Nowadays, most Unit tests are written following the BDD style (Given, When, Then) and use JUnit, Mockito framework and
AssertJ assertions, which is shown in section 1.
In section 2, we show how BDDMockito can help to write more readable tests replacing Mockito.when keyword by
BDDMockito.given in the "Given" section.
Section 3 improves the code of section 2 using BDDAssertions.then assertions from AssertJ.
Only Mockito.when keyword is used, but it is used in the "Given" section, which is puzzling :-(
@Test
public void retrieveUsersShouldReturnExistingUsersWhenUsersArePresent() {
// Given
var user1 = Mockito.mock(User.class);
var user2 = Mockito.mock(User.class);
Mockito.when(userRepository.retrieveUsers()).thenReturn(of(user1, user2));
// When
var retrievedUsers = userService.retrieveUsers();
// Then
Assertions.assertThat(retrievedUsers).containsExactlyInAnyOrder(user1, user2);
}
See source code
Mockito.when calls have been replaced by BDDMockito.given ones in the "Given" section, which makes more sense and is easier to read :-)
@Test
public void retrieveUsersShouldReturnExistingUsersWhenUsersArePresent() {
// Given
var user1 = Mockito.mock(User.class);
var user2 = Mockito.mock(User.class);
BDDMockito.given(userRepository.retrieveUsers()).willReturn(of(user1, user2));
// When
var retrievedUsers = userService.retrieveUsers();
// Then
Assertions.assertThat(retrievedUsers).containsExactlyInAnyOrder(user1, user2);
}
See source code
3. Even more readable tests using BDDMockito.given, Assertions.assertThat and BDDAssertions.then from AssertJ
"Then" sections uses BDDAssertions.then assertions.
Our test now fully complies with BDD style, except of course the lack of when keyword (which is implicit) in the
"When" section.
@Test
public void retrieveUsersShouldReturnExistingUsersWhenUsersArePresent() {
// Given
var user1 = Mockito.mock(User.class);
var user2 = Mockito.mock(User.class);
BDDMockito.given(userRepository.retrieveUsers()).willReturn(of(user1, user2));
// When
var retrievedUsers = userService.retrieveUsers();
// Then
BDDAssertions.then(retrievedUsers)
.as("Should have returned the list of users")
.containsExactlyInAnyOrder(user1, user2);
}
See source code
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