feat: add Hono test client (RPC)

[hagishi]

Author should do the followings, if applicable

• Add tests
• Run tests
• yarn denoify to generate files for Deno

What this PR do?

By using the hc test client, we can easily write tests. This utility enables efficient integration and unit testing by allowing manipulation of the Hono application object rather than making actual HTTP requests.

Usage Example

it('test', async() => {
  const app = new Hono().get('/search', (c) => c.jsonT({ hello: 'world' }))
  const res = await hc(app).search.$get()

  expect(await res.json()).toEqual({ hello: 'world' })
})

[yusukebe]

Hi @hagishi!

Cool! This is one of the things we want to do with RPC-mode. Introducing the testing helper makes sense.

But, there's one thing we should consider. The function name hc might be confusing because hono/client has a function with the same name. I haven't come up with a perfect name yet, but something like appToClient() might be better. Any thoughts?

[hagishi]

Hi @yusukebe,

Thank you for the review.

I agree that some parts could indeed be confusing.
Following the example of frameworks like FastAPI,
I think a clearer naming convention like testClient(app) would be better.
What do you think?"

[yusukebe]

Hi @hagishi !

testClient is simple and good! Let's go with it.

[yusukebe]

Hi @hagishi

Thanks! Merging it now.