Testing Best Practices

Writing tests is only half the battle; maintaining them is often harder. Good tests follow the F.I.R.S.T. principles (Fast, Independent, Repeatable, Self-Validating, Timely) and avoid common anti-patterns like flakiness.

Structuring Tests: AAA Pattern

Tests should be structured using the Arrange, Act, Assert (AAA) pattern (or Given-When-Then in BDD):

• Arrange (Given): Initialize target objects and configure all dependencies.
• Act (When): Invoke the specific method or logic under test.
• Assert (Then): Verify the output, state, or mock interactions against expected invariants.

Code Walkthrough

This class demonstrates a cleanly structured unit test using the AAA pattern and clear naming.

import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.assertEquals;
class AccountTest {
@Test
    void deposit_ValidAmount_UpdatesBalanceCorrectly() {
        // Arrange (Given)
        Account account = new Account(100.00);
// Act (When)
        account.deposit(50.00);
// Assert (Then)
        assertEquals(150.00, account.getBalance(), "Deposit should increase balance");
    }
}

Interview-Relevant Information