Automating API Mocks in Your CI Pipeline with proxymock

Introduction

When running tests in a CI/CD pipeline, relying on external APIs can introduce instability, slow down execution, and even lead to failed builds due to rate limits or API downtime. Fortunately proxymock provides a solution by capturing API interactions and running a local mock server, enabling fully isolated and repeatable tests.

In this blog, we’ll demonstrate how to integrate proxymock into a GitHub Actions CI pipeline using a demo app called outerspace-go. This app makes calls to the Numbers API and SpaceX API, and we’ll show how proxymock can capture these calls and replay them locally during automated tests.

You can watch the video version of this tutorial on the Speedscale YouTube channel.

Overview of the outerspace-go App

outerspace-go is a Go-based application that fetches data from external APIs:

• The Numbers API provides fun facts about numbers.
• The SpaceX API delivers the latest SpaceX launch data.

By default, running the app will query these APIs directly, but we will configure proxymock to capture and replay these requests for testing purposes.

Why Use proxymock in CI Pipelines?

When running tests in CI/CD, external API dependencies can be problematic:

• Unreliable availability: The API might be down or rate-limited.
• Slow performance: API calls introduce latency into test runs.
• Inconsistent data: Live APIs may return different responses over time.

Using proxymock in CI allows us to:

• Capture real API responses once and replay them consistently.
• Run tests quickly without waiting for network requests.
• Ensure our tests are independent of external services.

Setting Up proxymock Locally

To start using proxymock, install it and record API calls:

Installation

For your MacOS environment it’s as simple as using brew.

brew install speedscale/tap/proxymock

Or download it manually.

Initialize

If this is the first time you’re running you can initialize from your command line:

proxymock init
                         _               _
 ___ _ __   ___  ___  __| |___  ___ __ _| | ___
/ __| '_ \\ / _ \\/ _ \\/ _` / __|/ __/ _` | |/ _ \\
\\__ \\ |_) |  __/  __/ (_| \\__ \\ (_| (_| | |  __/
|___/ .__/ \\___|\\___|\\__,_|___/\\___\\__,_|_|\\___|
    |_|

Welcome to Speedscale! Preparing your installation...
Choose one:
 [1] Need to sign up
 [2] Have an API key
 [3] Have an account but no API key
 [q] Quit
▸ How do you want to initialize the cli? [q]: 1
▸ Enter your email to sign up: 

Recording API Calls

1. Start proxymock in record mode, and make a note of the ID for the snapshot recording that is created.

   proxymock run
   

2. Run the outerspace-go application while proxymock captures the outgoing API requests:

   export http_proxy=http://localhost:4140
   export https_proxy=http://localhost:4140
   go run main.go
   

3. Now run some test transactions against the application and you’ll see some traffic recorded:

   curl <http://localhost:4143/>
   curl <http://localhost:4143/api/numbers>
   curl <http://localhost:4143/api/latest-launch>
   

4. Once you’re done hit CTRL-C on your proxymock window to save your data locally. Now you can open the data in your terminal with this command

   proxymock inspect

proxymock run --dir ./proxymock SNAPSHOT_ID

export http_proxy=http://localhost:4140
export https_proxy=http://localhost:4140

name: CI Pipeline

on: [push, pull_request]

jobs:
  test-and-build-go:
    runs-on: ubuntu-latest
    permissions:
      contents: read
    steps:
    - name: YOUR_STEPS_GO_HERE
    - name: Setup proxymock
      env:
        PROXYMOCK_API_KEY: ${{ secrets.PROXYMOCK_API_KEY }}
      run: make proxymock-setup
    - name: Run proxymock
      run: make proxymock-run
    - name: Run tests with proxymock
      run: make test-with-proxymock