Mockito exception handling example Mockito To mock and assert a thrown exception in Mockito, you can use the doThrow() method and the verify() method. verify(); We can use only one method to verify exceptions. How to throw an exception on a void method in Mockito? To throw an exception on a void method in Mockito, you can use the `doThrow()` method. Dec 26, 2023 · 3. N. The doThrow() method in Mockito is used to specify that a method call on a mock object should throw an exception. getMessage(). expectNextCount(4) . ui. demo; import org. InjectMocks; import static org. You can use assertThrows(), But with assertThrows your assertion will pass even if the thrown exception is of child type. Dependencies and Technologies Used: mockito-core 3. When writing unit tests, we need to ensure that our code handles exceptions correctly. Solutions. Mar 26, 2025 · Now, after four all elements, we expect our stream to terminate with an exception: StepVerifier . 3: Mockito mock objects library core API and implementation. Model; import java. mockito. ), Class. Mockito makes it easy to configure a mock object to throw an exception when a specific method is called. ” Mockito Framework Site. The `doThrow()` method takes a `Throwable` object as an argument. assertNull; import static org. Spring Boot MockMvc for rest controller endpoints. Web. Mock; import org. println("blam"); } } @Component @RequiredArgsConstructor public class Kapow { private final Blam blam; public void aMethod() { blam. In this detailed guide, we'll explore each of these approaches with multiple examples. p. This is because, JUnit 5 checks exception type by calling Class. Guides on Java Exception Handling Concepts. Dedicated local streams across North America, Europe, and Asia-Pacific will explore the latest Java AI models to develop LLM apps and agents, learning best practices for app modernization with AI-assisted dev tools, learning the latest in Java frameworks Mar 1, 2013 · I have a method with a void return type. expectErrorMatches(throwable -> throwable instanceof IllegalArgumentException && throwable. Stubbing Multiple Calls. Utilize `doThrow()` in Mockito to specify that a mock should throw an exception when a specified method is called. Mocking Checked Exceptions. The workaround for this is to assert on Class: Jan 8, 2024 · Connect with experts from the Java community, Microsoft, and partners to “Code the Future with AI” JDConf 2025, on April 9 - 10. Before; import org. io To test this method using Mockito, you would need to do the following: Create a test method that uses the JUnit @Test annotation. 28 Apr. Use Mockito to create mock objects and PowerMock to handle static methods offer enhanced capabilities for unit tests. Feb 1, 2025 · Scenario: Mocking a Service to Throw an Exception for Testing Error Handling in a Controller 1. Learn how to handle exceptions and mock retry logic using Mockito in Java. Verifying Exception Handling: You can verify that your code handles exceptions properly using Learn how to handle exceptions effectively in Mockito with examples and best practices for robust testing. File: CalculatorService. This test will fail with the message in the console. MockitoAnnotations; import org. Tagged with java, mockito, junit, springboot. 3. 2017. 13: JUnit is a unit testing framework for Java, created by Erich Gamma and Kent Beck. isInstance(. Before we begin mocking exceptions with Mockito, it’s important to ensure we have a clear understanding of the necessary Mockito concepts. Matches Specified Exception or Its Child Exception. Jan 18, 2025 · 1. Mockito. Simulating API Failures with Mockito: A Complete Guide Introduction. Test; import org. — “Mockito. package com. Writing unit test cases for spring boot controllers. For example, let's say we have a method that reads from a file and throws a FileNotFoundException if the file does not exist. 2. Jan 26, 2019 · In this tutorials, we are going to write JUnit test cases for Spring Boot controller. 3. java. Check out the complete Java tutorial at Java Tutorial | Learn Java Programming with Examples. Mockito doesn’t give you hangover because the tests are very readable and they produce clean verification errors. , n. It lets you write beautiful tests with a clean & simple API. Code below. junit. Java Exception Handling; How the Exception Handling Works in Java I am using spring MVC testing: In my test case, I am passing an invalid Bar object(age with zero). example. *; @Test public void test MockedMethodThrowsException() Feb 18, 2025 · Examples of Mocking Exceptions in Mockito. This is particularly useful when you want to test how your code handles exceptions from dependencies. out. First the stuff that will be tested: @Component public class Blam { public void blamIt() { System. Handling exceptions in Mockito tests. This allows us, to write unit tests, that ensure our try-catch-blocks work as expected! Important to know: In case