JUnit 5 from Basics to Advanced

Unit Testing in Java

What you’ll learn
Unit Testing
JUnit5
Mockito
Java Testing Framework

Requirements
Java

Description
Unit testing roadmap

Topics already covered

– Available Frameworks

– Junit

– TestNG etc.

– What is a unit test?

– Difference between unit vs integration vs functional tests

– AAA (Arrange-Act-Assert)

– Maven/Gradle dependencies

– Test Lifecycle

– Basic Annotations

• @Test

• @BeforeEach, @AfterEach

• @BeforeAll, @AfterAll

• @DisplayName

• @Disable

etc.

– Assertions

• assertEquals, assertNotEquals

• assertTrue, assertFalse

• assertNull, assertNotNull

• assertThrows for exception testing

– Extensions

– Test Repetition

• @RepeatedTest(n)

Upcoming

– Parameterized Tests

Mocking

– Available Frameworks

– Mockito

– EasyMock

– JMock

– Mockito Core Concepts

• @Mock and Mockito.mock(Class.class)

• @InjectMocks for injecting mocks

• @BeforeEach with MockitoAnnotations.openMocks(this)

• Testing Private/Static Methods (PowerMock or some other approach)

– Stubbing Behavior

• when(…).thenReturn(…)

• when(…).thenThrow(…)

– Verifying Calls

• verify(…) after method call

• verifyNoMoreInteractions(…)

– Void Method Stubbing

• doNothing().when(mock).method()

• doThrow(…).when(…)

– Argument Matchers

• any(), eq(), anyString(), anyInt(), etc.

• Mixing matchers with exact values (and why it fails)

– Behavior Verification

– Verify how many times called: times(n), never(), atLeastOnce()

– Spies vs Mocks

○ Mockito.spy() for partial mocking

○ Difference between mock() and spy()

– Testing Configuration, Properties, and Profiles

– Unit tests with different Spring profiles.

– How to mock @Value, Environment, or @ConfigurationProperties.

– Overriding properties for test-only behavior.

Assertions & Matchers

– Frameworks

– AssertJ

– Hamcrest

Some Advanced Topics

– Test-Driven Development (TDD)

– Write failing test first, then code

– Test Coverage

• Tools: JaCoCo, IntelliJ coverage tool

– CI integration

– Run tests in GitHub Actions, GitLab CI/CD, Jenkins.

– Test Reports

– Generate HTML/XML test reports for build tools.

AI + Unit Testing

– Code Suggestion Tools (AI-Powered IDE Extensions)

– Using AI in CI/CD (Future-Forward)

– AI suggests missing test cases for changed methods

– AI flags flaky or redundant tests

– Autogenerate Missing Tests

Who this course is for
Java Backend Developers

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