Why @BeforeEach method in JUnit? - Purpose & Use Cases

The Big Idea

What if you could stop repeating setup steps and never worry about forgetting them again?

The Scenario

Imagine you have many tests for a calculator app. Before each test, you must set up the calculator with the same starting state manually. You open the app, clear previous data, and prepare it again and again for every single test.

The Problem

Doing this setup manually for each test is slow and boring. You might forget a step or do it differently each time. This causes tests to fail for the wrong reasons, making it hard to trust your results.

The Solution

The @BeforeEach method runs automatically before every test. It sets up the environment the same way every time, so you don't have to repeat code or worry about missing steps. This makes tests cleaner and more reliable.

Before vs After

✗ Before

void test1() {
  calculator.clear();
  // test code
}
void test2() {
  calculator.clear();
  // test code
}

✓ After

@BeforeEach
void setup() {
  calculator.clear();
}

@Test
void test1() {
  // test code
}

@Test
void test2() {
  // test code
}

What It Enables

It enables writing many tests quickly with confidence that each starts fresh and fair.

Real Life Example

Think of a chef preparing ingredients before cooking each dish. The @BeforeEach method is like prepping the kitchen so every recipe starts perfectly.

Key Takeaways

Repeats setup automatically before each test.

Prevents mistakes from manual setup.

Makes tests cleaner and easier to maintain.