diff --git a/src/Aufgabe1Test.java b/src/Aufgabe1Test.java
index 2e3c0e0..e1001eb 100644
--- a/src/Aufgabe1Test.java
+++ b/src/Aufgabe1Test.java
@@ -1,17 +1,19 @@
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
 
 public class Aufgabe1Test {
 
-    public static void main(String[] args) {
-        //test classes Body and Vector3
-
+    @Test
+    public void testEP2() {
         // create two bodies
-        Body sun = new Body(1.989e30,new Vector3(0,0,0),new Vector3(0,0,0));
-        Body earth = new Body(5.972e24,new Vector3(-1.394555e11,5.103346e10,0),new Vector3(-10308.53,-28169.38,0));
+        Body sun = new Body(SolSystem.SUN);
+        Body earth = new Body(SolSystem.EARTH);
 
-        testValue(earth.distanceTo(sun), 1.4850000175024106E11);
-        testValue(sun.distanceTo(earth), 1.4850000175024106E11);
+        assertEquals(1.4850000175024106E11, earth.distanceTo(sun));
+        assertEquals(1.4850000175024106E11, sun.distanceTo(earth));
 
-        for(int i = 0; i < 3600*24; i++) {
+        for (int i = 0; i < 3600 * 24; i++) {
             Vector3 f1 = earth.gravitationalForce(sun);
             Vector3 f2 = sun.gravitationalForce(earth);
 
@@ -20,36 +22,9 @@ public class Aufgabe1Test {
         }
 
         // a dummy body to check the correct position after 24h of movement
-        Body targetPositionEarth = new Body(1, new Vector3(-1.403250141841815E11,
-                4.859202658875631E10, 0.0), new Vector3(0,0,0));
+        Body targetPositionEarth = new Body(1, new Vector3(-1.403250141841815E11, 4.859202658875631E10, 0.0), new Vector3(0, 0, 0));
 
         // check distance to target position (should be zero)
-        testValue(earth.distanceTo(targetPositionEarth), 0);
-    }
-
-    public static void testComparison(Object first, Object second, boolean expected) {
-        boolean real = first == second;
-
-        if (real == expected) {
-            System.out.println("Successful comparison");
-        } else {
-            System.out.println("Comparison NOT successful! Expected value: " + expected + " / Given value: " + real);
-        }
-    }
-
-    public static void testValue(Object given, Object expected) {
-        if (given == expected) {
-            System.out.println("Successful test");
-        } else {
-            System.out.println("Test NOT successful! Expected value: " + expected + " / Given value: " + given);
-        }
-    }
-
-    public static void testValue(double given, double expected) {
-        if (given < expected + (expected+1)/1e12 && given > expected - (expected+1)/1e12) {
-            System.out.println("Successful test");
-        } else {
-            System.out.println("Test NOT successful! Expected value: " + expected + " / Given value: " + given);
-        }
+        assertEquals(0, earth.distanceTo(targetPositionEarth));
     }
 }
diff --git a/src/Aufgabe2Test.java b/src/Aufgabe2Test.java
index 39b521d..13d2ac1 100644
--- a/src/Aufgabe2Test.java
+++ b/src/Aufgabe2Test.java
@@ -1,78 +1,51 @@
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
 public class Aufgabe2Test {
 
-    public static void main(String[] args) {
-        //test classes BodyQueue and BodyForceMap
-
+    @Test
+    public void testEP2() {
         // create three bodies
-        Body sun = new Body(1.989e30,new Vector3(0,0,0),new Vector3(0,0,0));
-        Body earth = new Body(5.972e24,new Vector3(-1.394555e11,5.103346e10,0),new Vector3(-10308.53,-28169.38,0));
-        Body mercury = new Body(3.301e23,new Vector3(-5.439054e10,9.394878e9,0),new Vector3(-17117.83,-46297.48,-1925.57));
-
+        Body sun = new Body(SolSystem.SUN);
+        Body earth = new Body(SolSystem.EARTH);
+        Body mercury = new Body(SolSystem.MERCURY);
 
         // check basic functions of 'BodyQueue'
-        System.out.println("Test1:");
-
         BodyQueue bq = new BodyQueue(2);
         bq.add(mercury);
         bq.add(sun);
         bq.add(earth);
-        testValue(bq.size(), 3);
+        assertEquals(3, bq.size());
 
-        testValue(bq.poll(), mercury);
-        testValue(bq.poll(), sun);
-        testValue(bq.poll(), earth);
+        assertEquals(mercury, bq.poll());
+        assertEquals(sun, bq.poll());
+        assertEquals(earth, bq.poll());
 
