Create a testing library for ui-extensions (proof of concept)

Author: kumar303

.prettierrc

@@ -12,6 +12,14 @@
       "options": {
         "printWidth": 50
       }
+    },
+    {
+      "files": [
+        "packages/ui-extensions-tester/**/README.md"
+      ],
+      "options": {
+        "printWidth": 50
+      }
     }
   ]
 }

AGENTS.md

@@ -0,0 +1,12 @@
+# AGENTS.md
+
+After every change, you must:
+
+1. **Run `yarn build`** — rebuild any changed packages.
+2. **Run relevant tests** — ensure all affected test suites pass.
+3. **Check for type errors** — run the TypeScript compiler to verify there are no type errors.
+4. **Check for lint and formatting errors** — run the linter and formatter to ensure code quality.
+
+## Working on ui-extensions-tester
+
+Follow the instructions in [packages/ui-extensions-tester/AGENTS.md](packages/ui-extensions-tester/AGENTS.md).

examples/testing/checkout-basic-testing-example/extensions/checkout-basic-testing-example/dist/checkout-basic-testing-example.js

@@ -0,0 +1,14 @@
+# AGENTS.md
+
+After every change, run the relevant test suites in `examples/testing/*` to verify that example tests still pass.
+
+Keep documentation up to date in both the package README (`packages/ui-extensions-tester/README.md`) and each surface-specific README:
+
+- `packages/ui-extensions-tester/src/admin/README.md`
+- `packages/ui-extensions-tester/src/checkout/README.md`
+- `packages/ui-extensions-tester/src/customer-account/README.md`
+- `packages/ui-extensions-tester/src/point-of-sale/README.md`
+
+Any change to exports, function signatures, or behavior must be reflected in the relevant docs.
+
+Code blocks in README files are formatted at print width 50 via the root `.prettierrc` override. Run `npx prettier --write` on any changed README.