feat(codebuild): adds report group type property (aws#20178)

fixes aws#14279.
Introduces optional property to the ReportGroup to define the type of the report group (either 'TEST' or 'CODE_COVERAGE'). It just passes down the property to the underlying CfnReportGroup.

----

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* [x] Have you followed the guidelines in our [Contributing guide?](https://github.com/aws/aws-cdk/blob/master/CONTRIBUTING.md)

### Adding new Unconventional Dependencies:

* [x] This PR adds new unconventional dependencies following the process described [here](https://github.com/aws/aws-cdk/blob/master/CONTRIBUTING.md/#adding-new-unconventional-dependencies)

### New Features

* [x] Have you added the new feature to an [integration test](https://github.com/aws/aws-cdk/blob/master/INTEGRATION_TESTS.md)?
	* [x] Did you use `yarn integ` to deploy the infrastructure and generate the snapshot (i.e. `yarn integ` without `--dry-run`)?

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/@aws-cdk/aws-codebuild/README.md

@@ -493,7 +493,32 @@ const project = new codebuild.Project(this, 'Project', {
 });
 ```
 
-If you do that, you need to grant the project's role permissions to write reports to that report group:
+For a code coverage report, you can specify a report group with the code coverage report group type.
+
+```ts
+declare const source: codebuild.Source;
+
+// create a new ReportGroup
+const reportGroup = new codebuild.ReportGroup(this, 'ReportGroup', {
+    type: codebuild.ReportGroupType.CODE_COVERAGE
+});
+
+const project = new codebuild.Project(this, 'Project', {
+  source,
+  buildSpec: codebuild.BuildSpec.fromObject({
+    // ...
+    reports: {
+      [reportGroup.reportGroupArn]: {
+        files: '**/*',
+        'base-directory': 'build/coverage-report.xml',
+        'file-format': 'JACOCOXML'
+      },
+    },
+  }),
+});
+```
+
+If you specify a report group, you need to grant the project's role permissions to write reports to that report group:
 
 ```ts
 declare const project: codebuild.Project;

packages/@aws-cdk/aws-codebuild/lib/report-group.ts

@@ -58,6 +58,20 @@ abstract class ReportGroupBase extends cdk.Resource implements IReportGroup {
   }
 }
 
+/**
+ * The type of reports in the report group.
+ */
+export enum ReportGroupType {
+  /**
+   * The report group contains test reports.
+   */
+  TEST = 'TEST',
+  /**
+   * The report group contains code coverage reports.
+   */
+  CODE_COVERAGE = 'CODE_COVERAGE'
+}
+
 /**
  * Construction properties for {@link ReportGroup}.
  */
@@ -93,6 +107,16 @@ export interface ReportGroupProps {
    * @default RemovalPolicy.RETAIN
    */
   readonly removalPolicy?: cdk.RemovalPolicy;
+
+  /**
+   * The type of report group. This can be one of the following values:
+   *
+   * - **TEST** - The report group contains test reports.
+   * - **CODE_COVERAGE** - The report group contains code coverage reports.
+   *
+   * @default TEST
+   */
+  readonly type?: ReportGroupType
 }
 
 /**
@@ -125,7 +149,7 @@ export class ReportGroup extends ReportGroupBase {
     });
 
     const resource = new CfnReportGroup(this, 'Resource', {
-      type: 'TEST',
+      type: props.type ? props.type : ReportGroupType.TEST,
       exportConfig: {
         exportConfigType: props.exportBucket ? 'S3' : 'NO_EXPORT',
         s3Destination: props.exportBucket

packages/@aws-cdk/aws-codebuild/test/report-group.test.ts

@@ -4,6 +4,7 @@ import * as kms from '@aws-cdk/aws-kms';
 import * as s3 from '@aws-cdk/aws-s3';
 import * as cdk from '@aws-cdk/core';
 import * as codebuild from '../lib';
+import { ReportGroupType } from '../lib';
 
 /* eslint-disable quote-props */
 /* eslint-disable quotes */
@@ -142,4 +143,26 @@ describe('Test Reports Groups', () => {
       "UpdateReplacePolicy": "Delete",
     });
   });
+
+  test('can be created with type=CODE_COVERAGE', () => {
+    const stack = new cdk.Stack();
+
+    new codebuild.ReportGroup(stack, 'ReportGroup', {
+      type: ReportGroupType.CODE_COVERAGE,
+    });
+
+    Template.fromStack(stack).hasResourceProperties('AWS::CodeBuild::ReportGroup', {
+      "Type": "CODE_COVERAGE",
+    });
+  });
+
+  test('defaults to report group type=TEST when not specified explicitly', () => {
+    const stack = new cdk.Stack();
+
+    new codebuild.ReportGroup(stack, 'ReportGroup', {});
+
+    Template.fromStack(stack).hasResourceProperties('AWS::CodeBuild::ReportGroup', {
+      "Type": "TEST",
+    });
+  });
 });