-        testValue(bq.size(), 0);
+        assertEquals(0, bq.size());
 
         bq.add(mercury);
         bq.add(sun);
-        testValue(bq.size(), 2);
+        assertEquals(2, bq.size());
 
         // check constructor of 'BodyQueue'
         BodyQueue bqCopy = new BodyQueue(bq);
-        testComparison(bq, bqCopy, false);
-        testComparison(bq.poll(), bqCopy.poll(), true);
+        assertNotEquals(bq, bqCopy);
+        assertEquals(bqCopy.poll(), bq.poll());
         bq.add(earth);
-        testValue(bq.size(), 2);
-        testValue(bqCopy.size(), 1);
+        assertEquals(2, bq.size());
+        assertEquals(1, bqCopy.size());
 
         // check basic functions of 'BodyForceMap'
-        System.out.println("Test2:");
         BodyForceMap bfm = new BodyForceMap(5);
         bfm.put(earth, earth.gravitationalForce(sun));
         bfm.put(sun, sun.gravitationalForce(earth));
 
-        testValue(bfm.get(earth).distanceTo(earth.gravitationalForce(sun)),0);
-        testValue(bfm.get(sun).distanceTo(sun.gravitationalForce(earth)),0);
+        assertEquals(0, bfm.get(earth).distanceTo(earth.gravitationalForce(sun)));
+        assertEquals(0, bfm.get(sun).distanceTo(sun.gravitationalForce(earth)));
 
-        bfm.put(earth, new Vector3(0,0,0));
-        testValue(bfm.get(earth).distanceTo(new Vector3(0,0,0)), 0);
-        testValue(bfm.get(mercury),null);
-    }
-
-    public static void testComparison(Object first, Object second, boolean expected) {
-        boolean real = first == second;
-
-        if (real == expected) {
-            System.out.println("Successful comparison");
-        } else {
-            System.out.println("Comparison NOT successful! Expected value: " + expected + " / Given value: " + real);
-        }
-    }
-
-    public static void testValue(Object given, Object expected) {
-        if (given == expected) {
-            System.out.println("Successful test");
-        } else {
-            System.out.println("Test NOT successful! Expected value: " + expected + " / Given value: " + given);
-        }
-    }
-
-    public static void testValue(double given, double expected) {
-        if (given < expected + (expected+1)/1e12 && given > expected - (expected+1)/1e12) {
-            System.out.println("Successful test");
-        } else {
-            System.out.println("Test NOT successful! Expected value: " + expected + " / Given value: " + given);
-        }
+        bfm.put(earth, new Vector3(0, 0, 0));
+        assertEquals(0, bfm.get(earth).distanceTo(new Vector3(0, 0, 0)));
+        assertNull(bfm.get(mercury));
     }
 }
diff --git a/src/Aufgabe3Test.java b/src/Aufgabe3Test.java
index 8a3f81f..fb97ed8 100644
--- a/src/Aufgabe3Test.java
+++ b/src/Aufgabe3Test.java
@@ -1,72 +1,67 @@
-import java.util.Objects;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
 
 public class Aufgabe3Test {
 
-    public static void main(String[] args) {
-        //test classes BodyLinkedList and BodyForceTreeMap
-
+    @Test
+    public void testEP2() {
         // create five bodies
-        Body sun = new Body(1.989e30, new Vector3(0, 0, 0), new Vector3(0, 0, 0));
-        Body earth = new Body(5.972e24, new Vector3(-1.394555e11, 5.103346e10, 0), new Vector3(-10308.53, -28169.38, 0));
-        Body mercury = new Body(3.301e23, new Vector3(-5.439054e10, 9.394878e9, 0), new Vector3(-17117.83, -46297.48, -1925.57));
-        Body venus = new Body(4.86747e24, new Vector3(-1.707667e10, 1.066132e11, 2.450232e9), new Vector3(-34446.02, -5567.47, 2181.10));
-        Body mars = new Body(6.41712e23, new Vector3(-1.010178e11, -2.043939e11, -1.591727E9), new Vector3(20651.98, -10186.67, -2302.79));
+        Body sun = new Body(SolSystem.SUN);
+        Body earth = new Body(SolSystem.EARTH);
+        Body mercury = new Body(SolSystem.MERCURY);
+        Body venus = new Body(SolSystem.VENUS);
+        Body mars = new Body(SolSystem.MARS);
 
         // check basic functions of 'BodyLinkedList'
-        System.out.println("Test1:");
-
         BodyLinkedList bl = new BodyLinkedList();
 
         bl.addLast(mercury);
         bl.addLast(sun);
         bl.addLast(earth);
-        testValue(bl.size(), 3);
+        assertEquals(3, bl.size());
 
-        testValue(bl.getFirst(), mercury);
-        testValue(bl.getLast(), earth);
+        assertEquals(mercury, bl.getFirst());
+        assertEquals(earth, bl.getLast());
 
