Add CI that checks the demo handles an injected DynamoDB fault

.github/workflows/main.yml

@@ -0,0 +1,51 @@
+name: Run on LocalStack
+
+on:
+  push:
+    paths-ignore:
+      - 'README.md'
+    branches:
+      - master
+  pull_request:
+    branches:
+      - master
+  workflow_dispatch:
+
+jobs:
+  chaos:
+    name: Run the chaos demo
+    runs-on: ubuntu-latest
+    timeout-minutes: 20
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 22
+
+      - name: Setup .NET
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: '9.0.x'
+
+      - name: Install lstk
+        run: |
+          npm install -g @localstack/lstk
+          lstk setup aws --force --non-interactive
+
+      - name: Build the demo
+        run: dotnet build ChaosEngDemo
+
+      - name: Start LocalStack
+        env:
+          LOCALSTACK_AUTH_TOKEN: ${{ secrets.LOCALSTACK_AUTH_TOKEN }}
+        run: lstk start
+
+      - name: Run tests
+        run: make test
+
+      - name: Show LocalStack logs
+        if: failure()
+        run: lstk logs | tail -200

Makefile

@@ -21,6 +21,9 @@ logs:		## Save the logs in a separate file
 	@lstk logs > logs.txt
 
 run:		## Run the chaos demo
-	dotnet run
+	dotnet run --project ChaosEngDemo
 
-.PHONY: usage install start stop logs run
+test:		## Run the demo with and without a DynamoDB fault injected
+	./test.sh
+
+.PHONY: usage install start stop logs run test

README.md

@@ -29,6 +29,8 @@ make start
     * Retrieve the item and print its attributes to the console.
     * Handle any exceptions that may occur during these operations.
 
+3. **Test the error handling:** `make test` runs the demo twice. The first run has a fault injected on DynamoDB `PutItem` through the [LocalStack Chaos API](https://docs.localstack.cloud/aws/capabilities/chaos-engineering/chaos-api/), so the program reports the `AccessDeniedException`. The second run has no fault and reads the item back.
+
 ## Key Concepts
 
 * **LocalStack:**  Provides a local AWS cloud stack for development and testing.  This allows you to run the demo without needing a real AWS account.

test.sh

@@ -0,0 +1,52 @@
+#!/bin/bash
+# Run the demo twice:
+# 1. with a fault injected on DynamoDB PutItem through the LocalStack Chaos API,
+#    and check the program reports the AWS SDK exception
+# 2. without the fault, and check the item is stored and read back
+set -euo pipefail
+
+ENDPOINT=${ENDPOINT:-http://localhost:4566}
+RUN_DEMO=${RUN_DEMO:-dotnet run --project ChaosEngDemo}
+# A non-retryable error, so the SDK fails fast instead of backing off
+FAULT='[{"service": "dynamodb", "region": "us-east-1", "operation": "PutItem", "probability": 1.0,
+  "error": {"statusCode": 400, "code": "AccessDeniedException"}}]'
+
+remove_fault() {
+  curl -s -X DELETE "$ENDPOINT/_localstack/chaos/faults" -H 'Content-Type: application/json' -d "$FAULT" > /dev/null
+}
+trap remove_fault EXIT
+
+echo "Injecting a fault on DynamoDB PutItem"
+curl -s --fail-with-body -X POST "$ENDPOINT/_localstack/chaos/faults" \
+  -H 'Content-Type: application/json' -d "$FAULT" > /dev/null
+
+output=$($RUN_DEMO 2>&1)
+echo "$output"
+if [[ "$output" != *"AWS SDK Exception caught!"* || "$output" != *"Error Code: AccessDeniedException"* ]]; then
+  echo "Test failed: the demo did not report the injected fault"
+  exit 1
+fi
+if [[ "$output" == *"Item inserted."* ]]; then
+  echo "Test failed: the item was inserted despite the fault"
+  exit 1
+fi
+echo "PASS: the demo caught the injected AccessDeniedException"
+
+remove_fault
+echo "Fault removed, running the demo again"
+
+output=$($RUN_DEMO 2>&1)
+echo "$output"
+if [[ "$output" != *"Item retrieved:"* || "$output" != *"Name: Chaos Widget"* ]]; then
+  echo "Test failed: the demo did not read the item back"
+  exit 1
+fi
+name=$(lstk aws dynamodb get-item --table-name Products --key '{"Id": {"S": "123"}}' \
+  --query Item.Name.S --output text)
+if [ "$name" != "Chaos Widget" ]; then
+  echo "Test failed: item 123 in the Products table has name '$name'"
+  exit 1
+fi
+echo "PASS: the item was stored in DynamoDB and read back"
+
+echo "Test passed: the demo handles DynamoDB faults and recovers once they are gone"