Message Test
This module provides a tool for developers and themers to generate example Drupal status, warning, and error messages. You can configure the type, number, and length of messages to test how they appear on your site, especially in custom theme layouts. It's useful for ensuring messages are displayed correctly across different areas of your website.
Message test allows you to create lorem ipsum examples of the standard Drupal Status, Warning and Error messages that can be shown to the users.
The type of messages to generate, the number of messages and the length of the messages can be chosen.
Once the options on the form are chosen a redirect URL can be entered and on submit the messages will be generated and the user redirected to the selected URL where the messages will be displayed (unless your theme has changed things).
It is primarily a development/theming tool that allows you to see how the standard Drupal messages will appear on different pages of your site. If you have a vanilla install and do nothing with the standard messaging then it probably is of no use to you but if you change the messages theming or you have pages where the placement is not standard then its useful to be able to generate some test cases.
Post-Installation
After installation go to /admin/config/development/message-test where you will be shown the modules only page. Choose the options as required and click "Generate test messages".
Out of the box the modules functionality is available to anyone with the "Administer site configuration" permission but it also provides a permission "Can test messages" so that any role can use it. Useful for testing message display with roles that use something other than the admin theme.