-        testValue(bl.get(0), mercury);
-        testValue(bl.get(1), sun);
-        testValue(bl.get(2), earth);
+        assertEquals(mercury, bl.get(0));
+        assertEquals(sun, bl.get(1));
+        assertEquals(earth, bl.get(2));
 
-        System.out.println("Test2:");
-        testValue(bl.indexOf(earth), 2);
-        testValue(bl.indexOf(sun), 1);
-        testValue(bl.indexOf(mercury), 0);
+        assertEquals(2, bl.indexOf(earth));
+        assertEquals(1, bl.indexOf(sun));
+        assertEquals(0, bl.indexOf(mercury));
 
-        System.out.println("Test3:");
-        testValue(bl.pollFirst(), mercury);
-        testValue(bl.pollLast(), earth);
-        testValue(bl.pollFirst(), sun);
+        assertEquals(mercury, bl.pollFirst());
+        assertEquals(earth, bl.pollLast());
+        assertEquals(sun, bl.pollFirst());
 
-        testValue(bl.size(), 0);
-        testValue(bl.getFirst(), null);
+        assertEquals(0, bl.size());
+        assertNull(bl.getFirst());
 
-        System.out.println("Test4:");
         bl.addFirst(earth);
         bl.addFirst(venus);
         bl.addFirst(sun);
         bl.add(1, mercury);
         bl.add(4, mars);
 
-        testValue(bl.size(), 5);
+        assertEquals(5, bl.size());
 
-        testValue(bl.get(0), sun);
-        testValue(bl.get(1), mercury);
-        testValue(bl.get(2), venus);
-        testValue(bl.get(3), earth);
-        testValue(bl.get(4), mars);
+        assertEquals(sun, bl.get(0));
+        assertEquals(mercury, bl.get(1));
+        assertEquals(venus, bl.get(2));
+        assertEquals(earth, bl.get(3));
+        assertEquals(mars, bl.get(4));
 
         // check constructor of 'BodyLinkedList'
         BodyLinkedList blCopy = new BodyLinkedList(bl);
-        testComparison(bl, blCopy, false);
-        testComparison(bl.pollFirst(), blCopy.pollFirst(), true);
+        assertNotEquals(bl, blCopy);
+        assertEquals(blCopy.pollFirst(), bl.pollFirst());
         bl.addFirst(sun);
-        testValue(bl.size(), 5);
-        testValue(blCopy.size(), 4);
+        assertEquals(5, bl.size());
+        assertEquals(4, blCopy.size());
 
         // check basic functions of 'BodyForceTreeMap'
-        System.out.println("Test5:");
         BodyForceTreeMap bfm = new BodyForceTreeMap();
         bfm.put(earth, earth.gravitationalForce(sun));
         bfm.put(sun, sun.gravitationalForce(earth).plus(sun.gravitationalForce(venus)));
@@ -74,37 +69,11 @@ public class Aufgabe3Test {
         bfm.put(mars, mars.gravitationalForce(sun));
         bfm.put(mercury, mercury.gravitationalForce(sun));
 
-        testValue(bfm.get(earth).distanceTo(earth.gravitationalForce(sun)), 0);
-        testValue(bfm.get(sun).distanceTo(sun.gravitationalForce(earth).plus(sun.gravitationalForce(venus))), 0);
+        assertEquals(0, bfm.get(earth).distanceTo(earth.gravitationalForce(sun)));
+        assertEquals(0, bfm.get(sun).distanceTo(sun.gravitationalForce(earth).plus(sun.gravitationalForce(venus))));
 
-        testValue(bfm.put(earth, new Vector3(0, 0, 0)).distanceTo(earth.gravitationalForce(sun)), 0);
-        testValue(bfm.get(mercury).distanceTo(mercury.gravitationalForce(sun)), 0);
-        testValue(bfm.get(mercury), mercury.gravitationalForce(sun));
-    }
-
-    public static void testComparison(Object first, Object second, boolean expected) {
-        boolean real = first == second;
-
-        if (real == expected) {
-            System.out.println("Successful comparison");
-        } else {
-            System.out.println("Comparison NOT successful! Expected value: " + expected + " / Given value: " + real);
-        }
-    }
-
-    public static void testValue(Object given, Object expected) {
-        if (Objects.equals(given, expected)) {
-            System.out.println("Successful test");
-        } else {
-            System.out.println("Test NOT successful! Expected value: " + expected + " / Given value: " + given);
-        }
-    }
-
-    public static void testValue(double given, double expected) {
-        if (given < expected + (expected + 1) / 1e12 && given > expected - (expected + 1) / 1e12) {
-            System.out.println("Successful test");
-        } else {
-            System.out.println("Test NOT successful! Expected value: " + expected + " / Given value: " + given);
-        }
+        assertEquals(0, bfm.put(earth, new Vector3(0, 0, 0)).distanceTo(earth.gravitationalForce(sun)));
+        assertEquals(0, bfm.get(mercury).distanceTo(mercury.gravitationalForce(sun)));
+        assertEquals(mercury.gravitationalForce(sun), bfm.get(mercury));
     }
 }
diff --git a/src/Body.java b/src/Body.java
index d7b3cc3..69fd084 100644
--- a/src/Body.java
+++ b/src/Body.java
@@ -4,7 +4,7 @@ import codedraw.CodeDraw;
  * This class represents celestial bodies like stars, planets, asteroids, etc...
  */
 public class Body {
-    private double mass;
+    private final double mass;
     private Vector3 massCenter; // position of the mass center.
     private Vector3 currentMovement;
 
