Added unit test cases in givenX_whenY_thenZ format.

core-java-modules/core-java-reflection/src/main/java/com/baeldung/reflection/access/privatefields/Person.java

@@ -1,7 +1,7 @@
 package com.baeldung.reflection.access.privatefields;
 
 public class Person {
-    
+
     private String name;
 
     public String getName() {
@@ -12,7 +12,12 @@ public class Person {
         this.name = name;
     }
 
-    private String greet(String number) {
+    private String greet(String name) {
-        return "Hi " + Integer.parseInt(number);
+        return "Hello " + name;
     }
+
+    private int divideByZeroExample() {
+        return 1 / 0;
+    }
+
 }

core-java-modules/core-java-reflection/src/test/java/com/baeldung/reflection/access/privatefields/AccessPrivateFieldsUnitTest.java

@@ -1,36 +1,43 @@
 package com.baeldung.reflection.access.privatefields;
 
+import java.lang.reflect.Field;
+
 import org.junit.jupiter.api.Assertions;
-import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
 
 public class AccessPrivateFieldsUnitTest {
 
-    private static AccessPrivateProperties accessPrivateProperties;
+    @Test
+    public void whenGetField_thenSuccess() throws NoSuchFieldException, NullPointerException, IllegalArgumentException, IllegalAccessException {
+        Person person = new Person();
+        person.setName("John");
 
-    @BeforeAll
+        Field field = person.getClass()
-    public static void beforeAll() {
+            .getDeclaredField("name");
-        accessPrivateProperties = new AccessPrivateProperties();
+        field.setAccessible(true);
+
+        String name = (String) field.get(person);
+
+        Assertions.assertEquals("John", name);
     }
 
     @Test
-    public void testForNoSuchFieldException() {
+    public void givenInt_whenSetStringField_thenIllegalArgumentException() throws NoSuchFieldException, NullPointerException, IllegalArgumentException, IllegalAccessException {
-        Assertions.assertThrows(NoSuchFieldException.class, () -> accessPrivateProperties.accessPrivateFields("firstName", "John", true));
+        Person person = new Person();
+        Field field = person.getClass()
+            .getDeclaredField("name");
+        field.setAccessible(true);
+
+        Assertions.assertThrows(IllegalArgumentException.class, () -> field.setInt(person, 25));
     }
 
     @Test
-    public void testForIllegalAccessException() {
+    public void whenFieldNotSetAccessible_thenIllegalAccessException() throws NoSuchFieldException, NullPointerException, IllegalArgumentException, IllegalAccessException {
-        Assertions.assertThrows(IllegalAccessException.class, () -> accessPrivateProperties.accessPrivateFields("name", "John", false));
+        Person person = new Person();
-    }
+        Field field = person.getClass()
+            .getDeclaredField("name");
 
-    @Test
+        Assertions.assertThrows(IllegalAccessException.class, () -> field.set(person, "John"));
-    public void testForIllegalArgumentException() {
-        Assertions.assertThrows(IllegalArgumentException.class, () -> accessPrivateProperties.accessPrivateFields("name", 25, true));
-    }
-
-    @Test
-    public void testForNullPointerException() {
-        Assertions.assertThrows(NullPointerException.class, () -> accessPrivateProperties.accessPrivateFields(null, "John", true));
     }
 
 }

core-java-modules/core-java-reflection/src/test/java/com/baeldung/reflection/access/privatefields/AccessPrivateMethodsUnitTest.java

@@ -1,43 +1,56 @@
 package com.baeldung.reflection.access.privatefields;
 
 import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
 
 import org.junit.jupiter.api.Assertions;
-import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
 
 public class AccessPrivateMethodsUnitTest {
 
-    private static AccessPrivateProperties accessPrivateProperties;
+    @Test
+    public void whenGetMethod_thenSuccess() throws NoSuchMethodException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
+        Person person = new Person();
 
-    @BeforeAll
+        Method method = person.getClass()
-    public static void beforeAll() {
+            .getDeclaredMethod("greet", String.class);
-        accessPrivateProperties = new AccessPrivateProperties();
+        method.setAccessible(true);
+
+        String greetMessage = (String) method.invoke(person, "John");
+
+        Assertions.assertEquals("Hello John", greetMessage);
     }
 
     @Test
-    public void testForNoSuchMethodException() {
+    public void givenInt_whenInvokeMethod_thenIllegalArgumentException() throws NoSuchMethodException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
-        Assertions.assertThrows(NoSuchMethodException.class, () -> accessPrivateProperties.accessPrivateMethods("greeting", String.class, "5", true));
+        Person person = new Person();
+
+        Method method = person.getClass()
+            .getDeclaredMethod("greet", String.class);
+        method.setAccessible(true);
+
+        Assertions.assertThrows(IllegalArgumentException.class, () -> method.invoke(person, 25));
     }
 
     @Test
-    public void testForIllegalAccessException() {
+    public void whenMethodNotSetAccessible_thenIllegalAccessException() throws NoSuchMethodException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
-        Assertions.assertThrows(IllegalAccessException.class, () -> accessPrivateProperties.accessPrivateMethods("greet", String.class, "5", false));
+        Person person = new Person();
+
+        Method method = person.getClass()
+            .getDeclaredMethod("greet", String.class);
+
+        Assertions.assertThrows(IllegalAccessException.class, () -> method.invoke(person, "John"));
     }
 
     @Test
-    public void testForIllegalArgumentException() {
+    public void whenCallingMethodThrowsException_thenInvocationTargetException() throws NoSuchMethodException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
-        Assertions.assertThrows(IllegalArgumentException.class, () -> accessPrivateProperties.accessPrivateMethods("greet", String.class, 5, true));
+        Person person = new Person();
-    }
 
-    @Test
+        Method method = person.getClass()
-    public void testForNullPointerException() {
+            .getDeclaredMethod("divideByZeroExample");
-        Assertions.assertThrows(NullPointerException.class, () -> accessPrivateProperties.accessPrivateMethods(null, String.class, "5", true));
+        method.setAccessible(true);
-    }
 
-    @Test
+        Assertions.assertThrows(InvocationTargetException.class, () -> method.invoke(person));
-    public void testForInvocationTargetException() {
-        Assertions.assertThrows(InvocationTargetException.class, () -> accessPrivateProperties.accessPrivateMethods("greet", String.class, "John", true));
     }
 
 }