Coding⏱️ 2 min read📅 2026-05-31

How to Fix: Mockito How to mock and assert a thrown exception?

Learn how to mock and assert a thrown exception with Mockito in JUnit tests.

Quick Answer: Use `when()` to throw an exception, then use `assertThrows()` or `verify()` to check the type of exception thrown.

📋 Table of Contents

  1. 🔍 Why This Happens
  2. 🛠️ Step-by-Step Verified Fixes
  3. 🎯 Final Words

Mockito is a popular mocking library for Java, and when it comes to testing exceptions, it can be a bit tricky. In this article, we'll explore how to mock and assert a thrown exception using Mockito in a JUnit test.

🔍 Why This Happens

  • When you're testing an exception, you want to ensure that the correct exception is thrown and caught. However, Mockito's default behavior is to not throw exceptions.

🛠️ Step-by-Step Verified Fixes

Method 1: Using Mockito's when() method with an exception

  1. Step 1: Use the `when()` method to specify that a certain method should throw an exception.

Method 2: Using Mockito's when() method with a custom exception

  1. Step 1: Create a custom exception that extends the `Exception` class.

🎯 Final Words

By following these steps, you can mock and assert a thrown exception using Mockito in your JUnit test. Remember to always verify that the correct exception is thrown and caught.

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