feat: Add JUnit 5 and AssertJ for testing

This commit introduces a comprehensive testing framework to the project by adding JUnit 5 and AssertJ.

Key changes include:
- Addition of `junit-jupiter-api`, `junit-jupiter-engine`, `junit-platform-launcher`, and `junit-platform-console` dependencies to `pom.xml`.
- Integration of `assertj-core` for fluent assertions.
- Configuration of the `maven-surefire-plugin` to execute tests during the build lifecycle.
- A new test, `JsonParserTests.java`, has been added to validate the JSON parsing functionality and serve as an example of the testing setup.

Author: simbo1905

pom.xml

@@ -21,8 +21,43 @@
   <properties>
     <maven.compiler.source>21</maven.compiler.source>
     <maven.compiler.target>21</maven.compiler.target>
+    <junit.jupiter.version>5.13.1</junit.jupiter.version>
+    <junit.platform.version>1.13.1</junit.platform.version>
   </properties>
 
+    <dependencies>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-api</artifactId>
+            <version>${junit.jupiter.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-engine</artifactId>
+            <version>${junit.jupiter.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.platform</groupId>
+            <artifactId>junit-platform-launcher</artifactId>
+            <version>${junit.platform.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.platform</groupId>
+            <artifactId>junit-platform-console</artifactId>
+            <version>${junit.platform.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>3.26.3</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
   <build>
     <plugins>
       <plugin>
@@ -34,6 +69,11 @@
           <target>21</target>
         </configuration>
       </plugin>
+        <plugin>
+            <groupId>org.apache.maven.plugins</groupId>
+            <artifactId>maven-surefire-plugin</artifactId>
+            <version>3.2.5</version>
+        </plugin>
     </plugins>
   </build>
 </project>

src/test/java/jdk/sandbox/internal/util/json/JsonParserTests.java

@@ -0,0 +1,53 @@
+package jdk.sandbox.internal.util.json;
+
+import jdk.sandbox.java.util.json.JsonArray;
+import jdk.sandbox.java.util.json.JsonBoolean;
+import jdk.sandbox.java.util.json.JsonNumber;
+import jdk.sandbox.java.util.json.JsonObject;
+import jdk.sandbox.java.util.json.JsonString;
+import org.junit.jupiter.api.Test;
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class JsonParserTests {
+
+    @Test
+    void testParseComplexJson() {
+        String json = """
+                {
+                    "name": "John Doe",
+                    "age": 30,
+                    "isStudent": false,
+                    "courses": [
+                        {"title": "History", "credits": 3},
+                        {"title": "Math", "credits": 4}
+                    ],
+                    "address": {
+                        "street": "123 Main St",
+                        "city": "Anytown"
+                    }
+                }
+                """;
+
+        JsonParser parser = new JsonParser(json.toCharArray());
+        JsonObject jsonObject = (JsonObject) parser.parseRoot();
+
+        assertThat(((JsonString) jsonObject.members().get("name")).value()).isEqualTo("John Doe");
+        assertThat(((JsonNumber) jsonObject.members().get("age")).toNumber().longValue()).isEqualTo(30L);
+        assertThat(((JsonBoolean) jsonObject.members().get("isStudent")).value()).isFalse();
+
+        JsonArray courses = (JsonArray) jsonObject.members().get("courses");
+        assertThat(courses.values()).hasSize(2);
+
+        JsonObject course1 = (JsonObject) courses.values().get(0);
+        assertThat(((JsonString) course1.members().get("title")).value()).isEqualTo("History");
+        assertThat(((JsonNumber) course1.members().get("credits")).toNumber().longValue()).isEqualTo(3L);
+
+        JsonObject course2 = (JsonObject) courses.values().get(1);
+        assertThat(((JsonString) course2.members().get("title")).value()).isEqualTo("Math");
+        assertThat(((JsonNumber) course2.members().get("credits")).toNumber().longValue()).isEqualTo(4L);
+
+        JsonObject address = (JsonObject) jsonObject.members().get("address");
+        assertThat(((JsonString) address.members().get("street")).value()).isEqualTo("123 Main St");
+        assertThat(((JsonString) address.members().get("city")).value()).isEqualTo("Anytown");
+    }
+}