added check for ISOSCELES

src/Praktikum02/TriangleChecker.java

   public static TriangleType checkTriangle(float a, float b, float c) {
 
     if(a + b > c && a + c > b && b + c > a){
+      if (a == b || b == c || a == c){
+        return TriangleType.ISOSCELES;
+      }
       return TriangleType.NORMAL;
-    } else {
-      return TriangleType.NONE;
     }
+    return TriangleType.NONE;
+
 
 
   }

test/Praktikum02/TriangleCheckerTest.java

     void checkTriangleNone(){
         assertEquals(TriangleChecker.TriangleType.NONE,TriangleChecker.checkTriangle(6,2.9f, 2));
     }
+
+    @Test
+    void checkTriangleISOSCELES(){
+        assertEquals(TriangleChecker.TriangleType.ISOSCELES,TriangleChecker.checkTriangle(6,6, 2));
+    }
 }