WIP: Add testing harness

.env.example

@@ -19,6 +19,11 @@ DATABASE_URL=postgresql://${POSTGRES_USER}:${POSTGRES_PASSWORD}@splitpro-db:5432
 # https://next-auth.js.org/configuration/options#secret
 NEXTAUTH_SECRET="secret"
 NEXTAUTH_URL="http://localhost:3000"
+NEXTAUTH_URL_INTERNAL="http://localhost:3000"
+
+# Playwright uses only this disposable database and port.
+E2E_DATABASE_URL="postgresql://postgres:strong-password@localhost:5432/splitpro_test"
+E2E_BASE_URL="http://127.0.0.1:3176"
 
 # The default /home page is a blog page that may not be suitable for your use case.
 # You can change it to /balances or any other URL you want.

.github/copilot-instructions.md

@@ -258,3 +258,14 @@ library/API documentation. This means you should automatically use the Context7
 tools to resolve library id and get library docs without me having to explicitly ask.
 
 Do not generate documentation or tests if not explicitly requested.
+
+## Testing Harness Rules
+
+- Keep fast checks independent from PostgreSQL integration and Chromium E2E jobs.
+- Select unit/component tests with `pnpm test`; select database tests with
+  `pnpm test:integration`; select browser tests with `pnpm exec playwright test --project=chromium`.
+- Integration and E2E commands may only use a disposable local database whose name ends in
+  `_test`. Never run reset, push, or destructive test setup against shared or production data.
+- Read `docs/testing-strategy.md` before changing test selection, CI workflows, or database setup.
+- When browser tests fail, inspect `test-results/e2e` and `playwright-report` artifacts before
+  changing application code.

.github/workflows/test-e2e.yml

@@ -0,0 +1,69 @@
+name: E2E Tests
+
+on:
+  pull_request:
+  push:
+    branches: [main]
+
+permissions:
+  contents: read
+
+jobs:
+  e2e:
+    name: Chromium E2E tests
+    runs-on: ubuntu-latest
+    env:
+      DATABASE_URL: postgresql://splitpro:test-password@localhost:5432/splitpro_harness_test
+      E2E_DATABASE_URL: postgresql://splitpro:test-password@localhost:5432/splitpro_harness_test
+      SKIP_ENV_VALIDATION: '1'
+    services:
+      postgres:
+        image: ossapps/postgres:18.3-trixie
+        env:
+          POSTGRES_USER: splitpro
+          POSTGRES_PASSWORD: test-password
+          POSTGRES_DB: splitpro_harness_test
+        options: >-
+          --health-cmd "pg_isready -U splitpro -d splitpro_harness_test"
+          --health-interval 2s
+          --health-timeout 5s
+          --health-retries 15
+        ports:
+          - 5432:5432
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+
+      - name: Install pnpm
+        uses: pnpm/action-setup@v5
+        with:
+          run_install: false
+
+      - name: Install Node.js
+        uses: actions/setup-node@v6
+        with:
+          node-version: 22.16.0
+          cache: pnpm
+
+      - name: Install dependencies
+        run: pnpm install --frozen-lockfile
+
+      - name: Prepare disposable database
+        run: pnpm exec prisma migrate deploy
+
+      - name: Install Chromium
+        run: pnpm exec playwright install --with-deps chromium
+
+      - name: Run Chromium E2E tests
+        run: pnpm test:e2e -- --project=chromium
+
+      - name: Upload Playwright artifacts on failure
+        if: failure()
+        uses: actions/upload-artifact@v4
+        with:
+          name: playwright-artifacts
+          path: |
+            test-results/e2e
+            playwright-report
+          if-no-files-found: ignore

