docs: add canonical Cypress/Clerk testing guide

README.md

@@ -131,6 +131,8 @@ Open http://localhost:3000.
 
 ## Common commands
 
+- Testing notes: [`docs/testing/README.md`](./docs/testing/README.md)
+
 ### Coverage policy
 
 CI enforces a **scoped 100% coverage gate** (statements + branches) for a small set of unit-testable modules.

docs/testing/README.md

@@ -0,0 +1,86 @@
+# Testing
+
+This repo uses a mix of unit tests and Cypress end-to-end (E2E) tests.
+
+## Cypress E2E: conventions (stories)
+
+Write E2E tests as **user stories** describing what a user does (and does not do):
+
+- Prefer descriptive spec names like:
+  - `As a signed-in user, I can view my activity feed (happy path)`
+  - `As a signed-out user, I get redirected to sign-in (negative path)`
+  - `As a user, invalid API URL shows an error state (negative path)`
+- Include **both**:
+  - **Positive/happy path** (expected successful flow)
+  - **Negative paths** (missing inputs, unauthenticated access, invalid states)
+
+Keep each spec focused on one story/flow; avoid long “mega specs”.
+
+## Cypress E2E: Clerk auth (official implementation)
+
+Hard requirements:
+- **No auth bypass** in E2E.
+- Use Clerk’s **official Cypress support** via `@clerk/testing`.
+
+Implementation in this repo:
+- `frontend/cypress.config.ts` calls `clerkSetup()`.
+- `frontend/cypress/support/e2e.ts` imports and registers commands:
+  - `addClerkCommands({ Cypress, cy })`
+- Tests can use:
+  - `cy.clerkLoaded()`
+  - `cy.clerkSignIn(...)` / `cy.clerkSignOut(...)`
+
+See also: [`docs/e2e-auth.md`](../e2e-auth.md).
+
+### Test user (non-secret)
+
+- Email: `jane+clerk_test@example.com`
+- OTP: `424242`
+
+## Required environment variables
+
+### Local E2E (running Cypress yourself)
+
+You typically need:
+
+- `NEXT_PUBLIC_API_URL` (required)
+  - Must be reachable from the **browser** (host), not just from inside Docker.
+  - Examples:
+    - Local backend: `http://localhost:8000`
+    - CI E2E job (frontend dev server): `http://localhost:3000` (see workflow)
+
+- Clerk env (values should come from your Clerk app; **do not commit secrets**):
+  - `NEXT_PUBLIC_CLERK_PUBLISHABLE_KEY` (required for the app)
+  - `CLERK_SECRET_KEY` (required for Clerk testing tokens)
+
+- Cypress Clerk test user identifier (non-secret, repo default is OK):
+  - `CYPRESS_CLERK_TEST_EMAIL` (defaults to `jane+clerk_test@example.com` in CI)
+
+Note: Cypress automatically maps `CYPRESS_FOO=bar` into `Cypress.env('FOO')`.
+
+### CI artifacts on E2E failures (required)
+
+For E2E failures, always upload Cypress artifacts so failures are debuggable from CI:
+
+- `frontend/cypress/screenshots/**`
+- `frontend/cypress/videos/**`
+
+(Our GitHub Actions workflow already uploads these as an artifact for every E2E run.)
+
+## Running Cypress locally
+
+From repo root:
+
+```bash
+make frontend-sync
+
+# in one terminal
+cd frontend
+npm run dev -- --hostname 0.0.0.0 --port 3000
+
+# in another terminal
+cd frontend
+npm run e2e -- --browser chrome
+```
+
+If you hit Clerk-related bot detection or sign-in failures, re-check the Clerk testing env vars above.