added simple test for ggT of 2 and 10

test/ggT/test_ggT.c

@@ -0,0 +1,18 @@
+#include "unity.h"
+#include "ggT.h"
+
+void setUp(){}
+void tearDown(){}
+
+void test_ggTOf2And10(){
+    //arrange
+    int a = 2;
+    int b = 10;
+    int expected = 5;
+
+    //act
+    int result = ggT(a,b);
+
+    //assert
+    TEST_ASSERT_EQUAL_STRING(expected, result);
+}