Add Mockito, upgrade JUnit

pom.xml

@@ -34,6 +34,11 @@
   </dependencyManagement>
 
   <dependencies>
+    <dependency>
+      <groupId>org.mockito</groupId>
+      <artifactId>mockito-core</artifactId>
+      <version>5.19.0</version>
+    </dependency>
     <dependency>
       <groupId>org.projectlombok</groupId>
       <artifactId>lombok</artifactId>
@@ -41,9 +46,9 @@
       <scope>provided</scope>
     </dependency>
     <dependency>
-      <groupId>junit</groupId>
-      <artifactId>junit</artifactId>
-      <version>3.8.1</version>
+      <groupId>org.junit.jupiter</groupId>
+      <artifactId>junit-jupiter</artifactId>
+      <version>5.13.4</version>
     </dependency>
     <dependency>
       <groupId>org.lwjgl</groupId>