BAEL-3231: Add usage example for MockitoJUnit.rule() (#8304)

testing-modules/mockito/src/test/java/com/baeldung/mockito/MockitoInitWithMockitoJUnitRuleUnitTest.java

@@ -0,0 +1,28 @@
+package com.baeldung.mockito;
+
+import org.junit.Rule;
+import org.junit.Test;
+import org.mockito.Mock;
+import org.mockito.junit.MockitoJUnit;
+import org.mockito.junit.MockitoRule;
+
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.when;
+
+public class MockitoInitWithMockitoJUnitRuleUnitTest {
+
+    @Rule
+    public MockitoRule initRule = MockitoJUnit.rule();
+    
+    @Mock
+    private List<String> mockedList;
+
+    @Test
+    public void whenUsingMockitoJUnitRule_thenMocksInitialized() {
+        when(mockedList.size()).thenReturn(41);
+
+        assertThat(mockedList.size()).isEqualTo(41);
+    }
+}