Wait for image to be lazy-loaded in tests

Prevents flaky tests

doc/development/testing_guide/flaky_tests.md

@@ -87,6 +87,7 @@ For instance `RETRIES=1 bin/rspec ...` would retry the failing examples once.
   - [Dropdowns rendering upward or downward due to window size and scroll position](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/17660)
   - [Lazy loaded images can cause Capybara to misclick](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/18713)
 - [Triggering JS events before the event handlers are set up](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/18742)
+- [Wait for the image to be lazy-loaded when asserting on a Markdown image's src attribute](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/25408)
 
 #### Capybara viewport size related issues
 

spec/features/snippets/user_creates_snippet_spec.rb

@@ -53,7 +53,7 @@ describe 'User creates snippet', :js do
     page.within('#new_personal_snippet .md-preview-holder') do
       expect(page).to have_content('My Snippet')
 
-      link = find('a.no-attachment-icon img[alt="banana_sample"]')['src']
+      link = find('a.no-attachment-icon img.js-lazy-loaded[alt="banana_sample"]')['src']
       expect(link).to match(%r{/uploads/-/system/user/#{user.id}/\h{32}/banana_sample\.gif\z})
 
       # Adds a cache buster for checking if the image exists as Selenium is now handling the cached regquests
@@ -73,7 +73,7 @@ describe 'User creates snippet', :js do
     click_button('Create snippet')
     wait_for_requests
 
-    link = find('a.no-attachment-icon img[alt="banana_sample"]')['src']
+    link = find('a.no-attachment-icon img.js-lazy-loaded[alt="banana_sample"]')['src']
     expect(link).to match(%r{/uploads/-/system/personal_snippet/#{Snippet.last.id}/\h{32}/banana_sample\.gif\z})
 
     reqs = inspect_requests { visit("#{link}?ran=#{SecureRandom.base64(20)}") }
@@ -98,7 +98,7 @@ describe 'User creates snippet', :js do
       expect(page).to have_selector('strong')
     end
     expect(page).to have_content('Hello World!')
-    link = find('a.no-attachment-icon img[alt="banana_sample"]')['src']
+    link = find('a.no-attachment-icon img.js-lazy-loaded[alt="banana_sample"]')['src']
     expect(link).to match(%r{/uploads/-/system/personal_snippet/#{Snippet.last.id}/\h{32}/banana_sample\.gif\z})
 
     reqs = inspect_requests { visit("#{link}?ran=#{SecureRandom.base64(20)}") }