added test for converting small int to hex string

test/conversionOfNumbers/test_conversionOfNumbers.c

@@ -115,3 +115,16 @@ void test_convertBinaryStr1001ToInt9(){
     //assert
     TEST_ASSERT_EQUAL_UINT(expected, result);
 }
+
+void test_convert3ToHexStr3(){
+    //arrange
+    char* result;
+    char expected[] = "3";
+
+    //act
+    result = convertIntToHex(3);
+
+    //assert
+    TEST_ASSERT_EQUAL_STRING(expected, result);
+    free(result);
+}