passing static method as parameter in Java

Question

Hello I'm testing the class that has some validating methods and I've been wondering if there is a way to reduce the duplicated code.

@Test
void testCorrectEmailValidator() {
    List<String> correctEmails = Arrays.asList("[email protected]", "[email protected]", "[email protected]",
            "[email protected]", "[email protected]", "[email protected]");

    for (String email : correctEmails) {
        boolean isValid = UserCredentialsValidator.emailValidator(email);
        System.out.println("Email is valid: " + email + ": " + isValid);
        assertTrue(isValid);
    }
}

@Test
void testCorrectUsernameValidator() {
    List<String> correctUsernames = Arrays.asList("username", "123username", "username3", "user2name",
            "USERNAME", "USERNAME123", "123USERNAME123", "2uSERname33");

    for(String username : correctUsernames) {
        boolean isValid = UserCredentialsValidator.usernameValidation(username, userList);
        System.out.println("Username is valid:    " + username + "     : " + isValid);
        assertTrue(isValid);
    }
}

I also have validators for other fields such as username etc. I was thinking about implementing a helper method that would accept: tested credential as String, List but I've got a problem with last parameter - a validating method, not sure how to pass that.

The code i would like to replace with some method is the for loop.

Answer 1

I am afraid your tests are of low quality.

The problems that should be fixed immediately include

1. UserCredentialsValidator.usernameValidation(username, userList); The method shouldn't take the second argument. The place from where that list is retrieved should be concealed from the API consumer.

2. List<String> correctEmails = Arrays.asList(...) and List<String> correctUsernames = Arrays.asList(...) should be removed. You'd better make the tests parameterised with @ParameterizedTest and @ValueSource.

3. I'd rather remove the System.out.println statements. They make little sense in tests.

---

@ParameterizedTest
@ValueSource(strings = {"[email protected]", "[email protected]"})
void testUserEmailValidationWithValidUserEmailShouldPass(String validUserEmail) {
    boolean isValid = UserCredentialsValidator.emailValidator(validUserEmail);
    assertTrue(isValid);
}

@ParameterizedTest
@ValueSource(strings = {"username", "123username"})
void testUserNameValidationWithValidUserNameShouldPass(String validUserName) {
    boolean isValid = UserCredentialsValidator.usernameValidation(validUserName);
    assertTrue(isValid);
}

Now there is nothing to reduce.