How to Run and Test Azure Functions Locally: A Step-by-Step Guide

Azure Functions enable developers to build event-driven, serverless applications without worrying about infrastructure. While deploying directly to Azure is simple, running and testing Azure Functions locally is a best practice it saves time, reduces deployment errors, and improves code quality.

This article explains why local testing matters, the tools you need, and a step-by-step process to run and test Azure Functions on your local machine.

Why Run Azure Functions Locally?

Running Azure Functions locally helps you:

⚡ Debug code faster without repeated deployments
🧪 Test triggers and bindings before production
💰 Avoid unnecessary Azure costs
🔁 Simulate real-world scenarios and edge cases
🚀 Improve development productivity

Local execution closely mirrors the Azure runtime, making it ideal for development and troubleshooting.

Prerequisites

Before starting, ensure the following tools are installed:

1. Azure Functions Core Tools

This is the local runtime that allows Azure Functions to run on your system.

Install via npm: npm install -g azure-functions-core-tools@4 --unsafe-perm true

2. .NET SDK / Node.js / Python

Install the runtime that matches your function’s language.

.NET Functions → .NET SDK
JavaScript Functions → Node.js (LTS recommended)
Python Functions → Python 3.9+

3. Visual Studio Code (Recommended)

Install these extensions:

Azure Functions
Azure Tools
Azure Storage (optional)

Creating an Azure Function Locally

Step 1: Create a New Function App

Using Azure Functions Core Tools:

func init MyFunctionApp
cd MyFunctionApp

Choose:

Language (C#, JavaScript, Python, etc.)
Worker runtime

Step 2: Create a Function

func new

Select:

Function template (HTTP trigger, Timer trigger, Queue trigger)
Function name
Authorization level (Anonymous / Function)

Running Azure Functions Locally

Step 3: Start the Local Runtime

From your project folder:

func start

You’ll see output like:

Functions:
HttpExample: [GET,POST] http://localhost:7071/api/HttpExample

Your Azure Function is now running locally.

Testing Azure Functions Locally

1. Testing HTTP-Triggered Functions

Use any of the following tools:

Browser

Open the URL shown in the terminal:

http://localhost:7071/api/HttpExample

cURL

curl http://localhost:7071/api/HttpExample?name=Azure

Postman

Method: GET or POST
URL: http://localhost:7071/api/HttpExample
Add headers and request body as needed

2. Testing Non-HTTP Triggers

Timer Trigger

Timer functions run automatically based on CRON expressions. You can modify the schedule to run every few seconds during testing.

Queue / Blob Trigger

Use Azurite, the Azure Storage Emulator:

npm install -g azurite
azurite

Configure local.settings.json to point to Azurite:

{
  "IsEncrypted": false,
  "Values": {
"AzureWebJobsStorage": "UseDevelopmentStorage=true",
  "FUNCTIONS_WORKER_RUNTIME": "dotnet"
  }
}

Debugging Azure Functions Locally

Debugging with Visual Studio Code

Open the function app folder in VS Code
Press F5
Select Attach to Azure Functions
Set breakpoints and debug in real time

This provides full debugging capabilities variable inspection, call stack, and logs.

Managing Configuration with local.settings.json

This file stores environment variables for local development:

{
"Values": {
"MyApiKey": "test-key",
"AzureWebJobsStorage": "UseDevelopmentStorage=true"
}
}

⚠️ Important: Never commit local.settings.json to source control.

Common Issues and Solutions

Issue	Solution
Port already in use	Change port using `func start --port 7072`
Storage errors	Ensure Azurite is running
Runtime mismatch	Confirm SDK version matches Azure runtime
Missing bindings	Check `function.json` configuration

Best Practices for Local Testing

Use Azurite instead of real Azure Storage
Keep configuration environment-specific
Write unit tests alongside function code
Test failure scenarios and timeouts
Log generously using built-in logging tools

Final Thoughts

Running and testing Azure Functions locally is essential for building reliable, scalable, and production-ready serverless applications. With Azure Functions Core Tools, VS Code, and local emulators, developers can replicate cloud behavior efficiently and debug with confidence.

By mastering local execution, you’ll deploy faster, break less, and build smarter serverless solutions.