added test for both numbers 0

test/ggT/test_ggT.c

@@ -42,3 +42,16 @@ void test_ggTOfPositiveAnd0(){
     //assert
     TEST_ASSERT_EQUAL_INT(expected, result);
 }
+
+void test_ggTOfBoth0(){
+    //arrange
+    int a = 0;
+    int b = 0;
+    int expected = 0;
+
+    //act
+    int result = ggT(a,b);
+
+    //assert
+    TEST_ASSERT_EQUAL_INT(expected,result);
+}