Mockito – Verify multiple method calls with different arguments

Learn to write unit test which invokes a method multiple times with different arguments – and then verifies the method invocations and method arguments separately.

1. Verify multiple method calls with different arguments

The given unit test has mocked the HashMap class and invokes in put(key, value) code twice. It then verifies that method had been invoked twice. The test further verifies all the different method arguments separately.

import static org.junit.Assert.assertEquals;
import static org.mockito.Mockito.times;

import java.util.Arrays;
import java.util.HashMap;
import java.util.List;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.ArgumentCaptor;
import org.mockito.Captor;
import org.mockito.Mock;
import org.mockito.Mockito;
import org.mockito.junit.MockitoJUnitRunner;

@RunWith(MockitoJUnitRunner.class)
public class MockitoExample 
{
	@Mock
	HashMap<String, Integer> hashMap;

	@Captor
	ArgumentCaptor<String> keyCaptor;

	@Captor
	ArgumentCaptor<Integer> valueCaptor;

	@Test
	public void saveTest() 
	{
		hashMap.put("A", 10);
		hashMap.put("B", 20);
		
		//1. Verify method was invoked N times
		
		Mockito.verify(hashMap, times(2)).put(keyCaptor.capture(), valueCaptor.capture());

		List<String> keys = keyCaptor.getAllValues();
		List<Integer> values = valueCaptor.getAllValues();
		
		//2. Verify method argument values as list

		assertEquals(Arrays.asList("A", "B"), keys);
		assertEquals(Arrays.asList(Integer.valueOf(10), Integer.valueOf(20)), values);
		
		//3. Verify method arguments separately
		
		assertEquals("A", keys.get(0));
		assertEquals("B", keys.get(1));
		
		assertEquals(Integer.valueOf(10), values.get(0));
		assertEquals(Integer.valueOf(20), values.get(1));
	}
}

2. Explanation

To capture and verify all the method arguments passed to a method when it is invoked multiple times, we shall follow below steps:

• Use Mockito.verify(mock, times(n)) to verify if method was executed 'n' times.
• Create as many ArgumentCaptor instances as the number of arguments in the method. In above example, we tested the HashMap which work on key-value pairs, so we created two ArgumentCaptor instances – one for key and second for value.
• Use ArgumentCaptor.getAllValues() to retrieve all the values passed to one method parameter during all executions. It returns a List of passed argument values.
• We can use assertEquals(expected, result) to verify that expected multiple arguments match with the retrieved values from ArgumentCaptor.

Drop me your questions related to invoking a method multiple times and verify it’s method different arguments values in mockito based unit tests.

Happy Learning !!