Add Class MockitoSpyTest

mockito/src/test/java/org/baeldung/mockito/MockitoSpyTest.java

@@ -0,0 +1,79 @@
+package org.baeldung.mockito;
+
+import static org.junit.Assert.assertEquals;
+import static org.mockito.Mockito.doReturn;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.verify;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Spy;
+import org.mockito.runners.MockitoJUnitRunner;
+
+@RunWith(MockitoJUnitRunner.class)
+public class MockitoSpyTest {
+
+    @Test
+    public void whenSpyOnList_thenCorrect() {
+        final List<String> list = new ArrayList<String>();
+        final List<String> spy = spy(list);
+
+        spy.add("one");
+        spy.add("two");
+
+        verify(spy).add("one");
+        verify(spy).add("two");
+
+        assertEquals(2, spy.size());
+    }
+
+    @Spy
+    List<String> spyList = new ArrayList<String>();
+
+    @Test
+    public void whenUseSpyAnnotation_thenCorrect() {
+        spyList.add("one");
+        spyList.add("two");
+
+        verify(spyList).add("one");
+        verify(spyList).add("two");
+
+        assertEquals(2, spyList.size());
+    }
+
+    @Test
+    public void whenStubASpy_thenStubbed() {
+        final List<String> list = new ArrayList<String>();
+        final List<String> spy = spy(list);
+
+        assertEquals(0, spy.size());
+
+        doReturn(100).when(spy).size();
+        assertEquals(100, spy.size());
+    }
+
+    @Test
+    public void whenCreateMock_thenCreated() {
+        final List mockedList = mock(List.class);
+
+        mockedList.add("one");
+        verify(mockedList).add("one");
+
+        assertEquals(0, mockedList.size());
+    }
+
+    @Test
+    public void whenCreateSpy_thenCreate() {
+        final List spy = spy(new ArrayList());
+
+        spy.add("one");
+        verify(spy).add("one");
+
+        assertEquals(1, spy.size());
+    }
+
+}