review: rb: develop comments and add some details

Add some comments about rbtree to make it more readable
Add more detail infos to make the purpose and process
of the test cases more clear which include test goal,
test step, input, judging criteria, constraints, etc.,
and these can be seen in our Zephyr documentations.

Signed-off-by: Ningx Zhao <ningx.zhao@intel.com>

tests/benchmarks/data_structure_perf/rbtree_perf/src/rbtree_perf.c

@@ -31,14 +31,41 @@ bool node_lessthan(struct rbnode *a, struct rbnode *b)
  * @brief Test whether rbtree node struct is embedded
  * in any user struct
  *
- * @details Initialize a user defined structure contains
- * rbtree node.And into a rbtree and enumerate
- * the rbtree nodes.
+ * @details
+ * Test Objective:
+ * - Define and initialize a rbtree, and test two features:
+ * first, rbtree node struct can be embeded in any user struct.
+ * last, rbtree can be walked though by some macro APIs.
  *
- * verify that the value enumerated is equal to the
- * value initialized.If the verification pass,the user
- * defined structure works.
- * verify "for each" style APIs work.
+ * Testing techniques:
+ * - Interface testing
+ * - Dynamic analysis and testing
+ * - Structural test coverage(entry points,statements,branches)
+ *
+ * Prerequisite Conditions:
+ * - Design a predicate function node_lessthan
+ * - Define a rbtree by using struct rbtree
+ *
+ * Input Specifications:
+ * - N/A
+ *
+ * Test Procedure:
+ * -# Define some arrays of rbtree nodes.And initialize
+ * the rbtree.
+ * -# Then inserting some nodes into the rbtree.
+ * -# Check if the inserted nodes are contained in the
+ * rbtree by using the iteration APIs.
+ *
+ * Expected Test Result:
+ * - The inserted nodes are contained in the
+ * rbtree by using the iteration APIs.
+ *
+ * Pass/Fail Criteria:
+ * - Successful if check points in test procedure are all pass,
+ * otherwise failure.
+ *
+ * Assumptions and Constraints:
+ * - N/A
  *
  * @ingroup lib_rbtree_tests
  *
@@ -117,15 +144,47 @@ void verify_rbtree_perf(struct rbnode *root, struct rbnode *test)
  * logarithmic time
  *
  * @details
- * Defining a rbtree and then searching height of maximum(minimum)
- * node(searched,inserted or removed),and finally record those heights.
+ * Test Objective:
+ * - The inserted, removed, get minimum and get maximum operations
+ * of rbtree are in logarithmic time by comparing a node's operation
+ * height with the worst-case's height.
  *
- * verify that search heights are less than the height of
- * worset-case condition(<= 2lg(N)).(N is the size of tree)
+ * Testing techniques:
+ * - Interface testing
+ * - Dynamic analysis and testing
+ * - Structural test coverage(entry points,statements,branches)
+ *
+ * Prerequisite Conditions:
+ * - Design a predicate function node_lessthan
+ * - Define a rbtree by using struct rbtree
+ *
+ * Input Specifications:
+ * - N/A
+ *
+ * Test Procedure:
+ * -# Initialize the rbtree and insert some nodes on it.
+ * -# Search the far left/right node by recursion and
+ * record its height.
+ * -# Check if the recorded heights are less than the worst
+ * case height(log2(N)).
+ * -# Select out a node at the rbtree arbitrarily as remove
+ * and insert node. And record the height.
+ * -# repeat the check point above.
+ *
+ * Expected Test Result:
+ * - Some operations of rbtree are running in
+ * logarithmic time
+ *
+ * Pass/Fail Criteria:
+ * - Successful if check points in test procedure are all pass,
+ * otherwise failure.
+ *
+ * Assumptions and Constraints:
+ * - N/A
  *
  * @ingroup lib_rbtree_tests
  *
- * @see rb_get_min(),rb_get_max()
+ * @see rb_get_min(), rb_get_max()
  */
 void test_rbtree_perf(void)
 {