.github/workflows/test-integration.yml

@@ -0,0 +1,55 @@
+name: Integration Tests
+
+on:
+  pull_request:
+  push:
+    branches: [main]
+
+permissions:
+  contents: read
+
+jobs:
+  integration:
+    name: PostgreSQL integration tests
+    runs-on: ubuntu-latest
+    env:
+      DATABASE_URL: postgresql://splitpro:test-password@localhost:5432/splitpro_harness_test
+      SKIP_ENV_VALIDATION: '1'
+    services:
+      postgres:
+        image: ossapps/postgres:18.3-trixie
+        env:
+          POSTGRES_USER: splitpro
+          POSTGRES_PASSWORD: test-password
+          POSTGRES_DB: splitpro_harness_test
+        options: >-
+          --health-cmd "pg_isready -U splitpro -d splitpro_harness_test"
+          --health-interval 2s
+          --health-timeout 5s
+          --health-retries 15
+        ports:
+          - 5432:5432
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+
+      - name: Install pnpm
+        uses: pnpm/action-setup@v5
+        with:
+          run_install: false
+
+      - name: Install Node.js
+        uses: actions/setup-node@v6
+        with:
+          node-version: 22.16.0
+          cache: pnpm
+
+      - name: Install dependencies
+        run: pnpm install --frozen-lockfile
+
+      - name: Prepare disposable database
+        run: pnpm exec prisma migrate deploy
+
+      - name: Run integration tests
+        run: pnpm test:integration

.gitignore

@@ -7,6 +7,8 @@
 
 # testing
 /coverage
+/test-results
+/playwright/.auth
 
 # database
 /prisma/db.sqlite
@@ -60,4 +62,4 @@ SEED_STATISTICS.md
 
 # Agents
 .worktrees/
-docs/superpowers/
+docs/superpowers/

AGENTS.md

@@ -323,6 +323,33 @@ Husky runs on commit:
 
 Override with `git commit --no-verify` if needed.
 
+## Testing Harness Workflow
+
+Keep the fast checks (`pnpm prettier --check .`, `pnpm lint`, `pnpm tsgo --noEmit`,
+`pnpm test`, and `pnpm build --no-lint`) independent from the disposable database and
+browser jobs. CI runs PostgreSQL integration tests with `pnpm test:integration` and Chromium
+E2E tests with `pnpm exec playwright test --project=chromium` in separate jobs.
+
+### Test Selection
+
+- `pnpm test` selects `src/**/*.{test,spec}.{ts,tsx}` and excludes `src/tests/integration/`.
+- `pnpm test:integration` selects only `src/tests/integration/**/*.{test,spec}.{ts,tsx}`.
+- `pnpm exec playwright test --project=chromium` selects `tests/e2e/` through
+  `playwright.config.ts`; setup runs before the Chromium project.
+- Run one Jest file with `pnpm test src/tests/simplify.test.ts`, one integration file with
+  `pnpm test:integration src/tests/integration/expense.integration.test.ts`, or one browser
+  file with `pnpm exec playwright test tests/e2e/group-expense.spec.ts`.
+
+### Database Safety
+
+Integration and E2E databases must be local/disposable and end in `_test`. The integration
+harness refuses non-local or non-test URLs; never point these commands at development,
+staging, or production data. CI creates a fresh PostgreSQL service and may use
+`prisma db push --accept-data-loss` because that database is disposable. Local worktrees
+must use a separate PostgreSQL container, database name, and host port.
+
+See `docs/testing-strategy.md` for the complete command matrix and agent workflow.
+
 <!-- context7 -->
 
 Use the `ctx7` CLI to fetch current documentation whenever the user asks about a library, framework, SDK, API, CLI tool, or cloud service -- even well-known ones like React, Next.js, Prisma, Express, Tailwind, Django, or Spring Boot. This includes API syntax, configuration, version migration, library-specific debugging, setup instructions, and CLI tool usage. Use even when you think you know the answer -- your training data may not reflect recent changes. Prefer this over web search for library docs.

