How To Unit Test A POST REST Service Using Mockito With JUnit

In this blog of unit test, we will learn to post the request body to the specific POST mapping URL and in the response, we will check for HttpStatus and that the location header contains the URL of the created resource.

MockMvcRequestBuilders.post("/students/Student1/courses").accept(MediaType.APPLICATION_JSON):

Create a post request with an accept header for application\json

content(exampleCourseJson).contentType(MediaType.APPLICATION_JSON):

Use the specified content as body of the request and set content type header.

assertEquals(HttpStatus.CREATED.value(), response.getStatus()):

Assert that the return status is CREATED.

response.getHeader(HttpHeaders.LOCATION):

Get the location from response header and later assert that it contains the URI of the created resource.

Suppose we have a following POST Rest Service:

A successful resource creation by POST Service should return a status 201.

and we have the following service for Unit testing in which we have:

@PostMapping("/students/{studentId}/courses"):

A Mapping URL for the POST Request.

@RequestBody Course newCourse:

A Binding to bind the body of the request to Course object.

Executing a POST Rest Service

Example Request is shown below. It contains all the details to register a course to a student.

{
  "name": "Microservices",
  "description": "10 Steps",
  "steps": [
    "Learn How to Break Things Up",
    "Automate the hell out of everything",
    "Have fun"
  ]
}

The following example will show you how to apply Unit Test on above POST service:

@Test
public void createStudentCourse() throws Exception {
    Course mockCourse = new Course("1", "Smallest Number", "1",Arrays.asList("1", "2", "3", "4"));

    // studentService.addCourse to respond back with mockCourse
    Mockito.when(studentService.addCourse(Mockito.anyString(),Mockito.any(Course.class))).thenReturn(mockCourse);

    // Send course as body to /students/Student1/courses
    RequestBuilder requestBuilder = MockMvcRequestBuilders
            .post("/students/Student1/courses")
            .accept(MediaType.APPLICATION_JSON)
            .content(exampleCourseJson)
            .contentType(MediaType.APPLICATION_JSON);

    MvcResult result = mockMvc.perform(requestBuilder).andReturn();

    MockHttpServletResponse response = result.getResponse();

    assertEquals(HttpStatus.CREATED.value(), response.getStatus());

    assertEquals("http://localhost/students/Student1/courses/1",response.getHeader(HttpHeaders.LOCATION));
}