Allow selenium image configuration

src/Command/BehatCommand.php

@@ -25,25 +25,6 @@ class BehatCommand extends AbstractMoodleCommand
 {
     use ExecuteTrait;
 
-    /**
-     * Selenium legacy Firefox image.
-     */
-    private string $seleniumLegacyFirefoxImage = 'selenium/standalone-firefox:2.53.1';
-
-    /**
-     * Selenium standalone Firefox image.
-     *
-     * @todo: Make this configurable.
-     */
-    private string $seleniumFirefoxImage = 'selenium/standalone-firefox:3';
-
-    /**
-     * Selenium standalone Chrome image.
-     *
-     * @todo: Make this configurable.
-     */
-    private string $seleniumChromeImage = 'selenium/standalone-chrome:3';
-
     /**
      * Wait this many microseconds for Selenium server to start/stop.
      *
@@ -150,13 +131,7 @@ private function startServerProcesses(InputInterface $input): void
             $profile = getenv('MOODLE_BEHAT_DEFAULT_BROWSER') ?: (getenv('MOODLE_APP') ? 'chrome' : 'firefox');
         }
 
-        if ($profile === 'chrome') {
-            $image = $this->seleniumChromeImage;
-        } elseif ($this->usesLegacyPhpWebdriver()) {
-            $image = $this->seleniumLegacyFirefoxImage;
-        } else {
-            $image = $this->seleniumFirefoxImage;
-        }
+        $image = $this->getSeleniumImage($profile);
 
         $cmd = [
             'docker',
@@ -226,4 +201,23 @@ private function usesLegacyPhpWebdriver(): bool
 
         return strpos(file_get_contents($composerlock), 'instaclick/php-webdriver') !== false;
     }
+
+    private function getSeleniumImage(string $profile): string
+    {
+        $image = getenv('MOODLE_BEHAT_SELENIUM_IMAGE');
+
+        if (!empty($image)) {
+            return $image;
+        }
+
+        if ($profile === 'chrome') {
+            return getenv('MOODLE_BEHAT_SELENIUM_CHROME_IMAGE') ?: 'selenium/standalone-chrome:3';
+        }
+
+        if ($this->usesLegacyPhpWebdriver()) {
+            return 'selenium/standalone-firefox:2.53.1';
+        }
+
+        return getenv('MOODLE_BEHAT_SELENIUM_FIREFOX_IMAGE') ?: 'selenium/standalone-firefox:3';
+    }
 }