feat(integration-tests): make tracer layer ARNs configurable via env vars

Allow passing custom tracer library versions via environment variables
(NODE_TRACER_LAYER_ARN, PYTHON_TRACER_LAYER_ARN, JAVA_TRACER_LAYER_ARN,
DOTNET_TRACER_LAYER_ARN) while preserving current values as defaults.
This enables testing against custom tracer builds without code changes.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: jchrostek-dd

integration-tests/README.md

@@ -44,6 +44,26 @@ export DATADOG_API_SECRET_ARN="arn:aws:secretsmanager:us-east-1:ACCOUNT_ID:secre
 
 **Docker**: Required for building Lambda functions.
 
+### Configuration
+
+#### Tracer Layer ARNs (Optional)
+
+By default, integration tests use hardcoded Datadog tracer layers. To test with custom tracer versions, set these environment variables:
+
+| Variable | Description | Default |
+|----------|-------------|---------|
+| `NODE_TRACER_LAYER_ARN` | Node.js tracer layer ARN | `arn:aws:lambda:us-east-1:464622532012:layer:Datadog-Node24-x:132` |
+| `PYTHON_TRACER_LAYER_ARN` | Python tracer layer ARN | `arn:aws:lambda:us-east-1:464622532012:layer:Datadog-Python313-ARM:117` |
+| `JAVA_TRACER_LAYER_ARN` | Java tracer layer ARN | `arn:aws:lambda:us-east-1:464622532012:layer:dd-trace-java:25` |
+| `DOTNET_TRACER_LAYER_ARN` | .NET tracer layer ARN | `arn:aws:lambda:us-east-1:464622532012:layer:dd-trace-dotnet-ARM:23` |
+
+**Example:**
+```bash
+# Test with a custom Node.js tracer layer
+export NODE_TRACER_LAYER_ARN="arn:aws:lambda:us-east-1:464622532012:layer:Datadog-Node24-x:135"
+./scripts/local_deploy.sh base
+```
+
 ### Workflow
 
 #### 1. Build and Publish Extension Layer

integration-tests/lib/util.ts

@@ -14,10 +14,11 @@ export const defaultPythonRuntime = lambda.Runtime.PYTHON_3_13;
 export const defaultJavaRuntime = lambda.Runtime.JAVA_21;
 export const defaultDotnetRuntime = lambda.Runtime.DOTNET_8;
 
-export const defaultNodeLayerArn = 'arn:aws:lambda:us-east-1:464622532012:layer:Datadog-Node24-x:132';
-export const defaultPythonLayerArn = 'arn:aws:lambda:us-east-1:464622532012:layer:Datadog-Python313-ARM:117';
-export const defaultJavaLayerArn = 'arn:aws:lambda:us-east-1:464622532012:layer:dd-trace-java:25';
-export const defaultDotnetLayerArn = 'arn:aws:lambda:us-east-1:464622532012:layer:dd-trace-dotnet-ARM:23';
+// Tracer layer ARNs - configurable via env vars, with defaults
+export const defaultNodeLayerArn = process.env.NODE_TRACER_LAYER_ARN || 'arn:aws:lambda:us-east-1:464622532012:layer:Datadog-Node24-x:132';
+export const defaultPythonLayerArn = process.env.PYTHON_TRACER_LAYER_ARN || 'arn:aws:lambda:us-east-1:464622532012:layer:Datadog-Python313-ARM:117';
+export const defaultJavaLayerArn = process.env.JAVA_TRACER_LAYER_ARN || 'arn:aws:lambda:us-east-1:464622532012:layer:dd-trace-java:25';
+export const defaultDotnetLayerArn = process.env.DOTNET_TRACER_LAYER_ARN || 'arn:aws:lambda:us-east-1:464622532012:layer:dd-trace-dotnet-ARM:23';
 
 export const defaultDatadogEnvVariables = {
     DD_API_KEY_SECRET_ARN: datadogSecretArn,