BAEL-6482 Code for the Matching Null With Mockito article

testing-modules/mockito-2/src/main/java/com/baeldung/nullmatcher/Helper.java

@@ -0,0 +1,9 @@
+package com.baeldung.nullmatcher;
+
+class Helper {
+
+    String concat(String a, String b) {
+        return a + b;
+    }
+
+}

testing-modules/mockito-2/src/main/java/com/baeldung/nullmatcher/Main.java

@@ -0,0 +1,11 @@
+package com.baeldung.nullmatcher;
+
+class Main {
+
+    Helper helper = new Helper();
+
+    String methodUnderTest() {
+        return helper.concat("Baeldung", null);
+    }
+
+}

testing-modules/mockito-2/src/test/java/com/baeldung/nullmatcher/MainUnitTest.java

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+package com.baeldung.nullmatcher;
+
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.isNull;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.Mockito;
+import org.mockito.MockitoAnnotations;
+
+class MainUnitTest {
+
+    @Mock
+    Helper helper;
+
+    @InjectMocks
+    Main main;
+
+    @BeforeEach
+    void openMocks() {
+        MockitoAnnotations.openMocks(this);
+    }
+
+    @Test
+    void whenMethodUnderTest_thenSecondParameterNull() {
+        main.methodUnderTest();
+        Mockito.verify(helper)
+          .concat("Baeldung", null);
+    }
+
+    @Test
+    void whenMethodUnderTest_thenSecondParameterNullWithMatchers() {
+        main.methodUnderTest();
+        Mockito.verify(helper)
+          .concat(any(), isNull());
+    }
+
+}