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CDP

Lab can run tests that use browser-backed FQL, but Lab does not own browser execution or Chrome DevTools Protocol behavior. That belongs to the selected Ferret runtime.

In current Lab v2, there is no --cdp flag and no LAB_CDP environment variable. Configure browser access through the Ferret runtime and FQL options you are using.

Browser-backed tests

A browser-backed test is still a normal Lab test file:

example.fql
read-only
LET doc = DOCUMENT("https://example.com", { driver: "cdp" }) RETURN doc.title

Run it with Lab:

terminal 
lab run browser.fql

If the runtime expects an existing browser endpoint, start that browser separately and make sure the runtime can reach it.

Wait for a browser endpoint

Use --wait when a browser endpoint is started outside Lab and may not be ready yet.

terminal 
lab run browser-tests/ \  --wait=http://127.0.0.1:9222/json/version \  --wait-timeout=5 \  --wait-attempts=12

The wait happens before tests execute. It does not configure the runtime; it only prevents tests from starting before the dependency responds.

Builtin runtime

With the builtin runtime, Ferret runs inside the Lab process. Browser endpoints such as 127.0.0.1:9222 are resolved from the same host where Lab runs.

Use FQL and Ferret runtime configuration for browser driver details. Lab passes user parameters and @lab system parameters into the runtime, but it does not rewrite browser options.

HTTP and binary runtimes

When you use --runtime=http(s)://... or --runtime=bin:..., browser connectivity is evaluated from that runtime’s environment.

For example, if Lab runs on your laptop but the HTTP runtime runs in a container, 127.0.0.1:9222 inside the query refers to the runtime container, not your laptop. Expose or advertise the browser endpoint in a way that the runtime can reach.

The same rule applies to Lab local services. If a remote runtime must fetch @lab.static or @lab.mock URLs, set --serve-bind and --serve-host so those URLs are reachable from the runtime.

For Lab-owned local service flags, see Static File Server and Mock API Server.

CI pattern

A common CI shape is:

  1. Start the browser or runtime service.
  2. Use lab run --wait=... to wait for its health endpoint.
  3. Run tests with --reporter=simple.
terminal 
lab run browser-tests/ \  --wait=http://127.0.0.1:9222/json/version \  --reporter=simple

Next steps

Remote runtime HTTP Runtime Run tests against a remote Ferret HTTP runtime. Local runtime Binary Runtime Run tests through an external Ferret-compatible binary. Test execution Running Tests Run local, HTTP, and Git-hosted test files with parameters and waits.