[FIXED] How to mock my service using Mockito framework

Issue

Hello I have struglling write a mock test according to my following method below;

my code below;

@Component
public class CodeConfigBuilder {

    @Value("${promoConfig.prefix.length}")
    private Integer prefixLength;

    public void validateRequestAndSetDefaults(PromoRequest promoRequest) {
        prefixAndPostFixControlAccordingToLength(promoRequest);
    }

    private void prefixAndPostFixControlAccordingToLength(PromoRequest promoRequest) {
        if (promoRequest.getPostfix() != null) {
            int lengthControl = prefixLength + promoRequest.getPostfix().length();
            if (lengthControl >= promoRequest.getLength()) {
                throw new BadRequestException(Constant.ClientConstants.THE_SUM_OF_PREFIX_AND_POSTFIX_CAN_NOT_BE_GREATER_THAN_LENGHT);
            }
        }    
    }
}

my yml configuration below;

 #=========  Promo  Config  ========== #
    
        promoConfig:
          prefix:
            length: 3

my service below;

public void validateRequest(PromoRequest promoRequest) {
      
        codeConfigBuilder.validateRequestAndSetDefaults(promoRequest);
    }

I have a created PropertySourceResolver class

@Component
@Getter
public class PropertySourceResolver {
private int prefixLength = 3;

and my test class below;

@RunWith(MockitoJUnitRunner.class)
class CodeConfigBuilderTest {

   @MockBean
    private PropertySourceResolver propertySourceResolver = new PropertySourceResolver();
    @InjectMocks
    private PromoRequest promoRequest = new PromoRequest();
    @InjectMocks
    private PromoService Service;

   @Before
    public void init() {

        promoRequest.setPrefix("ABC");
        promoRequest.setPostfix("ABCDABCD");
        promoRequest.setQuantity(10);
        promoRequest.setLength(12);
        promoRequest.setCharset("ABCDEF");
    }

    @Test
    public void prefixAndPostFixControl_accordingToLength_for_Succeed() {

        int lengthControl = promoRequest.getPrefix().length() + promoRequest.getPostfix().length();

        if (lengthControl >= promoRequest.getLength()) {
            Assert.assertTrue(false);
        }
    }

I like to change my code according to test scenarios like ; when ... then return any idea? thank you.

Solution

To make this simpler and better organize your code, abstract away the complexity of injecting the configurations by creating the following class:

@ConfigurationProperties(prefix = "promoConfig.prefix")
public class PromoPrefixConfiguration {
    private Integer length;

    public Integer getLength() {
        return length;
    }
}

Then, you should make this a dependency for CodeConfigBuilder:

@Component
public class CodeConfigBuilder {

    private Integer prefixLength;

    public CodeConfigBuilder(PromoPrefixConfiguration promoPrefixConfiguration) {
        this.prefixLength = promoPrefixConfiguration.getLength();
    }

    public void validateRequestAndSetDefaults(PromoRequest promoRequest) {
        prefixAndPostFixControlAccordingToLength(promoRequest);
    }

    private void prefixAndPostFixControlAccordingToLength(PromoRequest promoRequest) {
        if (promoRequest.getPostfix() != null) {
            int lengthControl = prefixLength + promoRequest.getPostfix().length();
            if (lengthControl >= promoRequest.getLength()) {
                throw new BadRequestException(Constant.ClientConstants.THE_SUM_OF_PREFIX_AND_POSTFIX_CAN_NOT_BE_GREATER_THAN_LENGHT);
            }
        }    
    }
}

Now, in order to test this class you have to do it with three tests:

1. Test that PromoRequest is valid because postfix is null;
2. Test that PromoRequest is valid because length is valid;
3. Test that PromoRequest is invalid because length is not valid;

They would be something like the following:

class CodeConfigBuilderTest {

    private PromoPrefixConfiguration promoPrefixConfiguration = new PromoPrefixConfiguration(10);
    private CodeConfigBuilder codeConfigBuilder = new CodeConfigBuilder(promoPrefixConfiguration);

    @Test
    public void promoRequestIsValidGivenNullPostfix() {
        // Arrange
        PromoRequest promoRequest = new PromoRequest();
        promoRequest.setPostfix(null);

        // Act
        codeConfigBuilder.validateRequestAndSetDefaults(promoRequest);
    }

    @Test
    public void promoRequestIsValidGivenValidPrefixPlusPostfixLength() {
        // Arrange
        PromoRequest promoRequest = new PromoRequest();
        promoRequest.setPostfix("ABCD");
        promoRequest.setLength(15);

        // Act
        codeConfigBuilder.validateRequestAndSetDefaults(promoRequest);
    }

    @Test(expected = BadRequestException.class)
    public void promoRequestIsInvalidGivenInvalidPrefixPlusPostfixLength() {
        // Arrange
        PromoRequest promoRequest = new PromoRequest();
        promoRequest.setPostfix("ABCDEFGH");
        promoRequest.setLength(15);

        // Act
        codeConfigBuilder.validateRequestAndSetDefaults(promoRequest);
    }
}

If you are using JUnit 5, you could replace the last test with the following one to easily assert the exception message:

@Test
public void promoRequestIsInvalidGivenInvalidPrefixPlusPostfixLength() {
    // Arrange
    PromoRequest promoRequest = new PromoRequest();
    promoRequest.setPrefix("ABCDEFG");
    promoRequest.setPostfix("HIJKLMN");

    // Act 
    Exception exception = assertThrows(BadRequestException.class, () -> {
        codeConfigBuilder.validateRequestAndSetDefaults(promoRequest);
    });

    // Assert
    String exceptionMessage = exception.getMessage();
    assertTrue(exceptionMessage.equals(Constant.ClientConstants.THE_SUM_OF_PREFIX_AND_POSTFIX_CAN_NOT_BE_GREATER_THAN_LENGHT));
}

P.S.: do you mean suffix instead of postfix?

Answered By - João Dias
Answer Checked By - Candace Johnson (JavaFixing Volunteer)