[BAEL-1858] - How to mock a static method using JMockit (#4925)

testing-modules/mocks/jmockit/src/main/java/com/baeldung/mocks/jmockit/AppManager.java

@@ -0,0 +1,26 @@
+package com.baeldung.mocks.jmockit;
+
+import java.util.Random;
+
+public class AppManager {
+
+    public boolean managerResponse(String question) {
+        return AppManager.isResponsePositive(question);
+    }
+
+    public static boolean isResponsePositive(String value) {
+        if (value == null)
+            return false;
+        int orgLength = value.length();
+        int randomNumber = randomNumber();
+        return orgLength == randomNumber ? true : false;
+    }
+
+    private static int randomNumber() {
+        return new Random().nextInt(7);
+    }
+
+    private static Integer stringToInteger(String num) {
+        return Integer.parseInt(num);
+    }
+}

testing-modules/mocks/jmockit/src/test/java/com/baeldung/mocks/jmockit/AppManagerUnitTest.java

@@ -0,0 +1,44 @@
+package com.baeldung.mocks.jmockit;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import mockit.Deencapsulation;
+import mockit.Mock;
+import mockit.MockUp;
+
+public class AppManagerUnitTest {
+
+    private AppManager appManager;
+
+    @BeforeEach
+    public void setUp() {
+        appManager = new AppManager();
+    }
+
+    @Test
+    public void givenAppManager_whenStaticMethodCalled_thenValidateExpectedResponse() {
+        new MockUp<AppManager>() {
+            @Mock
+            public boolean isResponsePositive(String value) {
+                return false;
+            }
+        };
+
+        Assertions.assertFalse(appManager.managerResponse("Why are you coming late?"));
+    }
+
+    @Test
+    public void givenAppManager_whenPrivateStaticMethod_thenValidateExpectedResponse() {
+        final int response = Deencapsulation.invoke(AppManager.class, "stringToInteger", "110");
+        Assertions.assertEquals(110, response);
+    }
+
+    @Test
+    public void givenAppManager_whenPrivateStaticMethod_thenExpectException() {
+        Assertions.assertThrows(IllegalArgumentException.class, () -> {
+            Deencapsulation.invoke(AppManager.class, "stringToInteger", "11r");
+        });
+    }
+}