Testing TaskEither from fp-ts using jest: A comprehensive guide

Question

Testing TaskEither from fp-ts using jest: A comprehensive guide

Entering the world of fp-ts, I encounter a function

(path: string) => TaskEither<Erorr, T>

that reads and parses configuration data. Now, my challenge is to create a test for this process.

Here is what I have tried so far:

test('Read config', done => {
  interface Config {
    fld1: string
    fld2: {
      fld: 3
    }
  }

  pipe(
    readConfig<Config>("resources/test-config.toml"),
    TE.fold(
      err => T.of(done(err)),
      toml => T.of(() => {
        expect(toml).toBe({})
        done()
      })
    )
  )

})

However, the test fails due to a timeout issue. Also, there's uncertainty about whether the fold implementation is correct. How can I properly fold from TaskEither to Task and execute it asynchronously?

typescript jestjs fp-ts

Answer 1

Answer №1

Looking for a way to test TaskEither with jest led me to this helpful post:

import * as TE from "fp-ts/lib/TaskEither";
import * as E from "fp-ts/lib/Either";

it("tests TaskEither", async () => {
  const fn = TE.right("something");
  await expect(fn()).resolves.toStrictEqual(E.right("something"));
})

Answer 2

Looking for a way to test TaskEither with jest led me to this helpful post:

import * as TE from "fp-ts/lib/TaskEither";
import * as E from "fp-ts/lib/Either";

it("tests TaskEither", async () => {
  const fn = TE.right("something");
  await expect(fn()).resolves.toStrictEqual(E.right("something"));
})

Answer 3

Answer №2

I forgot to include a function call in my code.

The correct version should have been:

  pipe(
    readConfig<Config>("resources/test-config.toml"),
    TE.fold(
      err => T.of(done(err)),
      toml => T.of(() => {
        expect(toml).toBe({})
        done()
      })
    )
  )()

Answer 4

I forgot to include a function call in my code.

The correct version should have been:

  pipe(
    readConfig<Config>("resources/test-config.toml"),
    TE.fold(
      err => T.of(done(err)),
      toml => T.of(() => {
        expect(toml).toBe({})
        done()
      })
    )
  )()

Testing TaskEither from fp-ts using jest: A comprehensive guide

Answer №1

Answer №2

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