Tag Archives: Mockito

Mock nested method calls using Mockito in Spring Boot

Posted by on November 27, 2020 No comments

Quite often you have a nested call chain to get a result in Java. Mocking these in a test is a little different than mocking just one call. I’m here going to show a solution to that.

Say you have the following call chain to create a transacted session for a JMS connection:

Session session = 
           connectionFactory.createConnection()
                            .createSession(Session.SESSION_TRANSACTED);

To mock these calls we have to break them apart and mock them one by one

    
...
public MyTestClass {
  @Mock
  private Session session;

  @Mock
  private ConnectionFactory connectionFactory;

  @Mock
  private Connection mockedConnection;

  @BeforeMethod
  public void setUp() throws JMSException {
    MockitoAnnotations.initMocks(this);
    Mockito.when(connectionFactory.createConnection())
                                          .thenReturn(mockedConnection);
    Mockito.when(mockedConnection.createSession(
                                           Session.SESSION_TRANSACTED))
                                          .thenReturn(session);
  }
...

We are now ready to create all our tests 🙂

Tested on Java v1.8.0_252, Mockito v3.3.3, Spring Boot v2.2.4 and TestNG v6.11

Mock a dependency in system under test in a Spring Boot application with Mockito

Posted by on November 9, 2020 No comments

System under test class example:

import my.special.sclient
...

class App {
  Sclient sclient = getNewSclient();
  
  public String methodA(String input) { 
    return sclient.getValue(input);
  }

  protected Sclient getNewSclient() {
    return new Sclient();
  }
}

Test class example:

import org.mockito.InjectMocks;
import org.mockito.Spy;
import org.mockito.Mock;
import org.mockito.MockitoAnnotations;

import org.testng.annotations.BeforeMethod;
import org.testng.annotations.Test;
...

class Test {
  @Spy
  @InjectMocks
  private App sut;

  @Mock
  Sclient mockClient;

  @BeforeMethod
  public void setUp() {
    MockitoAnnotations.initMocks(this);
    when(sut.getNewSclient()).thenReturn(mockClient);
    when(mockClient.getValue("bar")).thenReturn("foo");
  }

  @Test
  public void myTest() {
    String value = sut.getValue("bar");
    assertThat(value, is("foo"));
  }
}

So, how does this work? I will try to explain below:

1. First we need to be able to intercept the ‘sclient’ in the App class. This is done by simply creating a ‘getNewSclient()’ function and then mock it in the Test class so that we instead can use a mocked version of it.

2. Next we need to setup our test class. Here we need both a @Spy and @InjectMocks on the App object. We also need a mocked instance of the ‘sclient’ we are going to use

3. Now we need to set upp the desired behaviour of our mocked ‘sclient’. We set it so that if you input “bar” you should get “foo” back

4. Done!

Tested on Java v1.8.0_252, Mockito v3.3.3, TestNG v6.11 and Spring Boot v2.2.4