Issue #2996476 by andrewbelcher, dawehner, jhedstrom: Allow setting the base...

Issue #2996476 by andrewbelcher, dawehner, jhedstrom: Allow setting the base url for browsertest output

core/phpunit.xml.dist

@@ -21,6 +21,11 @@
     <env name="SIMPLETEST_DB" value=""/>
     <!-- Example BROWSERTEST_OUTPUT_DIRECTORY value: /path/to/webroot/sites/simpletest/browser_output -->
     <env name="BROWSERTEST_OUTPUT_DIRECTORY" value=""/>
+    <!-- To have browsertest output use an alternative base URL. For example if
+     SIMPLETEST_BASE_URL is an internal DDEV URL, you can set this to the
+     external DDev URL so you can follow the links directly.
+    -->
+    <env name="BROWSERTEST_OUTPUT_BASE_URL" value=""/>
     <!-- To disable deprecation testing completely uncomment the next line. -->
     <!-- <env name="SYMFONY_DEPRECATIONS_HELPER" value="disabled"/> -->
     <!-- Example for changing the driver class for mink tests MINK_DRIVER_CLASS value: 'Drupal\FunctionalJavascriptTests\DrupalSelenium2Driver' -->

core/tests/Drupal/Tests/BrowserHtmlDebugTrait.php

@@ -65,6 +65,13 @@ trait BrowserHtmlDebugTrait {
    */
   protected $htmlOutputTestId;
 
+  /**
+   * The Base URI to use for links to the output files.
+   *
+   * @var string
+   */
+  protected $htmlOutputBaseUrl;
+
   /**
    * Formats HTTP headers as string for HTML output logging.
    *
@@ -118,7 +125,7 @@ protected function htmlOutput($message = NULL) {
     file_put_contents($this->htmlOutputCounterStorage, $this->htmlOutputCounter++);
     // Do not use file_create_url() as the module_handler service might not be
     // available.
-    $uri = $GLOBALS['base_url'] . '/sites/simpletest/browser_output/' . $html_output_filename;
+    $uri = $this->htmlOutputBaseUrl . '/sites/simpletest/browser_output/' . $html_output_filename;
     file_put_contents($this->htmlOutputFile, $uri . "\n", FILE_APPEND);
   }
 
@@ -131,6 +138,7 @@ protected function htmlOutput($message = NULL) {
   protected function initBrowserOutputFile() {
     $browser_output_file = getenv('BROWSERTEST_OUTPUT_FILE');
     $this->htmlOutputEnabled = is_file($browser_output_file);
+    $this->htmlOutputBaseUrl = getenv('BROWSERTEST_OUTPUT_BASE_URL') ?: $GLOBALS['base_url'];
     if ($this->htmlOutputEnabled) {
       $this->htmlOutputFile = $browser_output_file;
       $this->htmlOutputClassName = str_replace("\\", "_", get_called_class());