Testing with Images in Javascript

· 444 words · 3 minute read

How to import an image in Javascript to be used in Jest Tests

This article was originally posted on Medium.

How I feel working with Javascript sometimes

The Story 🔗

I was assigned with writing tests using images for an endpoint I created at work. The tests and endpoints were written in Javascript using Jest and Node.js, respectively. I figured it wouldn’t be too difficult — opening a file or image is something I’m familiar with in Java and Python, but the only experience I had doing this in Javascript was when there was a frontend available to pass in the image information. I had some idea of how to do this, so I was determined to figure it out on my own instead of turning to others to get the direct answer. But, as we all know — knowing how to do something in one language doesn’t mean you understand how to do it in another language. I ended up struggling to figure out exactly how to open the image and be able to pass it as a variable and convert it to base64 without acquiring it from a frontend.(Spoiler alert: I ended up asking people)

The Process 🔗

In order to clear up exactly how to do this, I turned to the place (almost) everyone turns to when they have a question: Google.

I executed a total of 31 unique queries. I also ended up asking two separate groups of people for how to do this:

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The Final Solution 🔗

It was a total of two lines of code. Use the method readFileSync and then convert to a base64 string. In code:

var imgFile = readFileSync(pathToImage)
var fileStr = imgFile.toString(“base64”)

For those curious, readFileSync returns a type of type { ext: 'jpg', mime: 'image/jpeg'} which can then be converted to base64.


I hope this article helps you streamline your image working process, and save you 31 unique Google queries.