Testing no exception thrown in JUnit - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does it mean to test that no exception is thrown in JUnit?

It means verifying that a piece of code runs without causing any errors or exceptions. The test passes if no exceptions occur during execution.

beginner

How do you write a JUnit test to check that no exception is thrown?

Simply write the test method to call the code. If the code runs without throwing exceptions, the test passes. No special annotation is needed for this.

beginner

Why is it important to test that no exception is thrown?

Because it confirms the code behaves as expected under normal conditions and does not crash or fail unexpectedly.

beginner

What happens if an exception is thrown during a JUnit test that expects no exception?

The test fails immediately, showing the exception details in the test report.

intermediate

Can you use assertDoesNotThrow in JUnit 5 to test no exception is thrown? How?

Yes. Use assertDoesNotThrow(() -> { code }); to explicitly check no exception is thrown. It improves test clarity.

In JUnit, what happens if your test method throws an unexpected exception?

A The test retries automatically

B The test fails

C The test is ignored

D The test passes

If an unexpected exception is thrown, JUnit marks the test as failed.

Which JUnit 5 method explicitly checks that no exception is thrown?

A assertThrows

B assertEquals

C assertDoesNotThrow

D assertNull

assertDoesNotThrow verifies that the code block runs without throwing exceptions.

If you want to test that a method runs without exceptions, what is the simplest approach?

A Just call the method in the test without extra code

B Wrap the call in try-catch and fail on catch

C Use assertThrows with no exception

D Use fail() method

Simply calling the method is enough; if an exception occurs, the test fails automatically.

Why might you prefer assertDoesNotThrow over just calling the method in a test?

A It ignores exceptions

B It catches exceptions silently

C It slows down the test

D It makes the test intention clearer

assertDoesNotThrow clearly shows the test expects no exceptions, improving readability.

What tag would you use to mark a test that verifies no exceptions are thrown?

A @Test

B @Test(timeout=1000)

C @Test(expected=Exception.class)

D @Ignore

Just @Test is used; no special annotation is needed to test no exceptions.

Explain how to write a JUnit test that verifies no exception is thrown when running a method.

Think about what happens if an exception is thrown during a test.

Describe the difference between using assertDoesNotThrow and just calling the method in a JUnit test.

Consider clarity and intention in tests.