modified case detections in the main program, created tests

src/TriangleChecker.java

 
   // 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;
+  }
+}

test/TriangleCheckerTest.java

 import static org.junit.Assert.*;
 
 public class TriangleCheckerTest {
-    
+
+    // Arrange
+    float a = 2;
+    float b = 3;
+    float c = 4;
+    float d = - a;
+
+    TriangleChecker.TriangleType none = TriangleChecker.TriangleType.NONE;
+    TriangleChecker.TriangleType normal = TriangleChecker.TriangleType.NORMAL;
+    TriangleChecker.TriangleType isosceles = TriangleChecker.TriangleType.ISOSCELES; // Gleichschenklig
+    TriangleChecker.TriangleType equilateral = TriangleChecker.TriangleType.EQUILATERAL; // Gleichseitig
+
+
     @Test
     public void testValidTriangle() {
 
-        // Arrange
-        float a = 2;
-        float b = 3;
-        float c = 4;
+        assertTrue(TriangleChecker.checkTrianglePossible(a,b,c));
+        assertFalse(TriangleChecker.checkTrianglePossible(0,0,0));
+        assertFalse(TriangleChecker.checkTrianglePossible(0,b,c));
+        assertFalse(TriangleChecker.checkTrianglePossible(a,0,c));
+        assertFalse(TriangleChecker.checkTrianglePossible(a,b,0));
+
+        //combination of falses
+        assertFalse(TriangleChecker.checkTrianglePossible(d,c,c));
+        assertFalse(TriangleChecker.checkTrianglePossible(0,0,c));
+        assertFalse(TriangleChecker.checkTrianglePossible(d,d,d));
+        assertFalse(TriangleChecker.checkTrianglePossible(a,b,0));
+    }
 
-        // Act
-        TriangleChecker.TriangleType type = TriangleChecker.checkTriangle(a, b, c);
+    @Test
+    public void testTriangleType(){
 
-        // Assert
-        assertEquals(TriangleChecker.TriangleType.NORMAL, type);
+        assertEquals(none, TriangleChecker.checkTriangle(a, b, 400));
 
-    }
+        assertEquals(normal, TriangleChecker.checkTriangle(a, b, c));
 
+        assertEquals(isosceles, TriangleChecker.checkTriangle(a, b, b));
+        assertEquals(isosceles, TriangleChecker.checkTriangle(a, a, c/3));
+        assertEquals(isosceles, TriangleChecker.checkTriangle(c, b, c));
+        assertNotEquals(isosceles, TriangleChecker.checkTriangle(a, b, c));
+        assertNotEquals(isosceles, TriangleChecker.checkTriangle(a, a, a));
+
+        assertNotEquals(equilateral, TriangleChecker.checkTriangle(b, a, a));
+        assertEquals(equilateral, TriangleChecker.checkTriangle(a, a, a));
+        assertNotEquals(equilateral, TriangleChecker.checkTriangle(a, b, a));
+        assertNotEquals(equilateral, TriangleChecker.checkTriangle(a, a, b));
+    }
 }