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Run your mock REST APIs anywhere with Mockoon CLI

Learn how to create mock REST APIs and run them anywhere with the CLI

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Mockoon is a set of free and open-source API mocking tools. They help you get ready to work in no time. Should you be a front-end or back-end developer or a QA tester, Mockoon got you covered with a flexible user interface and a CLI that allows you to bring your mocking scenarios on servers and headless environments.

This tutorial will help you put up on track with the CLI and all its possibilities.

To learn more about APIs and API mocking in general, head over to our API guide or API mocking guide

What is Mockoon CLI?

Mockoon CLI is an NPM package that can run on all environments where Node.js is installed. A Docker image is also available (see Step 8 below).

The CLI is a companion application to Mockoon's main interface designed to receive a Mockoon data file.

It has been written in JavaScript/TypeScript and uses some great libraries like oclif and PM2. One of the benefits of using PM2 is that you can easily manage your running mock APIs through the CLI or by using PM2 commands if you are used to them.

How to use the CLI?

As Mockoon CLI is designed to work in pair with the main user interface, you will learn how to create your first mock API and how to use the mock data with the CLI.

Step 1. Create a mock API using Mockoon interface

One of the prerequisites for using the CLI is to create a mock API in the main application. If you already have a setup in Mockoon, you can jump straight to the next section.

To create a new mock API, we have a Getting started tutorial that will guide you step by step. Once your mock is created, come back to this tutorial to learn how to use it in the CLI.

Step 2. Install the CLI

Before importing your mock API in the CLI, you must install it. First ensure that Node.js is installed on your computer by running node -v in your terminal:

$ node -v v14.15.4

If it's not installed, head over to Node.js' download page and follow the instructions for your operating system.

You are now ready to install the CLI by running the following command npm i -g @mockoon/cli:

$ npm i -g @mockoon/cli + @mockoon/cli[email protected] added 423 packages from 339 contributors in 15s

You can also install Mockoon CLI in the scope of a local project by running npm i @mockoon/cli. You will then need to use npx mockoon-cli ... to run it.

Step 3. Prepare your data file

The CLI can open and migrate data from older versions of Mockoon. However, it doesn't alter the file you provide and only migrates a copy. If you created your mock with a more recent version of the application, you need to update your CLI with the following command: npm install -g @mockoon/cli.

Provide a Mockoon's environment file

You can run your mock in one single step by providing the actual location of your Mockoon environment file. To locate your environment file from the main application, right-click on an environment and select "Show in folder" in the context menu:

show in folder menu entry

Let's pretend your file name is data.json and resides in the current directory.

As an alternative, you can also provide a URL pointing to a Mockoon environment file, and Mockoon CLI will take care of downloading it.

Use an OpenAPI specification file

Another option is to directly pass an OpenAPI specification file. Mockoon supports both JSON and YAML formats in versions 2.0.0 and 3.0.0.

As above, you can provide a path to a local OpenAPI specification file or directly the file's URL.

Step 4. Start you mock API

After locating your environment file, you are ready to run your API mock with the CLI.

In your terminal, navigate to the folder where your Mockoon's data file or OpenAPI file is and run the following command:

mockoon-cli start --data ./data.json


mockoon-cli start --data ./openapi-spec.yaml

If you want to use a remotely hosted files, you can also provide a URL to the --data flag like this:

mockoon-cli start --data https://domain.com/data.json

You can also provide multiple parameters to customize your mock:

  • --pname: to provide a different name for the API mock process. The name will always be prefixed with 'mockoon-'.
  • --port: to override the port on which the mock process will run.

You will find more information regarding the start command, including all the available flags on the official repository.

Step 5. Manage your API mock

After running one or more API server mock, you might want to check their health and statuses. To do so you can type mockoon-cli list:

$ mockoon-cli list Name Id Status Cpu Memory Hostname Port mockoon-test 0 online 0.1 45.6 MB 3000

Mockoon CLI is using PM2, the Node.js process manager, behind the scene. It allows you to use all PM2 usual commands to manage your running mock servers: pm2 list, pm2 kill, etc.

To stop a process, type the following command: mockoon-cli stop {id|name}, where id|name is your process id or name. If you omit the id, you will be prompted to choose a mock to stop. You can also stop all running servers at once with mockoon-cli stop all

Step 6. View a running mock's logs

Mockoon CLI log all events like requests and errors in your user folder in the following files: ~/mockoon-cli/logs/{process_name}-out.log and ~/mockoon-cli/logs/{process_name}-error.log.

The {process_name}-error.log file contains server errors that only occur at startup time and prevent the mock API from running (port in use, etc.).

The {process_name}-out.log file contains all other log entries (all levels) produced by the running mock server. Most of the errors occurring in Mockoon, either the CLI or the main application, are not mission-critical and are considered as "normal" output. As an example, if Mockoon is unable to parse the entering request's JSON body, it will log a JSON parsing error, but it won't block the normal execution of the application.

Step 7. Run as a blocking process

Using the --daemon-off flag will keep the CLI in the foreground. The mock API process will not be managed by PM2. When running as a blocking process, all the logs are sent to both stdout (console) and the usual files.

$ mockoon-cli start -d ./data.json --daemon-off {"level":"info","message":"Server started on port 3000","timestamp":"2022-02-02T14:49:23.367Z"} {"level":"info","message":"GET /test | 200","timestamp":"2022-02-02T14:49:31.286Z"} ...

Step 8. Deploy Mockoon CLI using Docker

Using the generic Docker image published on Docker Hub

A generic Docker image mockoon/cli is automatically built upon each release on Docker Hub's Mockoon CLI repository. It uses a node:14-alpine image and installs the latest version of Mockoon CLI.

All of mockoon-cli start flags (--port, etc.) must be provided when running the container.

To load a data file, you can either mount a local file and pass mockoon-cli start flags at the end of the command:

docker run -d --mount type=bind,source=./data.json,target=/data,readonly -p 3000:3000 mockoon/cli:latest -d data -p 3000

Or directly pass a URL to the mockoon-cli start command:

docker run -d -p 3000:3000 mockoon/cli:latest -d https://raw.githubusercontent.com/mockoon/mock-samples/main/samples/generate-mock-data.json -p 3000

Using the dockerize command

Mockoon CLI also offers a dockerize command which generates a new Dockerfile that will allow you to build a self-contained image. Thus, no Mockoon CLI-specific parameters will be needed at runtime.

Run the dockerize command:

mockoon-cli dockerize --data ./data.json --port 3000 --output ./tmp/Dockerfile

Then, navigate to the tmp folder, where the Dockerfile has been generated, and build the image:

docker build -t mockoon-test .

You can finally run your container:

docker run -d -p <host_port>:3000 mockoon-mock1

Step 9. Use Mockoon CLI in a CI environment: GitHub Actions

Mockoon CLI being a Javascript application, it can run on any environment where Node.js is installed, including continuous integration systems like GitHub Actions or CircleCI. It is useful when you want to run a mock server while running integration tests on another application. For example, you could mock the backend when running a React front-end application tests.

Here is an example of a GitHub Action running a mock API before running some tests:

name: Run mock API server on: push: branches: - main jobs: test: runs-on: ubuntu-latest steps: - uses: actions/[email protected] - name: Use Node.js uses: actions/setup-[email protected] with: node-version: "14.x" - name: NPM install, build and test run: | npm ci npm run build # If mockoon-cli is not a devDependency: # npm install -D mockoon-cli npx mockoon-cli start --data https://domain.com/data.json --port 3000 npm run test