Add comment in GalleryTemplateTest to explain why we pass query par…

…ameter in tested url

Co-authored-by: George B <[email protected]>

applications/test/GalleryTemplateTest.scala

@@ -43,6 +43,15 @@ import scala.jdk.CollectionConverters._
     )
   }
 
+  //  The Play framework runs integration tests with a TestBrowser that uses a Selenium WebDriver.
+  //  Play 2.9 changes the version of Selenium it depends on under the hood from 3.141.59 to 4.14.1.
+  //  In the previous version of the code the tests above could run one after the other
+  //  without the first affecting the outcome of the second. This is not true anymore,
+  //  it looks like the TestBrowser we use in our test configuration does not automatically clear its cache after each test
+  //  so the second test will always fail. We have similar result if we swap the tests.
+  //  In the following two tests we're adding a flag in the url to make sure
+  //  the cache gets cleared and the tests run independently.
+  //  TODO: Find a way to clear the Selenium WebDriver cache programmatically: https://github.com/guardian/frontend/issues/26837
   it should "select the trail picture for the opengraph image when FacebookShareUseTrailPicFirstSwitch is ON" in {
     FacebookShareUseTrailPicFirstSwitch.switchOn()
     goTo("/lifeandstyle/gallery/2014/nov/24/flying-dogs-in-pictures?page=on") { browser =>