Test fixtures and lifecycle in Kotlin - Step-by-Step Execution

Concept Flow - Test fixtures and lifecycle

Start Test Class

↓

BeforeAll: Setup shared resources

↓

For each Test Method

↓

BeforeEach: Setup test fixture

↓

Run Test Method

↓

AfterEach: Cleanup test fixture

↓

Repeat for next Test Method

↓

AfterAll: Cleanup shared resources

↓

End Test Class

This flow shows how test fixtures are set up and cleaned up before and after tests run in a Kotlin test class.

Execution Sample

Kotlin

import org.junit.jupiter.api.*

@TestInstance(TestInstance.Lifecycle.PER_CLASS)
class CalculatorTest {
    @BeforeAll
    fun setupAll() { println("Setup All") }

    @BeforeEach
    fun setup() { println("Setup Each") }

    @Test
    fun testAdd() { println("Test Add") }

    @AfterEach
    fun tearDown() { println("Tear Down Each") }

    @AfterAll
    fun tearDownAll() { println("Tear Down All") }
}

This code runs setup and teardown methods around each test and once for all tests.

Execution Table

Step	Annotation	Action	Output
1	@BeforeAll	Run once before all tests	Setup All
2	@BeforeEach	Run before testAdd	Setup Each
3	@Test	Run testAdd method	Test Add
4	@AfterEach	Run after testAdd	Tear Down Each
5	@AfterAll	Run once after all tests	Tear Down All
6	End	All tests finished	No more output

💡 All test lifecycle methods have run, tests complete.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	After Step 5	Final
Test Class State	Not started	Setup All done	Setup Each done	Test Add done	Tear Down Each done	Tear Down All done	Finished

Key Moments - 3 Insights

Why does @BeforeAll run only once but @BeforeEach runs before every test?

@BeforeAll is for shared setup before any tests run (see Step 1), while @BeforeEach prepares the environment fresh for each test (see Step 2).

What happens if there are multiple test methods?

The @BeforeEach and @AfterEach methods run before and after each test method, repeating steps 2-4 for each test.

When does @AfterAll run?

@AfterAll runs once after all tests and their fixtures finish (see Step 5).

Visual Quiz - 3 Questions

Look at the execution table, what is printed at Step 3?

A Test Add

B Setup Each

C Tear Down Each

D Setup All

💡 Hint

Check the 'Output' column for Step 3 in the execution_table.

At which step does the shared setup for all tests happen?

A Step 2

B Step 1

C Step 4

D Step 5

💡 Hint

Look for @BeforeAll annotation in the execution_table.

If a second test method is added, which lifecycle methods run again before it?

A @BeforeAll only

B @AfterAll only

C @BeforeEach and @AfterEach

D No lifecycle methods run again

💡 Hint

Refer to key_moments about multiple test methods and steps 2-4 in execution_table.

Concept Snapshot

Test fixtures in Kotlin use annotations:
@BeforeAll runs once before all tests
@BeforeEach runs before each test
@Test marks test methods
@AfterEach runs after each test
@AfterAll runs once after all tests
This manages setup and cleanup cleanly.

Full Transcript

This visual trace shows how Kotlin test fixtures and lifecycle annotations work. First, @BeforeAll runs once to set up shared resources. Then for each test method, @BeforeEach runs to prepare the test environment, followed by the test method itself marked with @Test. After the test, @AfterEach cleans up. After all tests finish, @AfterAll runs once to clean up shared resources. The execution table shows the order and output of these steps. Variables track the test class state changing from not started to finished. Key moments clarify why some methods run once and others multiple times. The quiz tests understanding of the lifecycle order and method roles.