Work out a testing/mocking story

[aturon]

At the moment, it's not clear how to test a Tide application. Ideally we can build on best practices in the Rust ecosystem, including the stories worked out in other frameworks like Rocket.

[skade]

We kind of already have those best practices: http::Request and http::Response can be easily produced without a web server at hand and the application called with that. We can make assertions on those.

What's missing is a testing framework based on http that eases the process and maybe provides custom matchers. This one doesn't have to be Tide-specific.
Also, we don't yet have a good definition of where we want people to plug a test in. (e.g.: is an Endpoint testable?)

I'd be interested in working on that a little.

[tomhoule]

I am currently working on a session middleware implementation, and it would be helpful to be able to test that way (given a tide::App, an async function from http::Request to http::Response). With http_service, as far as I can see, we could have something very close by making App::into_server and Server public. Would that be desirable? (I can open a PR if we want this).

edit: apparently #140 does exactly that.

[tirr-c]

cc #15, App-level testing is tracked there.