Fix mention of MSTest ordering tests (#42297)

Co-authored-by: Jakub Jareš <[email protected]>

Author: Evangelink

docs/core/testing/order-unit-tests.md

@@ -20,7 +20,11 @@ If you prefer to browse the source code, see the [order .NET Core unit tests](/s
 
 ## Order alphabetically
 
-With MSTest, tests are automatically ordered by their test name.
+MSTest discovers tests in the same order in which they are defined in the test class.
+
+When running through Test Explorer (in Visual Studio, or in Visual Studio Code), the tests are ordered in alphabetical order based on their test name.
+
+When running outside of Test Explorer, tests are executed in the order in which they are defined in the test class.
 
 > [!NOTE]
 > A test named `Test14` will run before `Test2` even though the number  `2` is less than `14`. This is because test name ordering uses the text name of the test.