Tests randomly return bad XRef Entry after readFileSync

Question

This is probably too specific but I can't find what is wrong with this.

I'm using cypress test tool and I need to verify the contents of a PDF. For this I've created a task:

const pdf = require('pdf-parse');

getPdfContent(pdfName) {
 return pdf(fs.readFileSync('cypress/downloads/' + pdfName))
}

On my test I call

 cy.task("getPdfContent", "Test PDF File.pdf").then(content => {
  expect(content.text).to.have.string("Testing content")
 })

Sometimes the test passes like a charm, but sometimes I get the error bad XRef Entry. For what I have read this is a problem with the PDF file but the PDF file I download is fine. Furthermore if I rerun the same process with the same file, it works fine.

So it looks like the problem is what readFileSync is passing to the pdf() function. My theory is that the process is not finished when pdf() wants to parse it, as it only happens sometimes.

But I can't figure out what is going on. Could it be that readFileSync is not working correctly everytime?

Is there a way to verify or wait for it to finish before calling pdf() on it?

Answer 1

It's unlikely fs.readFileSync() is returning too early.

Since you are picking your file from the downloads folder, it may be that the download is still progressing when you attempt to read it.

To check it out, temporarily add a cy.wait() for a period longer than the download period (or experiment if that's unknown).

Try placing a kosha file in downloads and burn test your task to see if it is stable with a known-good file.

Lastly, there's a try-catch example here Check if file is corrupted with node.js that you could add to the task code.