Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the feature has not already been requested

🚀 Feature Proposal

Add a Plugin Testing Guide in Testing.md or Write-plugin.md.

Motivation

Currently, there is no section in either Testing.md or Write-Plugin.md that explains how to test a written plugin. For example, how to test the decorated FastifyRequest, FastifyInstance and FastifyReply. Since we should only include plugins in the ecosystem list containing sufficient tests, we should also provide a guide that explains how to test a plugin.

Example

No response