Mockito when/thenReturn & doReturn/when patterns behaviour

MockitoBehaviour.java

import org.junit.Assert;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.Mock;
import org.mockito.runners.MockitoJUnitRunner;
import java.util.Map;
import static org.mockito.Mockito.doReturn;
import static org.mockito.Mockito.when;

@RunWith(MockitoJUnitRunner.class)
public class MockitoTest {


    @Mock
    Map<String, Integer> map;

    /** (Succeeds)
     * Map will always return:
     * - 1, when queried with "first"
     * - 2, when queried with "second"
     */
    @Test
    public void testChainedWhenWithDifferentParams() {
        when(map.get("first"))
                .thenReturn(1);
        when(map.get("second"))
                .thenReturn(2);

        Assert.assertEquals(Integer.valueOf(1), map.get("first"));
        Assert.assertEquals(Integer.valueOf(2), map.get("second"));
    }

    /** (Fails)
     * Map will always return:
     * - 2, when asked with first
     *
     * The second command overrides the first expectation
     */
    @Test
    public void testChainedWhenWithSameParam() {
        when(map.get("first"))
                .thenReturn(1);
        when(map.get("first"))
                .thenReturn(2);

        Assert.assertEquals(Integer.valueOf(1), map.get("first"));
        Assert.assertEquals(Integer.valueOf(2), map.get("first"));
    }

    /** (Succeeds)
     * Map will return:
     * - 1, at the first time it's invoked with "first"
     * - 2, all the subsequent times when invoked with "first"
     */
    @Test
    public void testChainedThenReturnWithSameParam() {
        when(map.get("first"))
                .thenReturn(1)
                .thenReturn(2);

        Assert.assertEquals(Integer.valueOf(1), map.get("first"));
        Assert.assertEquals(Integer.valueOf(2), map.get("first"));
    }

    /** (Succeeds)
     * Map will always return:
     * - 1, when invoked with "first"
     * - 2, when invoked with "second"
     */
    @Test
    public void testChainedDoReturnWithDifferentParams() {
        doReturn(1)
                .when(map).get("first");
        doReturn(2)
                .when(map).get("second");

        Assert.assertEquals(Integer.valueOf(1), map.get("first"));
        Assert.assertEquals(Integer.valueOf(2), map.get("second"));
    }

    /** (Fails)
     * Map will always return:
     * - 2, when asked with first
     *
     * The second command overrides the first expectation
     */
    @Test
    public void testChainedDoReturnWithSameParam() {
        doReturn(1)
                .when(map).get("first");
        doReturn(2)
                .when(map).get("first");

        Assert.assertEquals(Integer.valueOf(1), map.get("first"));
        Assert.assertEquals(Integer.valueOf(2), map.get("first"));
    }


}