How to use toStackTrace method of org.mockito.exceptions.base.StackTraceBuilder class

You need a Method object and a Class object. As per your comment, Mockito cannot mock a Method, so you'll need a real one. I haven't tested this, but I believe this would work. Instead of:

when(mockContext.getMethod().getName()).thenReturn("someMethod");
when(mockContext.getMethod().getDeclaringClass().getName()).thenReturn("someClass");

You need:

// any method will do, but here is an example of how to get one.
Method testMethod = this.getClass().getMethod("logCallTest");

when(mockContext.getMethod()).thenReturn(testMethod);

Obviously, getName() will not return "someMethod" anymore and getDeclaringClass().getName() will return the name of this test class (in the example), but although you couldn't pick what they return, what they return is still deterministic, so you should be able to verify anything you need. (Of course, if you needed to spy or verify that a call was made on the Method object itself, you're still stuck.)

User Matcher documentation isA() method.

public static <T> T isA(java.lang.Class<T> clazz)

That will solve your problem.

verify(foo).putObject(isA(SomeClass.class));

While a partial mock isn't a bad idea, you might find your code easier to follow if you use an ArgumentCaptor instead to get the values after the fact. It's a special argument matcher that keeps track of the value it matches.

// initialized with MockitoAnnotations.initMocks();
@Captor ArgumentCaptor<Integer> offsetCaptor;
@Captor ArgumentCaptor<float[]> floatsCaptor;
@Mock Bar bar;

@Test
public void valuesShouldBeCloseEnough() {
  Sut sut = new Sut(bar);
  sut.doSomething();
  verify(bar).setFoo(offsetCaptor.capture(), floatsCaptor.capture());

  // check values with assertValuesAreCloseEnough, declared elsewhere
  assertValuesAreCloseEnough(offsetCaptor.getValue(), floatsCaptor.getValue());
}

Mockito 1.8.1 introduced anyVararg() matcher:

when(a.b(anyInt(), anyInt(), Matchers.<String>anyVararg())).thenReturn(b);

Also see history for this: https://code.google.com/archive/p/mockito/issues/62

Edit new syntax after deprecation:

when(a.b(anyInt(), anyInt(), ArgumentMatchers.<String>any())).thenReturn(b);

You can use

  Mockito.doAnswer(new Answer<Void>() {
        @Override
        public Void answer(InvocationOnMock invocation) throws Throwable {
            //DO SOMETHING
            return null;
        }
    }).when(...).remove(Matchers.<String>anyVararg());

From the Javadoc:

Use doAnswer() when you want to stub a void method with generic Answer.

Stubbing voids requires different approach from Mockito.when(Object) because the compiler does not like void methods inside brackets...

Example:

    doAnswer(new Answer() {
    public Object answer(InvocationOnMock invocation) {
        Object[] args = invocation.getArguments();
        Mock mock = invocation.getMock();
        return null;
    }}).when(mock).someMethod();

See examples in javadoc for Mockito

After doing a bit more research, it seems that PowerMockito.spy() and PowerMockito.doReturn() are what is required here:

package com.richashworth.powermockexample;

import org.junit.Before;
import org.junit.BeforeClass;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.powermock.api.mockito.PowerMockito;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;

import java.util.ArrayList;
import java.util.List;

import static org.junit.Assert.assertEquals;


@RunWith(PowerMockRunner.class)
@PrepareForTest({DataProvider.class})
public class ResultsWriterTest {

    private static List<String> mockData = new ArrayList<String>();
    private ResultsWriter resultsWriter;

    @BeforeClass
    public static void setUpOnce() {
        final String firstLine = "Line 1";
        final String secondLine = "Line 2";
        mockData.add(firstLine);
        mockData.add(secondLine);
    }

    @Before
    public void setUp() {
        resultsWriter = new ResultsWriter();
    }

    @Test
    public void testGetDataAsString() throws Exception {
        PowerMockito.spy(DataProvider.class);
        PowerMockito.doReturn(mockData).when(DataProvider.class, "readFile");

        final String expectedData = "Line 1\nLine 2\n";
        final String returnedString = resultsWriter.getDataAsString();

        assertEquals(expectedData, returnedString);
    }

}

For further details and the complete code listing, check out my blog post here: https://richashworth.com/post/turbocharge-your-mocking-framework-with-powermock/

For any other type you can use any(). This will match an argument of given type:

any(UUID.class)

You can find more information in the documentation.

You pass raw value there (as error already mentioned). Use matcher instead like this:

import static org.mockito.Mockito.*;

...
when(barObj.bar(eq(10), any(Date.class))
   .thenReturn(10)

If you are using Spring (the spring-test library specifically), you can simply use ReflectionTestUtils.setField instead of Whitebox.setInternalState