The ambiguity of testClient() documentation

[PlayerNguyen]

After searching a documentation for the endpoint testing, I found that the test helper testClient documentation (which kinda depends on hc<...>()) is very ambigous. Since this discussion is created to

• Improve the documentation by extending a test helper documentation
• Better TypeScript-ing support for testClient<...>()

Reason

After looking at the source code, I found that the function testClient<>(app) is returning a unknown type. Although I already tried to put the generic tags onto it.

Examples

Here is my current project

// index.ts
const APIApp = new Hono()

// Main Application
APIApp.get("/test", (c) => c.text("success"));

// API Routes
const routes = APIApp.route("/a", ARouter)
  .route("/b", BRouter)
  

// export type APIAppRoutes = typeof routes;
// export default APIApp;

// endpoint/test.spec.ts
function getTestClientForApiApp() {  // this function is returning unknown type regardless trying to put any generic type into it
  return testClient<APIAppRoutes>(APIApp);
}

[PlayerNguyen]

Additional information

• Using Hono with Bun v1.0.30
• TypeScript (on package.json): 5.0.0
• VSCode, for sure.

[juniorgarcia]

Same was happening to me until I made some tests on how I create my Hono instance.

This works:

// app.spec.ts
import { testClient } from 'hono/testing'
import { Hono } from 'hono'

const app = new Hono().get('/', (c) =>
  c.json({
    message: 'Hello, Hono!',
  }),
)

describe('app', () => {
  it('works', async () => {
    const res = await testClient(app).index.$get()
    expect(await res.json()).toEqual({
      message: 'Hello, Hono!',
    })
  })
})

This does not:

// app.spec.ts
import { testClient } from 'hono/testing'
import { Hono } from 'hono'

const app = new Hono()
app.get('/', (c) =>
  c.json({
    message: 'Hello, Hono!',
  }),
)

describe('app', () => {
  it('works', async () => {
    const res = await testClient(app).index.$get() // Object is of type 'unknown'.ts(2571)
    expect(await res.json()).toEqual({
      message: 'Hello, Hono!',
    })
  })
})

So the problem is being caused by not chaining your routes directly after creating the Hono instance, making impossible for TypeScript to infer the type of the Hono client being created, which might not be the best approach since as far as I know (and I know very little about Hono) this might mess with middlewares since their order matters and some of them might not being applied for every situation.

[thenbe]

So the problem is being caused by not chaining your routes directly after creating the Hono instance

I think you're correct. This section of the docs mention the chaining part explicitly, and also offers an alternative workaround (factory.createHandlers()) that retains type safety.

I still haven't tried this myself yet though as I'm just researching the topic now.