fixed gradle, added junit 4

build.gradle

 buildscript {
-    
 
     repositories {
         mavenLocal()
@@ -10,11 +9,11 @@ buildscript {
         google()
     }
     dependencies {
-        
 
     }
 }
 
+
 allprojects {
     apply plugin: "eclipse"
 
@@ -69,12 +68,14 @@ project(":desktop") {
 
 project(":core") {
     apply plugin: "java-library"
-	
+
 	java {
 		sourceCompatibility = JavaVersion.VERSION_1_8
 		targetCompatibility = JavaVersion.VERSION_1_8
 	}
 
+    repositories { jcenter() }
+
     dependencies {
         api "com.badlogicgames.gdx:gdx:$gdxVersion"
 
@@ -104,12 +105,13 @@ project(":core") {
         // https://mvnrepository.com/artifact/org.mockito/mockito-junit-jupiter
         testCompile group: 'org.mockito', name: 'mockito-junit-jupiter', version: '3.3.3'
 
-        // https://mvnrepository.com/artifact/org.junit.jupiter/junit-jupiter-engine
-        testCompile group: 'org.junit.jupiter', name: 'junit-jupiter-engine', version: '5.7.0-M1'
-
         // ormlite
         compile group: 'com.j256.ormlite', name: 'ormlite-jdbc', version: '4.48'
         compile 'com.j256.ormlite:ormlite-android:4.48'
         compile 'com.j256.ormlite:ormlite-core:4.48'
+
+        testCompile 'junit:junit:4.12'
+        compile 'junit:junit:4.12'
     }
 }
+

core/src/com/galaxytrucker/galaxytruckerreloaded/Test/Server/Persistence/CrewDAOTest.java

@@ -5,8 +5,8 @@ import com.galaxytrucker.galaxytruckerreloaded.Model.Crew.Crew;
 import com.galaxytrucker.galaxytruckerreloaded.Server.Database.Database;
 import com.galaxytrucker.galaxytruckerreloaded.Server.Persistence.CrewDAO;
 
-import org.junit.jupiter.api.Assertions;
-import org.junit.jupiter.api.Test;
+import org.junit.Assert;
+import org.junit.Test;
 
 import javax.persistence.EntityManager;
 import java.util.UUID;
@@ -39,7 +39,7 @@ public class CrewDAOTest {
         entityManager.getTransaction().begin();
         Crew c2 = entityManager.find(Crew.class, c.getId());
         entityManager.getTransaction().commit();
-        Assertions.assertEquals(c2.getName(), c.getName());
+        Assert.assertEquals(c2.getName(), c.getName());
     }
 
     /**
@@ -62,7 +62,7 @@ public class CrewDAOTest {
         entityManager.getTransaction().begin();
         Crew c2 = entityManager.find(Crew.class, c.getId());
         entityManager.getTransaction().commit();
-        Assertions.assertEquals(c2.getName(), c.getName());
+        Assert.assertEquals(c2.getName(), c.getName());
     }
 
     /**