docker/test/compose.yml

@@ -0,0 +1,22 @@
+name: split-pro-test
+
+services:
+  postgres:
+    image: ossapps/postgres:18.3-trixie
+    container_name: splitpro-testing-harness-db
+    environment:
+      POSTGRES_USER: splitpro
+      POSTGRES_PASSWORD: test-password
+      POSTGRES_DB: splitpro_harness_test
+    command: >-
+      postgres
+      -c shared_preload_libraries=pg_cron
+      -c cron.database_name=splitpro_harness_test
+      -c cron.timezone=UTC
+    ports:
+      - '55439:5432'
+    healthcheck:
+      test: ['CMD-SHELL', 'pg_isready -U splitpro -d splitpro_harness_test']
+      interval: 2s
+      timeout: 5s
+      retries: 15

docs/testing-strategy.md

@@ -0,0 +1,51 @@
+# Testing strategy
+
+SplitPro has three deliberately independent test surfaces. Fast checks fail quickly without
+requiring PostgreSQL; database and browser checks each provision their own disposable service.
+
+## Command matrix
+
+| Purpose              | Exact command                                                             | Selection                                                           |
+| -------------------- | ------------------------------------------------------------------------- | ------------------------------------------------------------------- |
+| Formatting           | `pnpm prettier --check .`                                                 | All supported files                                                 |
+| Lint                 | `pnpm lint`                                                               | Oxlint project sources                                              |
+| Types                | `pnpm tsgo --noEmit`                                                      | TypeScript project                                                  |
+| Unit/component tests | `pnpm test`                                                               | `src/**/*.{test,spec}.{ts,tsx}`, excluding `src/tests/integration/` |
+| One unit file        | `pnpm test src/tests/simplify.test.ts`                                    | The named file                                                      |
+| Integration tests    | `pnpm test:integration`                                                   | `src/tests/integration/**/*.{test,spec}.{ts,tsx}`                   |
+| One integration file | `pnpm test:integration src/tests/integration/expense.integration.test.ts` | The named file                                                      |
+| Chromium E2E         | `pnpm test:e2e -- --project=chromium`                                     | `tests/e2e/`, including setup dependency                            |
+| One E2E file         | `pnpm test:e2e -- tests/e2e/group-expense.spec.ts`                        | The named file                                                      |
+| Production build     | `pnpm build --no-lint`                                                    | Next.js production build                                            |
+
+The pull-request `Check` workflow runs formatting, lint, types, unit/component tests, and the
+build. `Integration Tests` and `E2E Tests` are separate jobs and do not depend on `Check` or on
+each other. E2E failures upload `test-results/e2e` and `playwright-report`.
+
+## Database safety
+
+Integration and E2E tests are destructive by design: they create, update, and delete records.
+Use only a local disposable PostgreSQL database whose database name ends in `_test`. The
+integration harness also requires a local host (`localhost`, `127.0.0.1`, or `::1`) and refuses
+other URLs before tests run. CI creates a new `splitpro_harness_test` service for each job and
+prepares it with:
+
+```bash
+pnpm exec prisma migrate deploy
+```
+
+For local work, copy `.env.example`, use a dedicated container/database/port per worktree, and
+set `DATABASE_URL` (and `E2E_DATABASE_URL` for Playwright) to that `_test` database. Do not use
+`pnpm db:push`, reset, seed, or these test commands against development, staging, or production.
+When the disposable container is no longer needed, stop it with the project’s test-container
+workflow; never clean it by deleting data from a shared server.
+
+## Agent workflow
+
+1. Read this document and the existing harness/configuration before changing tests.
+2. Make the smallest change in the owning packet; keep application, Prisma, Jest, manifest, and
+   lockfile changes out of CI/documentation work.
+3. Run the narrowest affected command first, then `pnpm prettier --check .` and any available
+   fast checks. Run integration/E2E only with a disposable `_test` database.
+4. For E2E failures, preserve and inspect Playwright traces, screenshots, videos, and reports.
+5. Report exact commands and failures; do not weaken selection or database guards to make CI pass.