No clear guidance on how to create a mock route context with body

[Skwai]

I'm trying to write tests for a route I've created. However I cannot for the life of me figure out how to set the request.body on createMockContext. The request.body is readonly so clearly it's not intended to be mutated like so:

const ctx = createMockContext()
ctx.request.body = "foo"

I've tried so search the codebase but can't see any examples or interfaces for creating a mocked JSON request context.

[jefgodesky]

createMockContext expects you to pass in the stuff you want in the context as parameters, so you wouldn't create the context and then assign the body; rather, you pass the body in to createMockContext, like this:

const ctx = createMockContext({
   body: 'foo'
})

Except no, that isn't quite right either, because body isn't a string, it's a ReadableStream<any>. So to help with that, I wrote a utility method called stringToReadableStream. But I also favor test-driven development (TDD), which meant writing a test first, so:

import { describe, it } from 'jsr:@std/testing/bdd'
import { expect } from 'jsr:@std/expect'
import stringToReadableStream from './string-to-readable-stream.ts'

describe('stringToReadableStream', () => {
  const greeting = 'Hello, world!'
  const readableStreamToString = async (stream: ReadableStream<any>): Promise<string> => {
    const reader = stream.getReader()
    const decoder = new TextDecoder()
    let result = ''

    while (true) {
      const { done, value } = await reader.read()
      if (done) break
      result += decoder.decode(value, { stream: true })
    }

    result += decoder.decode()
    return result
  }

  it('returns a readable stream', async () => {
    const stream = stringToReadableStream(greeting)
    const back = await readableStreamToString(stream)
    expect(typeof stream).not.toBe('string')
    expect(back).toEqual(greeting)
  })
})

Then...

const stringToReadableStream = (orig: string): ReadableStream<any> => {
  return new ReadableStream({
    start (controller) {
      controller.enqueue(new TextEncoder().encode(orig))
      controller.close()
    }
  })
}

export default stringToReadableStream

At which point you can bring it all together:

import stringToReadableStream from './utils/string-to-readable-stream.ts'

const ctx = createMockContext({
   body: stringToReadableStream('foo')
})

And that works!