we throw checked exceptions, the compiler doesn’t let us throw checked exceptions that are not declared on the method! Mockito FAQ The source code examples of this guide are well-tested with our local development environment and you can use these code examples as bug-free. Throwing Exceptions. Aug 11, 2020 · Example Project. Master exception handling in Mockito with practical examples and expert tips for better unit tests. Mockito - Exception Handling Example :-Step 1 − Create an interface called CalculatorService to provide mathematical functions. This means that if we pass Exception as the expected exception type, any exception thrown will make the assertion succeed since Exception is the super-type for all exceptions. Dedicated local streams across North America, Europe, and Asia-Pacific will explore the latest Java AI models to develop LLM apps and agents, learning best practices for app modernization with AI-assisted dev tools, learning the latest in Java frameworks Apr 26, 2013 · Mockito fully supports stubbing methods to throw an exception, AssertJ is not necessary. method from the org. Assert. The MethodArgumentNotValidException is being thrown, but it is May 11, 2024 · Connect with experts from the Java community, Microsoft, and partners to “Code the Future with AI” JDConf 2025, on April 9 - 10. There are three main ways to handle exceptions in Mockito tests: Catching exceptions in the test code; Ignoring exceptions in the test code; Throwing exceptions in the test code Easy to understand tutorials with lots of sample codes in programming languages Java, Python, JavaScript, PHP, HTML, CSS, C++, C# etc. create(error) . The assertThrows() will FAIL: If no exception is thrown from the executable block; If an exception of a different type is thrown; For example, in below example "1" is a valid number so no exception will be thrown. equals("Our message") ). junit 4. Handling Exceptions in Unit Tests. assertEquals; import static org. thenThrow(), doThrow(), and using Spring Retry to effectively test retries in your code. While the previous section demonstrated a basic example of mocking exception throwing, Mockito offers more advanced features for handling exceptions during testing. Some of the examples of mocking exceptions in Mockito are: 1. Learn how to simulate API failures using Mockito in unit tests, with detailed examples for non-void and void methods, exception handling, and best practices. springframework. It can also throw a number of exceptions so I'd like to test those exceptions being thrown. Key Features for Handling Exceptions in Mockito Simulating Exceptions: Mockito allows you to simulate exceptions from mocked methods using the thenThrow() method. We want to test that the correct exception is thrown and handled appropriately. When the mocked method is called, the `Throwable` object will be thrown. When writing Mockito tests, it is important to handle exceptions that may be thrown by the code under test. Mar 17, 2024 · Connect with experts from the Java community, Microsoft, and partners to “Code the Future with AI” JDConf 2025, on April 9 - 10. Here's an example of how you can use these methods to mock and assert a thrown exception: May 20, 2017 · What is mockito? Mockito is a mocking framework that tastes really good. d. Dedicated local streams across North America, Europe, and Asia-Pacific will explore the latest Java AI models to develop LLM apps and agents, learning best practices for app modernization with AI-assisted dev tools, learning the latest in Java frameworks Failing to correctly assert the exception handling logic may result in passing tests that should fail. While Mockito offers a rich API for various testing scenarios, for exception mocking, we’ll focus predominantly on the when-thenThrow method chain. All attempts have failed with the same reason: The method when Apr 25, 2021 · Mockito has the answer: Instead of declaring a return value, we can declare an exception to be thrown. Mockito allows you to stub multiple calls with different behaviors. Mar 26, 2025 · Furthermore, it’s important to note that this assertion is satisfied when the enclosed code throws an exception of type NumberFormatException or any of its derived types. . isIntance(. blamIt(); } } // Example of handling an exception in Mockito import static org. Writing Junit test cases for @GetMapping, @PostMapping, @PutMapping and @DeleteMapping using MockMvc. Jan 31, 2024 · Mockito Essentials for Exception Mocking. This guide covers techniques like when(). ) will return true even if the thrown exception is of a child type. Mar 30, 2025 · Advanced Exception Handling Testing. Mockito can also be used to mock checked exceptions (Exceptions are checked at compile time, forcing the programmer to handle them explicitly), which require explicit handling in code. *; import org. bzl zdul wyfzz crxzc vvsdq vyvzmvpp mntd ltgyi mvpt gbgd qczm fgheb uqjrwck gnsxl shluvt