update readme with unit test, cfn synthesis test and aws integ test instructions

README.md

@@ -1,20 +1,20 @@
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+</p>
 
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+<p>
+  <a href="https://github.com/sid88in/serverless-appsync-plugin/actions?query=workflow%3ATests"><img alt="Tests" src="https://github.com/sid88in/serverless-appsync-plugin/workflows/Tests/badge.svg"></a>
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+</p>
 
 Deploy [AppSync](https://aws.amazon.com/appsync) API's in minutes using this [Serverless](https://www.serverless.com/) plugin.
 
@@ -80,6 +80,67 @@ appSync:
         tableName: ${sls:stage}-data
 ```
 
+# Testing
+
+The test suite is split into three independent layers. The first two run
+offline and need no AWS account; the third is opt-in and talks to a real AWS
+account.
+
+## Unit tests
+
+Pure logic, schema validation and CloudFormation snapshots under
+`src/__tests__/`. No AWS credentials required.
+
+```bash
+npm test
+
+# Re-run on change
+npm run test:watch
+```
+
+## End-to-end (CloudFormation synthesis) tests
+
+The tests in `e2e/` apply the plugin to the example projects under
+`examples/`, run `serverless package`, and assert on the generated
+CloudFormation. They build the plugin first and **do not deploy anything to
+AWS**, so they need no credentials and are safe to run on every PR. See
+[`e2e/README.md`](e2e/README.md) for details.
+
+```bash
+# Run all synthesis tests (runs `npm run build` first)
+npm run test:e2e
+
+# Unit + e2e together
+npm run test:all
+
+# A single fixture
+npx jest --config jest.e2e.config.ts basic-api-key
+```
+
+## AWS integration tests
+
+The suite in `integration/` exercises the live AWS code paths against a **real
+AWS account**, so it **costs money and requires credentials**. It is gated
+behind `APPSYNC_PLUGIN_INTEGRATION=1` — without it every suite resolves to
+`describe.skip` and the run exits green, which is why it never runs as part of
+`npm test`, `npm run test:e2e`, `npm run test:all`, or the default CI.
+
+```bash
+# Cheapest useful run (evaluate + minimal deploy tiers)
+APPSYNC_PLUGIN_INTEGRATION=1 \
+APPSYNC_PLUGIN_INTEGRATION_REGION=us-west-2 \
+AWS_PROFILE=my-sandbox \
+npm run test:integration
+```
+
+Higher-cost tiers are opt-in on top of the master switch: set
+`APPSYNC_PLUGIN_INTEGRATION_CACHING=1` for the caching tier, and
+`APPSYNC_PLUGIN_INTEGRATION_DOMAIN` + `APPSYNC_PLUGIN_INTEGRATION_HOSTED_ZONE_ID`
+for the custom-domain tier. After a run, sweep any leftover stacks with
+`npm run test:integration:sweep`. See
+[`doc/integration-tests.md`](doc/integration-tests.md) for the full tier
+breakdown, environment variables, and cost profile.
+
 # Configuration
 
 - [General config](doc/general-config.md)