Testing Bindings

Test Worker Loaders the way Devflare expects it to run

Worker Loader bindings let a Worker load additional dynamic Workers at runtime.

Test Worker Loaders by choosing the local harness that matches the product boundary instead of reaching for Cloudflare by default.

The first test should prove application control flow. Escalate to Wrangler remote binding or deployed tests only when the Cloudflare-hosted behavior is the thing under test.

Best for: Dynamic Workers where the app loads Worker code at runtime from an explicit source
Default harness: with explicit Worker payloads or a pure stub
Escalate when: The assertion depends on Cloudflare-hosted product behavior rather than the app calling the binding correctly

Start with the default test loop

Keep the first test small. Name the binding, call the one method your route uses, and assert the behavior your app owns.

When Cloudflare owns the interesting behavior, mark that as a remote/deployed lane instead of building a local fake that claims too much.

Pure test with an explicit Worker stub

import { expect, test } from 'bun:test'

import { createMockWorkerLoader } from 'devflare/test'

test('uses a supplied dynamic Worker stub', async () => {

const loader = createMockWorkerLoader({

stub: {

fetch: async () => new Response('tenant-ok')

}

})

const stub = loader.get('tenant-a', () => ({ mainModule: 'index.js', modules: {} }))

expect(await (await stub.fetch('https://example.com')).text()).toBe('tenant-ok')

})

The helper surface to remember

Use with explicit Worker payloads or a pure stub for config-backed local worker tests.
Use / for pure unit tests.
Use or an explicit integration lane when the test needs Cloudflare credentials or a local Docker/Podman engine.

When to move beyond the default harness

Cloudflare owns dynamic Worker upload, discovery, and hosted lifecycle; local code should pass explicit payloads or stubs.
Do not let a low-fidelity mock become product documentation. Keep mocks framed as application-flow tools.
If a test would mutate paid or remote Cloudflare state, gate it separately from ordinary unit tests.

Local tests should be honest

For Worker Loaders, passing locally means the Devflare contract and app flow are correct. It does not automatically prove every hosted Cloudflare behavior.

Worker Loaders internals

Worker Loaders compiles from to Wrangler , with local/test behavior called out explicitly.

Worker Loaders example

A compact Worker Loaders recipe with config and worker usage in one application path.