assertDoesNotThrow in JUnit - Build an Automation Script

Verify that a method does not throw any exception

Preconditions (2)

Step 1: Call the 'calculate' method with inputs 10 and 2

Step 2: Verify that no exception is thrown during the method call

✅ Expected Result: The 'calculate' method completes without throwing any exception

Automation Requirements - JUnit 5

Assertions Needed:

Use assertDoesNotThrow to verify no exception is thrown when calling calculate(10, 2)

Best Practices:

Use lambda expression inside assertDoesNotThrow for the method call

Keep test method names descriptive and clear

Avoid catching exceptions manually inside the test

Automated Solution

JUnit

import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
import org.junit.jupiter.api.Test;

public class CalculatorTest {

    // Method to test
    public int calculate(int a, int b) {
        return a / b;
    }

    @Test
    public void testCalculateDoesNotThrow() {
        assertDoesNotThrow(() -> {
            int result = calculate(10, 2);
        });
    }
}

This test class defines a method calculate that divides two integers.

The test method testCalculateDoesNotThrow uses assertDoesNotThrow from JUnit 5 to check that calling calculate(10, 2) does not throw any exception.

The method call is wrapped inside a lambda expression passed to assertDoesNotThrow. This is the recommended way to verify that no exception occurs during execution.

We do not catch exceptions manually because assertDoesNotThrow handles that and fails the test if an exception is thrown.

Common Mistakes - 3 Pitfalls

Catching exceptions manually inside the test instead of using assertDoesNotThrow

Passing the method call result directly to assertDoesNotThrow instead of a lambda

Using assertDoesNotThrow for methods that should throw exceptions

Bonus Challenge

Now add data-driven testing with 3 different input pairs to verify calculate does not throw exceptions

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