fix: Clean up of code examples in CONTRIBUTING to follow guidelines. (#1063)

CONTRIBUTING.md

@@ -67,10 +67,10 @@ namespace name {
 /**
  * Class documentation
  */
-class cls_name{
+class class_name {
  private:
-    int var1;  ///< short info of this variable
-    char *msg;  ///< short info
+    int variable;  ///< short info of this variable
+    char *message;  ///< short info
 
  public:
     // other members also documented as below
@@ -87,15 +87,16 @@ class cls_name{
 template<class T>
 bool func(int param1, T param2) {
     // function statements here
-    if(/*something bad*/)
+    if (/*something bad*/) {
         return false;
+    }
 
     return true;
 }
 
 /** Test function */
-void test() {
- /* some statements */
+static void test() {
+    /* desciptions of the following test */
     assert(func(...) == ...); // this ensures that the algorithm works as expected
 
     // can have multiple checks
@@ -103,6 +104,7 @@ void test() {
 
 /** Main function */
 int main(int argc, char *argv[]) {
+    test(); // execute the tests
     // code here
     return 0;
 }