logic or ways to check if code logic performs as expected

Two Main Types:

• Unit Testing: testing of individual behaviors on different functional groups within an application (JUnit + Mockito)
• Integration Testing: testing correct overall functionality of multiple functional groups interacting within an application
• Accept Testing (UAT): verify the entire application including UI (Through UI)

  Why Testing

• Quality of Code: ensures existing logic is not broken by additional features as the application grows
• Documentation
• Test Driven Development: writing test cases before actual code, ensure the developer thinks thoroughly about business requirements and logic

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Perform testing

Testing Scenarios

• Happy Path Test: normal test cases
• Exception Path Test Case: programs handle faulty scenarios
• Edge Case: edge case

  Write deterministic test cases

  the test result should to change without a change in the code or test

  Test Naming Convention

• Package: Same as the source code
• Test Cases
  • GIVEN-WHEN-THEN structure
  • GIVEN: context of behavior
  • WHEN: the action that triggers it
  • THEN: the expected return

    Testing edge functions

• void return type
  • Checking input
  • Check exception
  • delete the shit
• private method (Through public methods)

  JUnit Module

• testing framework is widely used to perform unit testing on Java projects
• making sure to differentiate the JUnit 4 and JUnit 5
• Annotations
  • @ExtendWith: allow integration with additional modules
  • @Test: Marks a method as a test method for JUnit to execute
  • @DisplayName: Customize test case names in the report
  • @Disabled: Prevent execution of a test
• life cycle annotation
  • @BeforeAll: run before all test
  • @BeforeEach: run before each test
  • @AfterEach: run after each test
  • @AfterAll: run after all test

    Assertion

• Key to validate if the output from code is expected
• From JUnit 5, we cna use lambdas in assertion
• JUnit 5 also introduced assertAll() that allows us to group assertions and report any failed assertions with a MultipleFailuresError
• assertThrows: assert the Exception for the Exception Path Test Case
• assertEquals: utilize the equal func of the object
• assertSame: utilize the equal sign of the programming language

  Sprint Testing with JUnit

• Dependency injection
• when testing
  • Controller - Make/Mock an API call to a certain endpoint
  • Service - Test business logic
  • Repository - Test data-related operations
• Spring Testing specific annotation
  • @ExtendWith(SpringExtension.class)
    • Override several methods to process Unit Testing
  • @SpringBootTest
    • It creates ApplicationContext, which holds all the beans you need in the application
  • @AutoConfigureMockMvc
    • Start the mock servlet
  • @WebMvcTest
    • Only bootstrap the certain controller

      Mockito

      Achieving isolation which separating components to test them individually. We focus on testing one unit at a time

Mockito is used to mock interface so that dummy functionality can be added to mock interface that can be used in unit testing

• When testing the controller layer, we only want to focus on testing (fake object on real interface)

Mockito - Basic Annotations

• @Mock
  • It helps to create a Mock object, where we can stub/simulate the behavior of the object
  • It takes a Class as its parameters
• @Spy
  • It helps to create a Partial Mock object, where methods will be directly invoked unless those methods are stubbed
  • It takes an Instance as its parameter
• @InjectMocks
  • It injects mock fields into the object that needs to be tested automatically
  • It takes a Class as its parameter

Stubbing: Configure the mock and define what to do when specific methods of the mock are called

when(xxx.method()).thenReturn()
doReturn().when(xxx).method()
when().thenCallRealMethod()
when().thenThrow()

Verify

• Once a mock or spy has been used, we can verify that specific interactions took place
• syntax verify(mock, VerificationMode)

Testing in Repository

• verify our queries that retrieve, insert, update, and delete data
• call the database, but, without affecting the actual data
• Annotations
  • @DataJpaTest – load only the repository
  • @TestMethod(MethodOrder.OrderAnnotation.class) – Specify which test cases need to run first
  • @ActiveProfiles – Specif another profile that needs to be used during the test
  • @Order – On the method level, define the order of test cases
  • @Rollback – Spring will roll back all data changes

    Test Driven Development

    Code Coverage

• Code coverage is a software metric used to measure how many lines of our code are executed during automated tests
• JaCoco is a good tool to check the testing code coverage

  Test first

• create test case first
• developers create codes to meet test case requirements
• move to the next failed test case