Add testing utilities

[MickL]

Describe the feature

At least missing:

• Setup Nitro app
• Provide fetch function
• Mock utils

Something like this: https://github.com/johannschopplich/nitro-starter/blob/main/test/utils.ts

Additional information

• Would you be willing to help implement this feature?

[pi0]

~> #2303

[MickL]

@pi0 Does this mean all tools for testing are existing but not documented?

• Is there a function to setup the Nitro app for tests?
• Are there fetch functions?
• How can I mock something like database connection or auth sessions?

The first two I currently implemented myself by looking at this repository: https://github.com/johannschopplich/nitro-starter/tree/main/test thanks to @johannschopplich

[pi0]

I have a plan to work on a branding new testing system for Nitro server which i need to better explain later once more shaped idea but in the meantime any setup that works for you. Setup function in shared repo seems nice 👍🏼

[MickL]

Sounds good! Possibly for v3?

[johannschopplich]

For the record: I've built nitro-test-utils until the official utilities are ready. 🙂