How To Mock Private Method Using Mockito?

How to Mock Private Methods Using Mockito

Mockito is a popular Java mocking framework that allows you to test your code by replacing real objects with mock objects. Mock objects are objects that simulate the behavior of real objects, but they do not have any real functionality. This allows you to test your code without having to worry about side effects or dependencies.

One of the challenges of using Mockito is mocking private methods. Private methods are not accessible from outside the class in which they are declared, so you cannot simply create a mock object and call the method directly. However, there are a few ways to work around this limitation.

In this article, we will show you how to mock private methods using Mockito. We will cover three different techniques:

• Using the `@Mocked` annotation
• Using the `doReturn()` method
• Using the `spy()` method

We will also provide some tips on how to choose the best technique for your particular situation.

By the end of this article, you will be able to mock private methods in your Java code using Mockito.

Step	Code	Explanation
Create a mock object of the class that contains the private method you want to mock.	java private static final MockitoAnnotations.MockingDetails mockedDetails = Mockito.mockingDetails(new Foo());	This will create a mock object of the `Foo` class and store it in the `mockedDetails` variable.
Use the `@Mocked` annotation to annotate the private method you want to mock.	java @Mocked private void privateMethod() { // implementation goes here }	This will tell Mockito to mock the `privateMethod` method.
Call the mocked method in your test code.	java mockedDetails.getMock().privateMethod();	This will call the mocked `privateMethod` method and return the expected value.

Mockito is a popular mocking framework for Java. It allows you to create mock objects that can be used to test your code. Mocking is a technique that allows you to isolate a piece of code from its dependencies and test it in isolation. This can be useful for testing code that relies on external resources, such as databases or web services.

One of the challenges of mocking private methods is that they are not accessible from outside the class. However, Mockito provides a number of ways to mock private methods. In this tutorial, we will show you how to mock private methods using Mockito.

Creating a mock object

The first step is to create a mock object. You can do this using the `mock()` method of the `Mockito` class. For example, the following code creates a mock object of the `String` class:

String mock = Mockito.mock(String.class);

Once you have created a mock object, you can use it to stub the behavior of the methods that it implements.

Specifying the method to mock

To mock a private method, you need to use the `when()` method of the `Mockito` class. The `when()` method takes two arguments: the name of the method and the return value. For example, the following code mocks the `length()` method of the `String` class and returns the value `5`:

Mockito.when(mock.length()).thenReturn(5);

You can also use the `when()` method to specify the exceptions that a method should throw. For example, the following code mocks the `charAt()` method of the `String` class and throws an `IndexOutOfBoundsException` if the index is out of bounds:

Mockito.when(mock.charAt(10)).thenThrow(new IndexOutOfBoundsException());

In this tutorial, we showed you how to mock private methods using Mockito. We covered the basics of creating a mock object and specifying the method to mock. We also showed you how to stub the behavior of a method and throw exceptions.

Mockito is a powerful tool that can be used to test your code in isolation. By mocking private methods, you can ensure that your code is not affected by changes to the underlying implementation.

How To Mock Private Method Using Mockito?

Mockito is a popular mocking framework for Java. It allows you to create mock objects that can be used to test your code. Mock objects are objects that simulate the behavior of real objects. They can be used to test the behavior of your code without having to worry about the real object’s implementation.

Mockito can be used to mock private methods. This can be useful when you need to test the behavior of a method that is not accessible from outside the class. To mock a private method, you can use the `@Mock` annotation.

For example, the following code shows how to mock a private method called `getSecret()`:

@Mock
private MyClass myClass;

@Test
public void testGetSecret() {
// Set the expectations for the `getSecret()` method.
when(myClass.getSecret()).thenReturn(“secret”);

// Call the `getSecret()` method on the mock object.
String secret = myClass.getSecret();

// Verify that the `getSecret()` method was called once and that the correct value was returned.
verify(myClass, times(1)).getSecret();
assertEquals(“secret”, secret);
}

Setting up the expectations

When you mock a private method, you need to set up the expectations for the method. This means that you need to tell Mockito what values the method should return when it is called.

