modified case detections in the main program, created tests

src/TriangleChecker.java

@@ -47,8 +47,23 @@ public class TriangleChecker {
 
   // Analyse der Dreiecksart
   public static TriangleType checkTriangle(float a, float b, float c) {
+    if(checkTrianglePossible(a, b, c)) {
+        if (a == b && a == c) {
+          return TriangleType.EQUILATERAL;
+        }
+        if (a == b || a == c || b == c) {
+          return TriangleType.ISOSCELES;
+        }
+        return TriangleType.NORMAL;
+      }
     return TriangleType.NONE;
   }
 
 
-}
+  public static boolean checkTrianglePossible(float a, float b, float c){
+    if(a <= 0 || b <= 0 || c <= 0){
+      return false;
+    }
+    return a+b > c && a + c > b && b + c > a;
+  }
+}