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Using Mockito's generic "any()" method

People also ask

What does Mockito any () do?

Mockito allows us to create mock objects and stub the behavior for our test cases. We usually mock the behavior using when() and thenReturn() on the mock object.

Does Mockito any match null?

Since Mockito any(Class) and anyInt family matchers perform a type check, thus they won't match null arguments.

How do I use Mockito doNothing?

Mockito 's doNothing() is used when you want to test void methods because void methods do not return anything so there is no way you can verify using assert. These void methods may be anywhere, for example, in service class, in dao class, etc.

What are matchers in Mockito?

What are Matchers? Matchers are like regex or wildcards where instead of a specific input (and or output), you specify a range/type of input/output based on which stubs/spies can be rest and calls to stubs can be verified. All the Mockito matchers are a part of 'Mockito' static class.


This should work

import static org.mockito.ArgumentMatchers.any;
import static org.mockito.Mockito.verify;

verify(bar).DoStuff(any(Foo[].class));

Since Java 8 you can use the argument-less any method and the type argument will get inferred by the compiler:

verify(bar).doStuff(any());

Explanation

The new thing in Java 8 is that the target type of an expression will be used to infer type parameters of its sub-expressions. Before Java 8 only arguments to methods where used for type parameter inference (most of the time).

In this case the parameter type of doStuff will be the target type for any(), and the return value type of any() will get chosen to match that argument type.

This mechanism was added mainly to be able to compile lambda expressions, but it improves type inferences generally.


Primitive types

This doesn't work with primitive types, unfortunately:

public interface IBar {
    void doPrimitiveStuff(int i);
}

verify(bar).doPrimitiveStuff(any()); // Compiles but throws NullPointerException
verify(bar).doPrimitiveStuff(anyInt()); // This is what you have to do instead

The problem is that the compiler will infer Integer as the return value type of any(). Mockito will not be aware of this (due to type erasure) and return the default value for reference types, which is null. The runtime will try to unbox the return value by calling the intValue method on it before passing it to doStuff, and the exception gets thrown.


You can use Mockito.isA() for that:

import static org.mockito.Matchers.isA;
import static org.mockito.Mockito.verify;

verify(bar).doStuff(isA(Foo[].class));

http://site.mockito.org/mockito/docs/current/org/mockito/Matchers.html#isA(java.lang.Class)


As I needed to use this feature for my latest project (at one point we updated from 1.10.19), just to keep the users (that are already using the mockito-core version 2.1.0 or greater) up to date, the static methods from the above answers should be taken from ArgumentMatchers class:

import static org.mockito.ArgumentMatchers.isA;
import static org.mockito.ArgumentMatchers.any;

Please keep this in mind if you are planning to keep your Mockito artefacts up to date as possibly starting from version 3, this class may no longer exist:

As per 2.1.0 and above, Javadoc of org.mockito.Matchers states:

Use org.mockito.ArgumentMatchers. This class is now deprecated in order to avoid a name clash with Hamcrest * org.hamcrest.Matchers class. This class will likely be removed in version 3.0.

I have written a little article on mockito wildcards if you're up for further reading.