Assertion on 'finish' of a Writeable stream

[Sparticuz]

Maybe I don't understand writeable streams, but I can't get this to pass. Error: Test finished without running any assertions It is successfully writing the file to disk. When I can get this to pass, the assertion will be more in-depth for use in CI. I just want to understand why it's not running the assertion. I also tried passing t into the event function (t) => t.pass();, but I got a no-shadow variable error from eslint, and it didn't work.

const test = require("ava");
const fs = require("fs");
const invoice = require("./invoice_payload.json");

test("Make Invoice PDF", async (t) => {
  // Creates a Readable stream
  const invoiceFile = await fillInvoice(invoice[0]);
  const output = fs.createWriteStream("test/filledInvoice.pdf");
  invoiceFile.pipe(output);
  invoiceFile.on("close", () => output.end());
  invoiceFile.on("finish", () => t.pass());
  invoiceFile.on("error", () => t.fail());
});

[sindresorhus]

Your question is about JavaScript, not AVA specifically. The async test function will finish as soon as all the await's are resolved and the following synchronous code executed. The .on handler will never have time to fire. Instead of using .pipe, use stream.pipeline. Something like this:

const test = require("ava");
const fs = require("fs");
const {pipeline: streamPipeline} = require('stream/promises');
const invoice = require("./invoice_payload.json");

test("Make Invoice PDF", async (t) => {
  // Creates a Readable stream
  const invoiceFile = await fillInvoice(invoice[0]);
  const output = fs.createWriteStream("test/filledInvoice.pdf");
  await streamPipeline(invoiceFile, output);
});

[Sparticuz]

Thanks! I think I see why the .on handler wouldn't run. I guess I assumed they would also work similar to a promise. I don't think node 14 has stream/promises, so I had to promisify pipeline, but it looks like it's working now. (I'd want to expand on this example and verify the file get's created with the content I'm looking for, etc..., but at least I'm hitting t.pass() now!)

const test = require("ava");
const { pipeline } = require("stream");
const { promisify } = require("util");
const fs = require("fs");
const invoice = require("./invoice_payload.json");

const pipelinePromise = promisify(pipeline);

test("Make Invoice PDF", async (t) => {
  const filledInvoice = "test/filledInvoice.pdf";
  const invoiceFile = await fillInvoice(invoice[0]);
  const output = fs.createWriteStream(filledInvoice);
  await pipelinePromise(invoiceFile, output);
  t.pass();
});