added test for converting into hex for numbers smaller than 16

test/conversionOfNumbers/test_conversionOfNumbers.c

@@ -124,6 +124,19 @@ void test_convert3ToHexStr3(){
     //act
     result = convertIntToHex(3);
 
+    //assert
+    TEST_ASSERT_EQUAL_STRING(expected, result);
+    free(result);
+}
+
+void test_convert12ToHexStrC(){
+    //arrange
+    char* result;
+    char expected[] = "C";
+
+    //act
+    result = convertIntToHex(12);
+
     //assert
     TEST_ASSERT_EQUAL_STRING(expected, result);
     free(result);