[librsvg/rustify-rsvg-convert] (6 commits) ...Merge branch 'refactor-test-utils' into 'rustify-rsvg-convert'

[Federico Mena Quintero <federico src gnome org>]

Summary of changes:

  89563e6... Draft a predicate to compare a PNG file's contents to a ref (*)
  25aad2a... Refactor test_utils and move it to the tests (*)
  bfafd58... Implement PngPredicate.with_contents() using tests::referen (*)
  7aad1b5... Add test to verify that rsvg-convert renders the background (*)
  127a945... Fix typo in test name. (*)
  090e292... Merge branch 'refactor-test-utils' into 'rustify-rsvg-conve

(*) This commit already existed in another branch; no separate mail sent