fix(apig): Move 'selectionPattern to integrationResponses` (aws#1636)

The property was modeled in the wrong place, rendering it unusable.
Moved it to the correct location instead, and added a validation test.

Fixes aws#1608

packages/@aws-cdk/aws-apigateway/lib/integration.ts

@@ -86,15 +86,6 @@ export interface IntegrationOptions {
    */
   integrationResponses?: IntegrationResponse[];
 
-  /**
-   * The templates that are used to transform the integration response body.
-   * Specify templates as key-value pairs (string-to-string mappings), with a
-   * content type as the key and a template as the value.
-   *
-   * @see http://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-mapping-template-reference.html
-   */
-  selectionPattern?: string;
-
   /**
    * The type of network connection to the integration endpoint.
    * @default ConnectionType.Internet
@@ -243,6 +234,17 @@ export enum ConnectionType {
 }
 
 export interface IntegrationResponse {
+  /**
+   * Specifies the regular expression (regex) pattern used to choose an integration response based on the response from
+   * the back end. For example, if the success response returns nothing and the error response returns some string, you
+   * could use the ``.+`` regex to match error response. However, make sure that the error response does not contain any
+   * newline (``\n``) character in such cases. If the back end is an AWS Lambda function, the AWS Lambda function error
+   * header is matched. For all other HTTP and AWS back ends, the HTTP status code is matched.
+   *
+   * @see https://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-integration-settings-integration-response.html
+   */
+  selectionPattern?: string;
+
   /**
    * The status code that API Gateway uses to map the integration response to
    * a MethodResponse status code.

packages/@aws-cdk/aws-apigateway/test/test.method.ts

@@ -302,5 +302,51 @@ export = {
     // THEN
     test.throws(() => api.root.addMethod('GET', integration), /cannot set 'vpcLink' where 'connectionType' is INTERNET/);
     test.done();
+  },
+
+  'multiple integration responses can be used'(test: Test) { // @see https://github.com/awslabs/aws-cdk/issues/1608
+    // GIVEN
+    const stack = new cdk.Stack();
+    const api = new apigateway.RestApi(stack, 'test-api', { deploy: false });
+
+    // WHEN
+    api.root.addMethod('GET', new apigateway.AwsIntegration({
+      service: 'foo-service',
+      action: 'BarAction',
+      options: {
+        integrationResponses: [
+          {
+            statusCode: '200',
+            responseTemplates: { 'application/json': JSON.stringify({ success: true }) },
+          },
+          {
+            selectionPattern: 'Invalid',
+            statusCode: '503',
+            responseTemplates: { 'application/json': JSON.stringify({ success: false, message: 'Invalid Request' }) },
+          }
+        ],
+      }
+    }));
+
+    // THEN
+    expect(stack).to(haveResource('AWS::ApiGateway::Method', {
+      Integration: {
+        IntegrationHttpMethod: 'POST',
+        IntegrationResponses: [
+          {
+            ResponseTemplates: { 'application/json': '{"success":true}' },
+            StatusCode: '200',
+          },
+          {
+            ResponseTemplates: { 'application/json': '{"success":false,"message":"Invalid Request"}' },
+            SelectionPattern: 'Invalid',
+            StatusCode: '503',
+          }
+        ],
+        Type: 'AWS',
+        Uri: { 'Fn::Join': ['', ['arn:', { Ref: 'AWS::Partition' }, ':apigateway:', { Ref: 'AWS::Region' }, ':foo-service:action/BarAction']]}
+      }
+    }));
+    test.done();
   }
 };