testing_highlighting.md: Add a tip for generating test data

topics/basics/testing_plugins/testing_highlighting.md

@@ -98,3 +98,12 @@ The tag can also have the following optional attributes.
 ```xml
 <warning>warning_highlight<info>warning-and_info_highlight</warning>info_highlight</info>
 ```
+
+### Generating Test Data
+
+To generate an expected highlighting result file for a test:
+
+1. Make sure that Plugin DevKit plugin is installed and [internal mode is enabled](enabling_internal.md).
+2. [Create a Scratch file](https://www.jetbrains.com/help/idea/scratches.html#create-scratch-file) for the tested language.
+3. Write code causing tested highlighting.
+4. Invoke the <ui-path>Tools | Internal Actions | DevKit | Toggle Expected Highlighting Markup</ui-path> action.

topics/tutorials/writing_tests_for_plugins/annotator_test.md

@@ -29,6 +29,8 @@ public class Test {
 }
 ```
 
+> See how to [generate highlighting test data](testing_highlighting.md#generating-test-data).
+
 ## Define a Test Method
 Add the `testAnnotator()` method to the `SimpleCodeInsightTest` class [previously defined](completion_test.md#define-a-test).
 Again, this method configures the test fixture by using the test files.