesters
public class TransactionControllerTest {

    @MockBean
    private TransactionService transactionService;

    // This object will be initialised thanks to @AutoConfigureJsonTesters
    @Autowired
    private JacksonTester<JobStatusDto> jsonJobStatus;

    @Autowired
    private MockMvc mockMvc;

    @Test
    public void testGetJobStatus() throws Exception {
        // given
        long pJobId = 1L;
        JobStatusDto expectedStatus = new JobStatusDto(pJobId, "status", "message", "detailedMessage");
        given(transactionService.getJobStatus(pJobId)).willReturn(expectedStatus);

        // when
        MockHttpServletResponse response = mockMvc.perform(MockMvcRequestBuilders.get("/api/v1/job/1")).andReturn().getResponse();

        // then
        assertThat(response.getStatus()).isEqualTo(HttpStatus.OK.value());
        assertThat(response.getContentAsString())
                .isEqualTo(jsonJobStatus.write(expectedStatus).getJson());
    }
    
}