Group testing modules (#3014)

* move security content from spring-security-rest-full

* swagger update

* move query language to new module

* rename spring-security-rest-full to spring-rest-full

* group persistence modules

* group testing modules

* try fix conflict

testing-modules/junit-5/src/test/java/com/baeldung/NestedUnitTest.java

@@ -0,0 +1,81 @@
+package com.baeldung;
+
+import java.util.EmptyStackException;
+import java.util.Stack;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
+
+public class NestedUnitTest {
+    Stack<Object> stack;
+    boolean isRun = false;
+
+    @Test
+    @DisplayName("is instantiated with new Stack()")
+    void isInstantiatedWithNew() {
+        new Stack<Object>();
+    }
+
+    @Nested
+    @DisplayName("when new")
+    class WhenNew {
+
+        @BeforeEach
+        void init() {
+            stack = new Stack<Object>();
+        }
+
+        @Test
+        @DisplayName("is empty")
+        void isEmpty() {
+            Assertions.assertTrue(stack.isEmpty());
+        }
+
+        @Test
+        @DisplayName("throws EmptyStackException when popped")
+        void throwsExceptionWhenPopped() {
+            Assertions.assertThrows(EmptyStackException.class, () -> stack.pop());
+        }
+
+        @Test
+        @DisplayName("throws EmptyStackException when peeked")
+        void throwsExceptionWhenPeeked() {
+            Assertions.assertThrows(EmptyStackException.class, () -> stack.peek());
+        }
+
+        @Nested
+        @DisplayName("after pushing an element")
+        class AfterPushing {
+
+            String anElement = "an element";
+
+            @BeforeEach
+            void init() {
+                stack.push(anElement);
+            }
+
+            @Test
+            @DisplayName("it is no longer empty")
+            void isEmpty() {
+                Assertions.assertFalse(stack.isEmpty());
+            }
+
+            @Test
+            @DisplayName("returns the element when popped and is empty")
+            void returnElementWhenPopped() {
+                Assertions.assertEquals(anElement, stack.pop());
+                Assertions.assertTrue(stack.isEmpty());
+            }
+
+            @Test
+            @DisplayName("returns the element when peeked but remains not empty")
+            void returnElementWhenPeeked() {
+                Assertions.assertEquals(anElement, stack.peek());
+                Assertions.assertFalse(stack.isEmpty());
+            }
+        }
+    }
+}