mock-npm-registry

This internal package can be used in tests by othe packages to set up a mock local npm registry, publish locally built copies of the packages and their dependencies, then install those packages into test fixtures.

Usage

A good example is the vitest-pool-workers e2e tests. See packages/vitest-pool-workers/test/global-setup.ts

export default async function ({ provide }: GlobalSetupContext) {
	const stop = await startMockNpmRegistry("@cloudflare/vitest-pool-workers");

	// Create temporary directory
	const projectPath = await createTestProject();
	execSync("pnpm install", { cwd: projectPath, stdio: "ignore" });

	provide("tmpPoolInstallationPath", projectPath);

Here you can see that in Vitest global setup file, we are calling startMockNpmRegistry(). We pass in the @cloudflare/vitest-pool-workers package name, which will ensure that this package (and all its local dependencies, such as Wrangler, Miniflare, etc) is built and published to the mock registry.

We then create a temporary test project that has a dependency on @cloudflare/vitest-pool-workers and then run pnpm install, which will install the locally published packages.

The path to this temporary test project is provided to tests.

Debugging

If you are having problems with the mock npm registry, you can get additional debug logging by setting the NODE_DEBUG environment variable.

NODE_DEBUG=mock-npm-registry

Source: packages/mock-npm-registry/README.md