Document code, update README.

Author: onurtemizkan

packages/integration-tests/README.md

@@ -56,6 +56,9 @@ To filter tests by their title:
 
 You can refer to [Playwright documentation](https://playwright.dev/docs/test-cli) for other CLI options.
 
+You can set env variable `PW_BUNDLE` to set specific `browser` and `tracing` build or bundle to test against.
+Available options: `esm`, `dist`, `bundle`, `bundle_min`, `bundle_es6`, `bundle_es6_min`
+
 ### Troubleshooting
 
 Apart from [Playwright-specific issues](https://playwright.dev/docs/troubleshooting), below are common issues that might occur while writing tests for Sentry Browser SDK.

packages/integration-tests/utils/generatePage.ts

@@ -9,7 +9,11 @@ import webpackConfig from '../webpack.config';
 const PACKAGE_PATH = '../../packages';
 
 const bundleKey = process.env.PW_BUNDLE;
+
+// `esm` and `dist` builds are modules that can be imported / aliased by webpack
 const useCompiledModule = bundleKey && (bundleKey === 'esm' || bundleKey === 'dist');
+
+// bundles need to be injected into HTML before Sentry initialization.
 const useBundle = bundleKey && !useCompiledModule;
 
 const BUNDLE_PATHS: Record<string, Record<string, string>> = {
@@ -26,6 +30,7 @@ const BUNDLE_PATHS: Record<string, Record<string, string>> = {
     esm: 'esm/index.js',
     bundle: 'build/bundle.tracing.js',
     bundle_min: 'build/bundle.tracing.min.js',
+    // `tracing` doesn't have an es6 build
     bundle_es6: 'build/bundle.tracing.js',
     bundle_es6_min: 'build/bundle.tracing.min.js',
   },