Improve the documentation.

Add demo code for cv::reduce, cv::merge and cv::split.

modules/ts/include/opencv2/ts.hpp

@@ -392,14 +392,14 @@ public:
         FAIL_MEMORY_CORRUPTION_BEGIN=-7,
         FAIL_MEMORY_CORRUPTION_END=-8,
 
-        // the tested function (or test ifself) do not deallocate some memory
+        // the tested function (or test itself) do not deallocate some memory
         FAIL_MEMORY_LEAK=-9,
 
         // the tested function returned invalid object, e.g. matrix, containing NaNs,
         // structure with NULL or out-of-range fields (while it should not)
         FAIL_INVALID_OUTPUT=-10,
 
-        // the tested function returned valid object, but it does not match to
+        // the tested function returned valid object, but it does not match
         // the original (or produced by the test) object
         FAIL_MISMATCH=-11,
 
@@ -407,7 +407,7 @@ public:
         // but it differs too much from the original (or produced by the test) object
         FAIL_BAD_ACCURACY=-12,
 
-        // the tested function hung. Sometimes, can be determined by unexpectedly long
+        // the tested function hung. Sometimes, it can be determined by unexpectedly long
         // processing time (in this case there should be possibility to interrupt such a function
         FAIL_HANG=-13,
 
@@ -448,7 +448,7 @@ public:
     std::vector<std::string> data_search_subdir;
 protected:
 
-    // these are allocated within a test to try keep them valid in case of stack corruption
+    // these are allocated within a test to try to keep them valid in case of stack corruption
     RNG rng;
 
     // information about the current test