Kotlin Language Features Related to Null Handling

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Any software engineer with a Java background would find the null handling features in the Kotlin language interesting. Let's summarize this topic with some examples. Nullable types: In Kotlin, types are non-nullable by default. If you want a variable to be able to hold a null value, you need to explicitly declare its type as nullable using the Type? syntax. For example, String? denotes a nullable string, while String represents a non-nullable string. Safe calls (?.): Kotlin introduces the safe call operator (?.) for handling nullable types. It allows you to safely invoke a method or access a property on a nullable object. If the object is null, the expression returns null instead of throwing a NullPointerException. Example: data class Person(val name: String, val age: Int, val address: String?) fun main() {     // Create a person with a nullable address     val person1 = Person("John Doe", 25, "123 Main Street")     val person2 = Person("Jane Doe", 30,...
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Mockist testler ve custom matcher yazımı

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Çalıştığım projede Mockito testlerini yoğun olarak kullanıyoruz ve birçok durumda custom matcher yazmamız sözkonusu oluyor.

Aşağıdaki mock test örneğine bakalım:

@Test
public void saveSkillAssignmentApprovalShouldCreateNew() throws ServiceException {
Skill skill = new SkillBuilder().buildSample();
SkillAssignmentDao dao = mock(SkillAssingmentDao.class);
//...


// manager kendi icerisinde dao.save(..) metodunu cagiriyor.
SkillAssignment result = skillAssignmentManager.saveSkillAssignmentApproval(approver, skill, skillLevel);

// burada assertion icin result'i kullanamayiz cunku mock dao tarafindan set //ediliyor.
assertThat(result.getSkill(),equalTo(skill)); // ??
}

Burada test ettiğimiz skillAssignmentManager nesnesinin geri gönüş değeri yoluyla sınama yapamayacağımız açık. O nedenle mock olarak kullandığımız dao metoduna geçilen parametreyi sınamamız gerekiyor:

@Test
public void saveSkillAssignmentApprovalShouldCreateNew() throws ServiceException {
SkillAssignmentDao skillAssignmentDao = mock(SkillAssingmentDao.class);
//...


// manager kendi icerisinde dao.save(..) metodunu cagiriyor.
skillAssignmentManager.saveSkillAssignmentApproval(approver, skill, skillLevel);

IsExpectedAssignment isExpectedAssignment = new IsExpectedAssignment( skill);

verify(skillAssignmentDao).save(argThat(isExpectedAssignment));

}

class IsExpectedAssignment extends ArgumentMatcher {
private Skill skill;

public IsExpectedAssignment(Skill skill) {
this.skill = skill;
}

public boolean matches(Object skillAssignment) {
SkillAssignment actual = (SkillAssignment) skillAssignment;

if (!actual.getSkill.equals(skill))
return false;

//...
}

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