test: add two test functions

math/sum_of_digits.cpp

@@ -11,8 +11,17 @@
  * Function to find the sum of the digits of an integer.
  * @param num The integer.
  * @return Sum of the digits of the integer.
+ * 
+ * \detail
+ * First the algorithm check whether the num is negative or positive,
+ * if it is negative, then we neglect the negative sign.
+ * Next, the algorithm extract the last digit of num by dividing by 10 
+ * and extracting the remainder and this is added to the sum.
+ * The number is then divided by 10 to remove the last digit.
+ * This loop continues until num becomes 0. 
  */
 int sum_of_digits(int num) {
+    // If num is negative then negative sign is neglected.
     if (num < 0) {
         num = -1 * num;
     }
@@ -25,17 +34,38 @@ int sum_of_digits(int num) {
 }
 
 /**
- * Test function.
+ * Function for testing the sum_of_digits() function with a
+ * first test case of 119765 and assert statement.
  */
-void test() {
+void test1() {
     int test_case_1 = sum_of_digits(119765);
-    int test_case_2 = sum_of_digits(-12256);
     assert(test_case_1 == 29);
-    assert(test_case_2 == 16);
     }
 
+/**
+ * Function for testing the sum_of_digits() function with a
+ * second test case of -12256 and assert statement.
+ */
+void test2() {
+    int test_case_2 = sum_of_digits(-12256);
+    assert(test_case_2 == 16);
+    }
+/**
+ * Function for testing the sum_of_digits() with 
+ * all the test cases.
+ */
+void test() {
+    //First test.
+    test1();
+    //Second test.
+    test2();
+    }
+
+/**
+ * Main Function
+*/
 int main() {
     test();
-    std::cout << "Success.";
+    std::cout << "Success." << std::endl;
     return 0;
 }