yMock

What is yMock?

TL;DR: A full-featured management GUI for MSW

yMock is a development tool based on MSW that offers a graphic interface for the developer to manage mock data and a service worker that runs underneath. By using yMock, the developer can see the list of endpoint calls to be intercepted by the worker, change the data each one should return in the response body, and turn on/off the worker interception as a whole or in each endpoint response individually.

It is worth pointing out that, by using the service worker, the interception occurs in the network layer. Therefore the calls are listed and can be inspected in the network tab of your browser's development tools.

What does it do?

• It presents a graphic interface that favors development experience;
• It uses a service worker to intercept API calls in the network layer;
• It lists the URLs registered by MSW to be intercepted;
• It displays and allows the user to override the mocked response;
• It allows the user to start/stop the worker as a whole or in each URL individually.

---

Getting started

Monorepo structure

This project is a monorepo, managed with TurboRepo; here's how it's organized:

ymock
  │
  └── apps
        ├── host
        ├── launcher
        └── ymock
      packages
        └── shared
      docs
      website

• apps, packages: conventional monorepo dirs
• host workspace: the host app (read more later), AKA ymock-host
• ymock workspace: you guessed it, AKA ymock-client
• launcher workspace: yMock's launcher UI, AKA ymock-launcher
• docs workspace: documentation site (WIP)
• website workspace: product website (WIP)
• shared workspace: libraries, utilities, etc

Initializing the monorepo

If it's the first time you use the repo, or if you just cloned it, follow this step; otherwise, skip to the next one.

From the root of the repo, run:

npm i

This will install the deps and register all workspaces to the monorepo manager. Notice that each workspace will have its own node_modules; plus, there'll be a global node_modules at the root of the repo.

Installing & managing deps

As a rule of thumb, use the global installation when you initially clone the repo and if/when you do something that alters the workspace definitions for Turbo (i.e. adding/removing workspaces, or changing the disk location of any workspace -- also see here.).

In all other cases, run per-workspace npm commands with --workspace. For all the details, please refer to this guide.

Running the dev server

Before we start: yMock's use case is to manage a msw instance launched by a host app; the host app could be literally any app run by the end user.

To realistically simulate this behavior, the monorepo contains a host app that imports ymock-launcher as a dependency; the launcher's job is to receive the msw instance and pass it to ymock-client, which lives in a __ymock directory under the host project's root.

flowchart
954045["ymock-launcher dist"] ==>|"is imported by"| 747745["Host project's source files"]
linkStyle 0 stroke:#004aff
688838["msw"] ==>|"is installed to"| 858379["Host project's server"]
linkStyle 1 stroke:#0055ff
798284["ymock-client dist"] ==>|"is installed to"| 385674["/__ymock directory"]
linkStyle 2 stroke:#0021ff
subgraph 747745["Host project's source files"]
end
subgraph 858379["Host project's server"]
385674
end

Loading

So, the global dev task will:

• Run client, launcher & host on their own dev server, in parallel
• Build launcher & client before running dev on the host app
• Import launcher into host as an actual npm dependency, referencing the dist assets
• Copy the client build into host, reproducing how it should work in the context of the end user's project
• Rebuild launcher & client on any dev change, and copy client into host

Ready? Just run -- from the root:

npm run dev

To see yMock in action, click the "Launch yMock" launcher button in the host app.

What if I need to run just one app?

While the global dev command will run the dev task in all workspaces that have one, you can also run it just in some workspaces by using a filter (like --workspace=<WORKSPACE>).

Use the power of the monorepo to your advantage

When you need to rapidly iterate on ymock's UI, just visit ymock-client's dev server -- remember, it's a monorepo, so we're running multiple apps in parallel; in this case, the app won't use an actual reference to msw, but a mock object. The changes you make in dev are instantly reflected in the app.

---

Building

(WIP)