Unable to mock static methods with parameters using Mockito

问题

I am trying to use some of the new features of Mockito, specifically mocking of static methods.

I am able to get it to work when the method I am mocking has no parameters, but for some reason it will not work if the method has any parameters.

As the example below is written, the test assertEquals( "bar", Foo.foo() ) works but the test assertEquals(2, map.size() ) fails as no behavior has been defined for the mocked class.

fooMock.when(Foo::genMap).thenCallRealMethod() gives the follwing compile time errors:

The type Foo does not define genMap() that is applicable here
The method when(MockedStatic.Verification) in the type MockedStatic is not applicable for the arguments (Foo:: genMap)

fooMock.when( (String s)->Foo.genMap(s) ).thenCallRealMethod() gives these compile time errors:

The method when(MockedStatic.Verification) in the type MockedStatic is not applicable for the arguments ((String s) -> {})
Lambda expression's signature does not match the signature of the functional interface method apply()

Unit Test:

@RunWith(MockitoJUnitRunner.class)
public class FooTest {

    @Test
    public void fooTest(){  
        try( MockedStatic<Foo> fooMock = Mockito.mockStatic(Foo.class) ){
            fooMock.when(Foo::foo).thenReturn("bar");
            assertEquals( "bar", Foo.foo() );
            //fooMock.when(Foo::genMap).thenCallRealMethod();
            //fooMock.when( (String s)->Foo.genMap(s) ).thenCallRealMethod();
            Map<String, String> map = Foo.genMap("1=one 2=two");
            assertEquals(2, map.size() );
        }
    }

}

Class to be mocked

public class Foo {

    public static String foo() {
        return "foo";
    }

    public static Map<String, String> genMap(String str){
        Map<String, String> map = new HashMap<String, String>();
        for(String subStr : str.split(" ")) {
            String[] parts = subStr.split("=");
            map.put(parts[0], parts[1]);
        }
        return map;
    }
}

It looks like it is a simply a syntax issue, I am not super familiar with method references but I cannot figure out what the proper syntax would be.

回答1:

This is the correct syntax

fooMock.when( () -> Foo.genMap(any()) ).thenCallRealMethod();

anyString() can be used, but there shouldn't be any difference because it's not ambiguous.

来源：https://stackoverflow.com/questions/64809471/unable-to-mock-static-methods-with-parameters-using-mockito

标签

java

unit-testing

lambda

mockito

static-methods