Add spec for emoji and custom emoji filters for ignored tags

spec/lib/banzai/filter/custom_emoji_filter_spec.rb

@@ -18,10 +18,10 @@ RSpec.describe Banzai::Filter::CustomEmojiFilter do
   end
 
   it 'ignores non existent custom emoji' do
-    exp = act = '<p>:foo:</p>'
-    doc = filter(act)
+    exp = '<p>:foo:</p>'
+    doc = filter(exp)
 
-    expect(doc.to_html).to match Regexp.escape(exp)
+    expect(doc.to_html).to eq(exp)
   end
 
   it 'correctly uses the custom emoji URL' do
@@ -77,4 +77,10 @@ RSpec.describe Banzai::Filter::CustomEmojiFilter do
       filter('<p>:tanuki: :party-parrot:</p>')
     end.not_to exceed_all_query_limit(control_count.count)
   end
+
+  context 'ancestor tags' do
+    let(:emoji_name) { ':tanuki:' }
+
+    it_behaves_like 'ignored ancestor tags'
+  end
 end

spec/lib/banzai/filter/emoji_filter_spec.rb

@@ -117,4 +117,10 @@ RSpec.describe Banzai::Filter::EmojiFilter do
 
     expect(doc.to_html).to match(/^This deserves a <gl-emoji.+>, big time\.\z/)
   end
+
+  context 'ancestor tags' do
+    let(:emoji_name) { ':see_no_evil:' }
+
+    it_behaves_like 'ignored ancestor tags'
+  end
 end

spec/support/shared_examples/banzai/filters/ignored_tags_emoji_shared_examples.rb

+# frozen_string_literal: true
+
+RSpec.shared_examples 'ignored ancestor tags' do
+  it 'does not match emoji in a pre tag' do
+    doc = filter("<p><pre>#{emoji_name}</pre></p>")
+
+    expect(doc.css('img').size).to eq 0
+  end
+
+  it 'does not match emoji in code tag' do
+    doc = filter("<p><code>#{emoji_name} wow</code></p>")
+
+    expect(doc.css('img').size).to eq 0
+  end
+
+  it 'does not match emoji in tt tag' do
+    doc = filter("<p><tt>#{emoji_name} yes!</tt></p>")
+
+    expect(doc.css('img').size).to eq 0
+  end
+end