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In JUnit tests, you usually compare objects with assertions, not with ==. The most common choices are: assertEquals(expected, actual) — compares objects using their equals() method. assertSame(expected, actual) — checks whether both references point to the same object. AssertJ’s assertThat(actual).isEqualTo(expected) — a more fluent alternative. Field-by-field assertions — useful when you only care about some […]
You can use AssertJ with JUnit to write more readable, fluent assertions than standard JUnit assertions. 1. Add AssertJ Dependency If you use Maven: <dependency> <groupId>org.assertj</groupId> <artifactId>assertj-core</artifactId> <version>3.26.3</version> <scope>test</scope> </dependency> If you use Gradle: testImplementation("org.assertj:assertj-core:3.26.3") 2. Use AssertJ in a JUnit Test Import assertThat statically: import org.junit.jupiter.api.Test; import static org.as...
You can test repository-like classes without a real database by replacing the database dependency with a fake, mock, or in-memory implementation, depending on what you want to verify. 1. Use mocks for unit tests If your class depends on a repository interface, mock it and verify behavior without touching a database. Example with JUnit 5 […]
Testing Service Classes with JUnit and Mockito Service classes are usually where your business logic lives. They often depend on repositories, clients, mappers, validators, or other services. When unit testing a service, the goal is usually: test the service logic itself mock external dependencies avoid starting the Spring container unless necessary verify returned values, exceptions, […]
In JUnit tests, you usually don’t “mock” exceptions directly. Instead, you either: Assert that real code throws an exception, or Configure a mock dependency to throw an exception. 1. Assert that code throws an exception With JUnit 5, use assertThrows. import org.junit.jupiter.api.Test; import static org.junit.jupiter.api.Assertions.assertEquals; import static org.junit.jupiter.api.Assertions.assertThrows; class MyServiceTest { @Test void shouldThrowException() { […]
To verify method calls with Mockito and JUnit, use Mockito’s verify() method. This lets you check whether a mocked dependency method was called, how many times it was called, and what arguments were passed. 1. Basic Example Suppose you have a service that depends on a repository. public interface UserRepository { void save(User user); } […]
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