Media Images should be rendered at a reasonable size by default

I believe we should adjust \Drupal\Tests\media\FunctionalJavascript\MediaDisplayTest::testMediaDisplay() as well, but let's see what the testbot says

Looks good to me, just a minor remark:

+++ b/core/modules/media/tests/src/FunctionalJavascript/MediaDisplayTest.php
@@ -163,8 +161,8 @@ public function testMediaDisplay() {
     // Only one element is present inside the media container.
     $this->assertEquals(1, count($page->findAll('css', '.field--name-field-related-media article.media--type-image > div')));
-    // Assert the image is present, with "medium" image style.
-    $assert_session->elementExists('css', '.field--name-field-related-media article.media--type-image img.image-style-medium');
+    // Assert the image is present.
+    $assert_session->elementExists('css', '.field--name-field-related-media article.media--type-image');
   }

If we are not checking the img tag, then this last assert is redundant to the previous one. Maybe we can assert that .field--name-field-related-media article.media--type-image img exists, without specifying any class?

+++ b/core/modules/media/tests/src/FunctionalJavascript/MediaDisplayTest.php
@@ -81,10 +81,8 @@ public function testMediaDisplay() {
-    $assert_session->elementExists('css', 'img.image-style-medium', $media_item);

We shouldn't remove this line; just change it to $assert_session->elementExists('css', 'img', $media_item);

Also, we could assert the original image (albeit not perfectly), by getting the 'class' attribute, splitting it by whitespace, and asserting that none of the classes start with image-style-.

Makes sense, although it is IMHO a bad idea for an actual site to ever use original image, you never know what your users are uploading, might be huge 5MB pictures. But lets make media and normal image fields consistent and then we can think about adding something like a HD image style that would be used by default to standard?

About the test, we might also be able to assert the actual src attribute of the image?

In paragraphs test, we have something like this, except we'd want to use a getAtribute() on the image element that we load with elementExists():

    $img1_url = file_create_url(\Drupal::token()->replace('public://[date:custom:Y]-[date:custom:m]/myImage1.jpg'));
    $img2_url = file_create_url(\Drupal::token()->replace('public://[date:custom:Y]-[date:custom:m]/myImage2.jpg'));

    // Check the text and image after publish.
    $this->assertText('Test text 1');
    $this->assertRaw('<img src="' . file_url_transform_relative($img1_url));

I think this looks right.

Ah, much better!

I tested this manually and confirmed Media image fields now behave the same way as image fields do by default.

+++ b/core/modules/media/tests/src/FunctionalJavascript/MediaDisplayTest.php
@@ -81,10 +81,13 @@ public function testMediaDisplay() {
+    $expected_image_src = file_url_transform_relative(file_create_url(\Drupal::token()->replace('public://[date:custom:Y]-[date:custom:m]/example_1.jpeg')));

I was surprised by file_url_transform_relative() here, but I couldn't come up with any specific concern. So seems okay.

Committed to 8.5.x. Thanks!