Unit Testing

Unit testing - Java, Play 2.4,2.5

Helpers and fakeApplication

Class Helpers is used a lot for unit tests. It imitates a Play application, fakes HTTP requests and responses, session, cookies - all whatever may be needed for tests. A controller under the test should be executed in a context of a Play application. The Helpers method fakeApplication provides an application for running tests. In order to use Helpers and fakeApplication a test class should derive from WithApplication.

The following Helpers API-s should be used:

Helpers.running(Application application, final Runnable block);
Helpers.fakeApplication();

Test with Helpers looks like this:

public class TestController extends WithApplication {
 @Test  
 public void testSomething() {  
     Helpers.running(Helpers.fakeApplication(), () -> {  
         // put test stuff  
         // put asserts  
     });
 }  
}

Adding import statements for Helpers methods makes code more compact:

 import static play.test.Helpers.fakeApplication;
 import static play.test.Helpers.running;
 ...
 @Test  
 public void testSomething() {  
      running(fakeApplication(), () -> {  
           // put test stuff  
           // put asserts  
       });
 }

}

Testing controllers

Let’s call a controller method, which is bound to the particular URL in the routes as a routed method. An invocation of a routed method is called a controller action and has a Java type Call. Play builds so-called reverse route to each action. Call to a reverse route creates an appropriate Call object. This reverse routing mechanism is used for testing controllers.

To invoke a controller action from test the following Helpers API should be used:

Result result = Helpers.route(Helpers.fakeRequest(Call action));

Controller tests example

The routes:

GET /conference/:confId controllers.ConferenceController.getConfId(confId: String)
POST /conference/:confId/participant controllers.ConferenceController.addParticipant(confId:String)

Generated reverse routes:

controllers.routes.ConferenceController.getConfId(conferenceId) 
controllers.routes.ConferenceController.addParticipant(conferenceId)

The method getConfId is bound to GET and does not receive a body in a request. It may be invoked for test with:

Result result = Helpers.route(Helpers.fakeRequest(controllers.routes.ConferenceController.getConfId(conferenceId)));

The method addParticipant is bound to POST. It expects to receive a body in a request. Its invocation in test should be done like this:

ParticipantDetails inputData = DataSimulator.createParticipantDetails();
Call action = controllers.routes.ConferenceController.addParticipant(conferenceId);
Result result = route(Helpers.fakeRequest(action).bodyJson(Json.toJson(inputData));

Mocking with PowerMock

To enable mocking a test class should be annotated as following:

@RunWith(PowerMockRunner.class)
@PowerMockIgnore({"javax.management.*", "javax.crypto.*"})
public class TestController extends WithApplication {
....

Mocking of a controller action

A controller call is mocked with RequestBuilder:

RequestBuilder fakeRequest = Helpers.fakeRequest(action);

For the above addParticipant an action is mocked with:

RequestBuilder mockActionRequest = Helpers.fakeRequest(controllers.routes.ConferenceController.addParticipant(conferenceId));

To invoke the controller method:

Result result = Helpers.route(mockActionRequest);

The whole test:

@Test
public void testLoginOK() {
 running(fakeApplication(), () -> {
      ///*whatever mocking*/Mockito.when(...).thenReturn(...);
      RequestBuilder mockActionRequest = Helpers.fakeRequest(
           controllers.routes.LoginController.loginAdmin());
      Result result = route(mockActionRequest);
      assertEquals(OK, result.status());
 });
}

Mocking of an action with JSON body

Let’s suppose, that an input is an object of type T. The action request mocking may be done in several ways.

Option 1:

public static <T> RequestBuilder fakeRequestWithJson(T input, String method, String url) {  
  JsonNode jsonNode = Json.toJson(input);  
  RequestBuilder fakeRequest = Helpers.fakeRequest(method, url).bodyJson(jsonNode);  
  System.out.println("Created fakeRequest="+fakeRequest +", body="+fakeRequest.body().asJson());  
  return fakeRequest;  
}

Option 2:

public static <T> RequestBuilder fakeActionRequestWithJson(Call action, T input) {  
  JsonNode jsonNode = Json.toJson(input);  
  RequestBuilder fakeRequest = Helpers.fakeRequest(action).bodyJson(jsonNode);  
  System.out.println("Created fakeRequest="+fakeRequest +", body="+fakeRequest.body().asJson());  
  return fakeRequest;  
}

Mocking of an action with Base authentication header

The action request mocking:

public static final String BASIC_AUTH_VALUE = "dummy@com.com:12345";
public static RequestBuilder fakeActionRequestWithBaseAuthHeader(Call action) {
  String encoded = Base64.getEncoder().encodeToString(BASIC_AUTH_VALUE.getBytes());
  RequestBuilder fakeRequest = Helpers.fakeRequest(action).header(Http.HeaderNames.AUTHORIZATION,
                                             "Basic " + encoded);
  System.out.println("Created fakeRequest="+fakeRequest.toString() );
  return fakeRequest;
}

Mocking of an action with session

The action request mocking:

public static final String FAKE_SESSION_ID = "12345";
public static RequestBuilder fakeActionRequestWithSession(Call action) {
  RequestBuilder fakeRequest = RequestBuilder fakeRequest = Helpers.fakeRequest(action).session("sessionId", FAKE_SESSION_ID);
  System.out.println("Created fakeRequest="+fakeRequest.toString() );
  return fakeRequest;
}

The Play Session class is just an extension of the HashMap<String, String>. It may be mocked with simple code:

public static Http.Session fakeSession() {  
  return new Http.Session(new HashMap<String, String>());  
}