Update tests/README.md re new Structures unit tests

Author: delphidabbler

Diff for: tests/README.md

@@ -35,6 +35,10 @@ Contains the _TestCatMaths_[^2] project that provides _DUnit_ tests for selected
 
 ### `./Cat-String`
 
+Contains the _TestCatStructsXE_[^3] project that provides _DUnit_ tests for selected snippets from the database's _Structures_ category.
+
+### `./Cat-Structs`
+
 Contains the _TestCatString_[^2] project that provides _DUnit_ tests for selected snippets from the database's _String Management_ category.
 
 ### `./Cat-WinSys`
@@ -47,6 +51,8 @@ These test files originated as a [zip file on Google Drive](https://drive.google
 
 All subsequent changes to the files were made on GitHub. At present the GitHub repository differs from the original code on Google Drive.
 
-[^1]: There are different versions of the group project file for different Delphi versions: `CodeSnippetsTestsbdsgroup` for Delphi 2006, `CodeSnippetsTests.groupproj` for Delphi 2007-2010 and `CodeSnippetsTestsXE.groupproj` for Delphi XE.
+[^1]: There are different versions of the group project file for different Delphi versions: `CodeSnippetsTests.bdsgroup` for Delphi 2006, `CodeSnippetsTests.groupproj` for Delphi 2007-2010 and `CodeSnippetsTestsXE.groupproj` for Delphi XE.
+
+[^2]: There are different versions of project files for different Delphi versions. They are one or more of `<NAME>.bdsproj` for Delphi 2006, `<NAME>.dproj` for Delphi 2007 to 2010 and `<NAME>XE.dproj` for Delphi XE,  where `<NAME>` is the base name of the project, for example `TestDateCat` or `TestCatMaths`. There are also different `.dpr` files: `<NAME>.dpr` for compilers earlier than Delphi XE and `<NAME>XE.dpr` for Delphi XE.
 
-[^2]: There are different versions of project files for different Delphi versions. They are one or more of `<NAME>.bdsproj` for Delphi 2006, `<NAME>.dproj` for Delphi 2007 to 2010 and `<NAME>XE.dproj` for Delphi XE,  where `<NAME>` is the base name of the project, for example `TestDateCat` or `TestCatMaths`.
+[^3]: There is only one project file for the _Structures_ category tests, `TesttCatStructsXE.dpr`, which is targetted at Delphi XE. There is no test project targetted at earlier compilers. This project is only included in the `CodeSnippetsTestsXE.groupproj` group and no others.