Wrangler v3 remote default changes credential-free Worker testing

Direct answer

For a credential-free run in Wrangler v3.x, the flag you need is --local. Executing wrangler dev --local forces the local workerd/Miniflare runtime and skips the remote preview, so no Cloudflare login or API token is required. KV bindings are served from a local directory (typically .wrangler/state), and fetch handlers execute inside the local workerd process.

Some v3.x minors also expose a persistence flag such as --local-persistence, but the exact name and behavior vary across patch releases. Treat --local as the stable, version-agnostic guarantee; treat persistence flags as version-dependent until you confirm them against your installed Wrangler.

Confirmed behavior vs. likely divergence

Confirmed: --local runs the Worker locally, emulates KV with a local store, and does not contact the Cloudflare edge API. This makes it safe for CI environments where credentials are intentionally withheld.

Likely divergence: local mode is not a 1:1 mirror of the edge. KV eventual-consistency windows, Cache API semantics, and Queues can behave differently. A green local test suite is necessary but not sufficient for remote correctness.

Asserting binding coverage in tests

Because the runtime injects bindings into the Worker's env object, your test suite can assert coverage by reading each expected binding and failing fast if it is undefined. For KV, add a smoke test that performs put, get, and list against a namespaced test key. This proves the binding is wired and the local store is writable.

// Example smoke test inside the Worker
export default {
  async fetch(request, env) {
    if (!env.MY_KV) throw new Error("KV binding missing");
    await env.MY_KV.put("smoke", "ok");
    const val = await env.MY_KV.get("smoke");
    return new Response(val);
  }
};

Clear the local state before each run to prevent leakage:

rm -rf .wrangler/state

Compatibility boundary and remote-only features

There is no single, static, version-agnostic list that marks every feature as remote-only. The practical boundary is whatever Miniflare/workerd supports locally. As of Wrangler v3.x, Queues and certain Cache API behaviors are commonly reported as diverging or unsupported locally, but the exact set shifts with runtime updates. Features beyond basic KV, fetch, and standard bindings should be treated as requiring a remote integration test or explicit verification against current Cloudflare documentation.

Recommended CI pattern

1. Pin your Wrangler version in CI.
2. Run wrangler dev --local (or the confirmed local flag for that pinned version).
3. Delete .wrangler/state before the test job.
4. Fail the build if any expected binding is absent.
5. Gate a separate remote smoke test behind credentials for features known to diverge locally.

If you share the exact Wrangler v3.x minor version used in your pipeline, I can confirm whether persistence flags are available and which bindings are locally emulated in that release.