Matchers.any() for null value in Mockito

Question

Suppose I am having this object objectDemo which calls to the method objectDemoMethod with 2 parameters String and null. Now I want to verify with Mockito that this method was called:

objectDemo.objectDemoMethod("SAMPLE_STRING", null); 

I have written this:

Mockito.verify(objectDemo, Mockito.times(1)).objectDemoMethod(Matchers.any(String.class), null); 

but it's giving an error:

Invalid use of argument matchers for null value.

Is there any another way to pass null value?

Answer 1

The error message you are getting is expected since you are using argument matcher for only one argument and not the other. From Matchers Javadoc:

If you are using argument matchers, all arguments have to be provided by matchers.

Therefore, the fix is to use a matcher for the second parameter of the method as well. In this case, it would be a matcher matching null. Depending on the version of Mockito and Java, you can have:

• Starting with Mockito 2, you can use ArgumentMatchers.isNull(). This works with Java 8 and above:

  verify(objectDemo, times(1)).objectDemoMethod(any(String.class), isNull()); 

  Note that if you're running with Java 7 or older, you'll need an explicit cast to make this work, because the type inference in those versions of Java does not take into account the types of the method called:

  verify(objectDemo, times(1)).objectDemoMethod(any(String.class), (String) isNull()); 

• If you're using Mockito 1, you can use the Matchers.isNull(clazz) instead:

  verify(objectDemo, times(1)).objectDemoMethod(any(String.class), isNull(String.class)); 

For the Java ≤ 7 or Mockito 1 cases, the examples uses a case where the second parameter was of type String: it would need to be replaced with the actual type of the method parameter.

Answer 2

isNull seems to be deprecated

With Java 8 this method will be removed in Mockito 3.0. This method is only used for generic friendliness to avoid casting, this is not anymore needed in Java 8.

I think you could use nullable:

• public static <T> T nullable(Class<T> clazz)

You could use something like:

verify(objectDemo, times(1)).objectDemoMethod(any(String.class), nullable(String.class));