added test for coprime numbers

test/ggT/test_ggT.c

@@ -55,3 +55,16 @@ void test_ggTOfBoth0(){
     //assert
     TEST_ASSERT_EQUAL_INT(expected,result);
 }
+
+void test_ggTOfCoprimes(){
+    //arrange
+    int a = 13;
+    int b = 27;
+    int expected = 1;
+
+    //act
+    int result = ggT(a,b);
+
+    //assert
+    TEST_ASSERT_EQUAL_INT(expected,result);
+}