assertTrue and assertFalse in JUnit - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the JUnit method assertTrue(condition) check?

It checks that the given condition is true. If the condition is false, the test fails.

beginner

What happens when assertFalse(condition) is used and the condition is true?

The test fails because assertFalse expects the condition to be false.

beginner

How would you use assertTrue to check if a number is positive?

Use assertTrue(number > 0). This passes if the number is greater than zero.

beginner

Why is it important to use assertTrue and assertFalse in tests?

They help confirm that conditions in your code behave as expected, catching errors early.

intermediate

Can assertTrue and assertFalse include a message? How?

Yes. You can add a message as the first argument, like assertTrue("Must be true", condition). This message shows if the test fails.

What does assertTrue(condition) do in a JUnit test?

A Always passes the test

B Fails the test if condition is false

C Passes the test if condition is false

D Throws an exception regardless of condition

assertTrue expects the condition to be true. If it is false, the test fails.

Which method would you use to check that a condition is false?

A assertFalse

B assertNull

C assertEquals

D assertTrue

assertFalse checks that the condition is false.

What happens if assertFalse(condition) receives a true condition?

A Test is skipped

B Test passes

C Test fails

D Test throws an error

The test fails because assertFalse expects false.

How can you add a custom failure message to assertTrue?

A assertTrue(condition, message)

B assertTrue()

C assertTrue(condition)

D assertTrue(message, condition)

The message comes first: assertTrue("message", condition).

Which of these is a good use of assertTrue?

A assertTrue(user.isLoggedIn())

B assertTrue(user == null)

C assertTrue(false)

D assertTrue(5 < 3)

Checking if a user is logged in returns true or false, so assertTrue(user.isLoggedIn()) is valid.

Explain how assertTrue and assertFalse help in writing tests.

Think about what happens when conditions are not met.

Write a simple example using assertTrue to check if a number is even.

Even numbers have zero remainder when divided by 2.