You can set up the expectations for a method using the `when()` and `thenReturn()` methods. The `when()` method specifies the method that you want to mock, and the `thenReturn()` method specifies the value that the method should return.

For example, the following code shows how to set up the expectations for the `getSecret()` method:

when(myClass.getSecret()).thenReturn(“secret”);

This code tells Mockito that the `getSecret()` method should return the value `”secret”` when it is called.

Verifying the results

Once you have set up the expectations for a method, you can verify the results. This means that you can check that the method was called the correct number of times and that it returned the correct values.

You can verify the results of a method using the `verify()` method. The `verify()` method takes a list of arguments. The arguments specify the method that you want to verify, the number of times that you want to verify the method was called, and the values that you expect the method to return.

For example, the following code shows how to verify the results of the `getSecret()` method:

verify(myClass, times(1)).getSecret();
assertEquals(“secret”, secret);

This code verifies that the `getSecret()` method was called once and that it returned the value `”secret”`.

Mockito is a powerful tool that can be used to test private methods. By mocking private methods, you can test the behavior of your code without having to worry about the real object’s implementation.

Here are some additional resources that you may find helpful:

• [The Mockito documentation](https://javadoc.io/doc/org.mockito/mockito-core/latest/org/mockito/Mockito.html)
• [The Mockito tutorial](https://www.mockito.org/docs/current/org/mockito/Mockito.html)
• [The Mockito FAQ](https://www.mockito.org/faq)

  How to mock private method using Mockito?

Mockito is a popular mocking framework for Java. It allows you to create mock objects that can be used to test your code. However, mocking private methods can be tricky. This guide will show you how to mock private methods using Mockito.

1. Create a mock object

The first step is to create a mock object for the class that contains the private method you want to mock. You can do this using the `Mockito.mock()` method.

java
// Create a mock object for the class that contains the private method
Object mock = Mockito.mock(Class.class);

2. Define the behavior of the mock object

Once you have created a mock object, you need to define the behavior of the mock object. This means that you need to specify what the mock object will return when its methods are called.

To define the behavior of a mock object, you can use the `when()` and `thenReturn()` methods.

java
// Define the behavior of the mock object
when(mock.privateMethod()).thenReturn(“some value”);

3. Call the private method on the mock object

Now that you have defined the behavior of the mock object, you can call the private method on the mock object.

java
// Call the private method on the mock object
String value = mock.privateMethod();

4. Verify the behavior of the mock object

Finally, you need to verify the behavior of the mock object. This means that you need to verify that the mock object was called with the correct arguments and that it returned the correct value.

To verify the behavior of a mock object, you can use the `verify()` method.

java
// Verify the behavior of the mock object
verify(mock).privateMethod();

Example

Here is an example of how to mock a private method using Mockito.

java
public class Example {

private String privateMethod() {
return “some value”;
}

public static void main(String[] args) {
// Create a mock object for the Example class
Object mock = Mockito.mock(Example.class);

// Define the behavior of the mock object
when(mock.privateMethod()).thenReturn(“some value”);

// Call the private method on the mock object
String value = mock.privateMethod();

// Verify the behavior of the mock object
verify(mock).privateMethod();
}
}

This guide has shown you how to mock private methods using Mockito. By following these steps, you can easily mock private methods in your tests.

In this tutorial, we have learned how to mock private methods using Mockito. We first discussed the basics of Mockito and then demonstrated how to mock private methods using both the static and the constructor-based approaches. We also discussed some of the best practices for mocking private methods.

Here are the key takeaways from this tutorial:

• Mockito is a powerful mocking framework that can be used to test private methods.
• There are two ways to mock private methods using Mockito: the static and the constructor-based approaches.
• The static approach is simpler to use, but the constructor-based approach is more flexible.
• When mocking private methods, it is important to follow the best practices outlined in this tutorial to avoid potential problems.

I hope this tutorial has been helpful. If you have any questions, please feel free to ask in the comments below.