Add missing new line

Co-authored-by: Akhil G Krishnan <[email protected]>

guides/source/testing.md

@@ -477,6 +477,7 @@ Known extensions: rails, pride
 ```
 
 #### Filtering Tests
+
 The `--name` (`-n`) and `--exclude` options can be used to filter (include or exclude) tests based on the test name, not the file name. Test names are derived from the standard Ruby nomenclature of Class::Module::method. To name the tests, the Minitest DSL replaces `::` with `#` and converts test names to methods using snake_case and the prefix `test_` (preserving case). For example:
 
 ```