Guides & Tutorials

How to test serverless functions locally

Guides & Tutorials

How to test serverless functions locally

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Yesterday we saw that you could deploy serverless functions by adding your JavaScript, TypeScript or Go files to a specified folder in your project. But how do you develop and test your functions locally so that you can validate that they work correctly before deploying them?

Netlify CLI has the answer in the form of Netlify Dev.

One of the advantages of using Netlify Dev (which comes bundled as part of Netlify CLI), is that it will detect the serverless functions in your project, and automatically serve them for you in a local development server so that they behave just the same as when they are deployed to Netlify.

Simply run netlify dev in your project directory. Your functions will have access to your project's environment variables and be served on the same port as the rest of your web project.

Tip: Install Netlify CLI first by running npm install -g netlify-cli

But there's more!

Netlify CLI can also help you with other tasks related to building serverless functions including testing invocations and creating new functions from a set of boilerplate examples in JavaScript, TypeScript and Go.

Try running netlify functions:create in your project folder and following the prompts.

You can also explore the functions command in Netlify CL by running netlify help functions

# netlify help functions

  functions:build   Build functions locally
  functions:create  Create a new function locally
  functions:invoke  Trigger a function while in netlify dev with simulated data, good for testing function calls including Netlify's Event Triggered Functions
  functions:list    List functions that exist locally
  functions:serve   (Beta) Serve functions locally

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