message: docs(developer): integration tests instruction
  ### Description
  Adds documentation on how to run integration tests against Web Components codebase.
  ### Changelog
  **New**
  Documentation on how to run integration tests against Web Components codebase.
diff: - [Contributing to Carbon for IBM.com Web Components package](#contributing-to-carbon-for-ibmcom-web-components-package)
  - [Overview](#overview)
  + - [Get Started](#get-started)
  - [Packages](#packages)
  - [JSDoc](#jsdoc)
  - [Stable Selectors](#stable-selectors)
  - [Environment Variables](#environment-variables)
  - [Storybook](#storybook)
  - [Unit Test Coverage](#unit-test-coverage)
  + - [Running build integration test](#running-build-integration-test)
  + - [Running UI integration test](#running-ui-integration-test)
  - [Further Reading](#further-reading)
  <!-- END doctoc generated TOC please keep comment here to allow auto update -->
  @@ -135,6 +138,8 @@ in the component folder under a sub-folder `__tests__`. The file name structure
  should be `my-component.test.js`. Be sure to include any mock data (if necessary)
  in a `data` subfolder under `__tests__`.
  +All commands below should be run at `packages/web-components` directory.
  +
  To view a coverage report (and run the test suite), you can run:
  ```bash
  @@ -187,6 +192,52 @@ Above options can be used together. This is useful to debug your code as you tes
  > gulp test:unit -s src/components/link-with-icon/__tests__/link-with-icon.test.ts -b Chrome -d -k
  ```
  +## Running build integration test
  +
  +All commands below should be run at `packages/web-components` directory.
  +
  +To run build integration tests:
  +
  +```
  +> yarn test:integration:build
  +```
  +
  +To run a specific set of UI test steps (e.g. running `tests/integration/build/masthead_steps.js` only):
  +
  +```
  +> yarn test:integration:build masthead_steps
  +```
  +
  +By default Chrome runs in headless mode. To enable Chrome UI while running tests:
  +
  +```
  +> CI=false yarn test:integration:build
  +```
  +
  +## Running UI integration test
  +
  +All commands below should be run at `packages/web-components` directory.
  +
  +To run UI integration tests:
  +
  +```
  +> yarn test:integration:ui
  +```
  +
  +UI integration test runs against the Storybook environment. Running UI integration test will be faster by starting Storybook environment beforehand.
  +
  +To run a specific set of UI test steps (e.g. running `src/components/lightbox-media-viewer/__tests__/lightbox-media-viewer_steps.js` only):
  +
  +```
  +> yarn test:integration:ui lightbox-media-viewer_steps
  +```
  +
  +By default Chrome runs in headless mode. To enable Chrome UI while running tests:
  +
  +```
  +> CI=false yarn test:integration:ui
  +```
  +
  ## Further Reading
  - [Coding Conventions](https://github.com/carbon-design-system/carbon-for-ibm-dotcom/blob/master/packages/web-components/docs/coding-conventions.md)
  