@@ -14,6 +14,12 @@ public class Body {
         this.currentMovement = currentMovement;
     }
 
+    public Body(Body other) {
+        this.mass = other.mass;
+        this.massCenter = new Vector3(other.massCenter);
+        this.currentMovement = new Vector3(other.currentMovement);
+    }
+
     /**
      * Returns the distance between the mass centers of this body and the specified body 'b'.
      */
diff --git a/src/SolSystem.java b/src/SolSystem.java
new file mode 100644
index 0000000..972fef7
--- /dev/null
+++ b/src/SolSystem.java
@@ -0,0 +1,7 @@
+public class SolSystem {
+    public static final Body SUN = new Body(1.989e30, new Vector3(0, 0, 0), new Vector3(0, 0, 0));
+    public static final Body EARTH = new Body(5.972e24, new Vector3(-1.394555e11, 5.103346e10, 0), new Vector3(-10308.53, -28169.38, 0));
+    public static final Body MERCURY = new Body(3.301e23, new Vector3(-5.439054e10, 9.394878e9, 0), new Vector3(-17117.83, -46297.48, -1925.57));
+    public static final Body VENUS = new Body(4.86747e24, new Vector3(-1.707667e10, 1.066132e11, 2.450232e9), new Vector3(-34446.02, -5567.47, 2181.10));
+    public static final Body MARS = new Body(6.41712e23, new Vector3(-1.010178e11, -2.043939e11, -1.591727E9), new Vector3(20651.98, -10186.67, -2302.79));
+}
diff --git a/src/SpaceDraw.java b/src/SpaceDraw.java
index 1d31eb2..493d13b 100644
--- a/src/SpaceDraw.java
+++ b/src/SpaceDraw.java
@@ -8,7 +8,6 @@ public class SpaceDraw {
      * where m and r measured in solar units.)
      */
     public static double massToRadius(double mass) {
-
         return Simulation.SUN_RADIUS * (Math.pow(mass / Simulation.SUN_MASS, 0.5));
     }
 
@@ -34,7 +33,6 @@ public class SpaceDraw {
      * Returns the approximate color of temperature 'kelvin'.
      */
     private static Color kelvinToColor(int kelvin) {
-
         double k = kelvin / 100D;
         double red = k <= 66 ? 255 : 329.698727446 * Math.pow(k - 60, -0.1332047592);
         double green = k <= 66 ? 99.4708025861 * Math.log(k) - 161.1195681661 : 288.1221695283 * Math.pow(k - 60, -0.0755148492);
@@ -51,12 +49,15 @@ public class SpaceDraw {
      * A transformation used in the method 'kelvinToColor'.
      */
     private static int limitAndDarken(double color, int kelvin) {
-
         int kelvinNorm = kelvin - 373;
-
-        if (color < 0 || kelvinNorm < 0) return 0;
-        else if (color > 255) return 255;
-        else if (kelvinNorm < 500) return (int) ((color / 256D) * (kelvinNorm / 500D) * 256);
-        else return (int) color;
+        if (color < 0 || kelvinNorm < 0) {
+            return 0;
+        } else if (color > 255) {
+            return 255;
+        } else if (kelvinNorm < 500) {
+            return (int) ((color / 256D) * (kelvinNorm / 500D) * 256);
+        } else {
+            return (int) color;
+        }
     }
 }
diff --git a/src/Vector3.java b/src/Vector3.java
index 2a49656..4788cb8 100644
--- a/src/Vector3.java
+++ b/src/Vector3.java
@@ -22,6 +22,10 @@ public class Vector3 {
         this.z = z;
     }
 
+    public Vector3(Vector3 other) {
+        this(other.x, other.y, other.z);
+    }
+
     /**
      * Returns the sum of this vector and vector 'v'.
      */