new program

src/TriangleChecker.java

 import java.util.Scanner;
 
 public class TriangleChecker {
-  
+
   public enum TriangleType {
-    NONE, 
+    NONE,
     NORMAL,
     ISOSCELES,  // Gleichschenklig
     EQUILATERAL // Gleichseitig
     switch (type) {
       case NONE:
         System.out.println("Kein Dreieck");
-        break;        
+        break;
       case NORMAL:
         System.out.println("Dreieck");
-        break;        
+        break;
       case ISOSCELES:
         System.out.println("Gleichschenkliges Dreieck");
-        break;        
+        break;
       case EQUILATERAL:
         System.out.println("Gleichseitiges Dreieck");
-        break;        
+        break;
     }
   }
 
   // Analyse der Dreiecksart
   public static TriangleType checkTriangle(float a, float b, float c) {
-    return TriangleType.NORMAL;
+
+    if (checkTriangleBasePossibility(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 checkTriangleBasePossibility(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;
+  }
+
+
 }

test/TriangleCheckerTest.java

 import static org.junit.Assert.*;
 
 public class TriangleCheckerTest {
-    
+
     @Test
-    public void testValidTriangle() {
+    public void testIsTriangle() {
 
         // Arrange
-        float a = 7;
-        float b = 3;
-        float c = 1;
+        float a = 3;
+        float b = 2;
+        float c = 4;
 
         // Act
         TriangleChecker.TriangleType type = TriangleChecker.checkTriangle(a, b, c);
         // Assert
         assertEquals(TriangleChecker.TriangleType.NORMAL, type);
 
+        // Arrange
+        a = -2;
+        b = 5;
+        c = 2;
+
+        // Act
+        type = TriangleChecker.checkTriangle(a, b, c);
+
+        // Assert
+        assertEquals(TriangleChecker.TriangleType.NONE, type);
+
+        // Arrange
+        a = 5;
+        b = 5;
+        c = 10;
+
+        // Act
+        type = TriangleChecker.checkTriangle(a, b, c);
+
+        // Assert
+        assertEquals(TriangleChecker.TriangleType.NONE, type);
+    }
+
+    @Test
+    public void testIsoTriangle(){
+        // Arrange
+        float a = 6;
+        float b = 6;
+        float c = 3;
+
+        // Act
+        TriangleChecker.TriangleType type = TriangleChecker.checkTriangle(a, b, c);
+
+        // Assert
+        assertEquals(TriangleChecker.TriangleType.ISOSCELES, type);
+    }
+
+    @Test
+    public void testEqualTriangle(){
+        // Arrange
+        float a = 5;
+        float b = 5;
+        float c = 5;
+
+        // Act
+        TriangleChecker.TriangleType type = TriangleChecker.checkTriangle(a, b, c);
+
+        // Assert
+        assertEquals(TriangleChecker.TriangleType.EQUILATERAL, type);
     }
 
-}
+}