BAEL-5846 - Testing methods that call System.exit (#12952)

* BAEL-5846 - Testing methods that call System.exit

* BAEL-5846 - Testing methods that call System.exit - JMockit implementation

* BAEL-5846 - Testing methods that call System.exit - Changing test case names

* BAEL-5846 - Testing methods that call System.exit - changing test names

* BAEL-5777 - Mocking a singleton with Mockito - review incorporation

testing-modules/junit-5-advanced/pom.xml

@@ -14,4 +14,36 @@
         <version>1.0.0-SNAPSHOT</version>
     </parent>
 
+    <dependencies>
+        <dependency>
+            <groupId>com.github.stefanbirkner</groupId>
+            <artifactId>system-lambda</artifactId>
+            <version>1.2.1</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.jmockit</groupId>
+            <artifactId>jmockit</artifactId>
+            <version>${jmockit.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+    <plugins>
+        <plugin>
+            <groupId>org.apache.maven.plugins</groupId>
+            <artifactId>maven-surefire-plugin</artifactId>
+            <configuration>
+                <argLine>
+                    -javaagent:${settings.localRepository}/org/jmockit/jmockit/${jmockit.version}/jmockit-${jmockit.version}.jar
+                </argLine>
+                <disableXmlReport>true</disableXmlReport>
+            </configuration>
+        </plugin>
+    </plugins>
+    </build>
+    <properties>
+        <jmockit.version>1.49</jmockit.version>
+    </properties>
 </project>

testing-modules/junit-5-advanced/src/main/java/com/baeldung/systemexit/Task.java

@@ -0,0 +1,17 @@
+package com.baeldung.systemexit;
+
+public class Task {
+    private String name;
+
+    public Task(String name) {
+        this.name = name;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+}

testing-modules/junit-5-advanced/src/main/java/com/baeldung/systemexit/TaskDAO.java

@@ -0,0 +1,8 @@
+package com.baeldung.systemexit;
+
+import java.io.IOException;
+
+public class TaskDAO {
+    public void save(Task task) throws Exception {
+    }
+}

testing-modules/junit-5-advanced/src/main/java/com/baeldung/systemexit/TaskService.java

@@ -0,0 +1,18 @@
+package com.baeldung.systemexit;
+
+public class TaskService {
+
+    private final TaskDAO taskDAO;
+
+    public TaskService(TaskDAO taskDAO) {
+        this.taskDAO = taskDAO;
+    }
+
+    public void saveTask(Task task) {
+        try {
+            taskDAO.save(task);
+        } catch (Exception e) {
+            System.exit(1);
+        }
+    }
+}

testing-modules/junit-5-advanced/src/test/java/com/baeldung/systemexit/TaskServiceJMockitUnitTest.java

@@ -0,0 +1,33 @@
+package com.baeldung.systemexit;
+
+import mockit.Mock;
+import mockit.MockUp;
+import org.junit.Test;
+import org.junit.jupiter.api.Assertions;
+
+import static org.mockito.Mockito.doThrow;
+import static org.mockito.Mockito.mock;
+
+public class TaskServiceJMockitUnitTest {
+
+    @Test
+    public void givenDAOThrowsException_whenSaveTaskIsCalled_thenSystemExitIsCalled() throws Exception {
+
+        new MockUp<System>() {
+            @Mock
+            public void exit(int value) {
+                throw new RuntimeException(String.valueOf(value));
+            }
+        };
+
+        Task task = new Task("test");
+        TaskDAO taskDAO = mock(TaskDAO.class);
+        TaskService service = new TaskService(taskDAO);
+        try {
+            doThrow(new NullPointerException()).when(taskDAO).save(task);
+            service.saveTask(task);
+        } catch (RuntimeException runtimeException) {
+            Assertions.assertEquals("1", runtimeException.getMessage());
+        }
+    }
+}

testing-modules/junit-5-advanced/src/test/java/com/baeldung/systemexit/TaskServiceSecurityManagerUnitTest.java

@@ -0,0 +1,43 @@
+package com.baeldung.systemexit;
+
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.security.Permission;
+
+import static org.mockito.Mockito.*;
+
+class TaskServiceSecurityManagerUnitTest {
+
+    @BeforeEach
+    void setUp() {
+        System.setSecurityManager(new NoExitSecurityManager());
+    }
+
+    @Test
+    void givenDAOThrowsException_whenSaveTaskIsCalled_thenSystemExitIsCalled() throws Exception {
+        Task task = new Task("test");
+        TaskDAO taskDAO = mock(TaskDAO.class);
+        TaskService service = new TaskService(taskDAO);
+        try {
+            doThrow(new NullPointerException()).when(taskDAO).save(task);
+            service.saveTask(task);
+        } catch (RuntimeException e) {
+            Assertions.assertEquals("1", e.getMessage());
+        }
+    }
+
+    private static class NoExitSecurityManager extends SecurityManager {
+        @Override
+        public void checkPermission(Permission perm) {
+        }
+
+        @Override
+        public void checkExit(int status) {
+            super.checkExit(status);
+            throw new RuntimeException(String.valueOf(status));
+        }
+    }
+}

testing-modules/junit-5-advanced/src/test/java/com/baeldung/systemexit/TaskServiceSystemLambdaUnitTest.java

@@ -0,0 +1,23 @@
+package com.baeldung.systemexit;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.Test;
+
+import static com.github.stefanbirkner.systemlambda.SystemLambda.catchSystemExit;
+import static org.mockito.Mockito.doThrow;
+import static org.mockito.Mockito.mock;
+
+public class TaskServiceSystemLambdaUnitTest {
+
+    @Test
+    public void givenDAOThrowsException_whenSaveTaskIsCalled_thenSystemExitIsCalled() throws Exception {
+        int statusCode = catchSystemExit(() -> {
+            Task task = new Task("test");
+            TaskDAO taskDAO = mock(TaskDAO.class);
+            TaskService service = new TaskService(taskDAO);
+            doThrow(new NullPointerException()).when(taskDAO).save(task);
+            service.saveTask(task);
+        });
+        Assertions.assertEquals(1, statusCode);
+    }
+}