5 files changed, 99 insertions, 0 deletions
diff --git a/spec/features/markdown_spec.rb b/spec/features/markdown_spec.rb
index fdd8cf07b12..e836d81c40b 100644
--- a/spec/features/markdown_spec.rb
+++ b/spec/features/markdown_spec.rb
@@ -212,6 +212,7 @@ describe 'GitLab Markdown', feature: true do
         expect(doc).to reference_commit_ranges
         expect(doc).to reference_commits
         expect(doc).to reference_labels
+        expect(doc).to reference_milestones
       end
     end
 
diff --git a/spec/fixtures/markdown.md.erb b/spec/fixtures/markdown.md.erb
index e8dfc5c0eb1..302b750aee5 100644
--- a/spec/fixtures/markdown.md.erb
+++ b/spec/fixtures/markdown.md.erb
@@ -214,6 +214,14 @@ References should be parseable even inside _<%= merge_request.to_reference %>_ e
 - Ignored in links: [Link to <%= simple_label.to_reference %>](#label-link)
 - Link to label by reference: [Label](<%= label.to_reference %>)
 
+#### MilestoneReferenceFilter
+
+- Milestone: <%= milestone.to_reference %>
+- Milestone in another project: <%= xmilestone.to_reference(project) %>
+- Ignored in code: `<%= milestone.to_reference %>`
+- Ignored in links: [Link to <%= milestone.to_reference %>](#milestone-link)
+- Link to milestone by URL: [Milestone](<%= urls.namespace_project_milestone_url(milestone.project.namespace, milestone.project, milestone) %>)
+
 ### Task Lists
 
 - [ ] Incomplete task 1
diff --git a/spec/lib/banzai/filter/milestone_reference_filter_spec.rb b/spec/lib/banzai/filter/milestone_reference_filter_spec.rb
new file mode 100644
index 00000000000..c53e780d354
--- /dev/null
+++ b/spec/lib/banzai/filter/milestone_reference_filter_spec.rb
@@ -0,0 +1,73 @@
+require 'spec_helper'
+
+describe Banzai::Filter::MilestoneReferenceFilter, lib: true do
+  include FilterSpecHelper
+
+  let(:project) { create(:project, :public) }
+  let(:milestone)   { create(:milestone, project: project) }
+
+  it 'requires project context' do
+    expect { described_class.call('') }.to raise_error(ArgumentError, /:project/)
+  end
+
+  %w(pre code a style).each do |elem|
+    it "ignores valid references contained inside '#{elem}' element" do
+      exp = act = "<#{elem}>milestone #{milestone.to_reference}</#{elem}>"
+      expect(reference_filter(act).to_html).to eq exp
+    end
+  end
+
+  context 'internal reference' do
+    let(:reference) { milestone.to_reference }
+
+    it 'links to a valid reference' do
+      doc = reference_filter("See #{reference}")
+
+      expect(doc.css('a').first.attr('href')).to eq urls.
+        namespace_project_milestone_url(project.namespace, project, milestone)
+    end
+
+    it 'links with adjacent text' do
+      doc = reference_filter("milestone (#{reference}.)")
+      expect(doc.to_html).to match(/\(<a.+><i.+><\/i> #{Regexp.escape(milestone.title)}<\/a>\.\)/)
+    end
+
+    it 'includes a title attribute' do
+      doc = reference_filter("milestone #{reference}")
+      expect(doc.css('a').first.attr('title')).to eq "Milestone: #{milestone.title}"
+    end
+
+    it 'escapes the title attribute' do
+      milestone.update_attribute(:title, %{"></a>whatever<a title="})
+
+      doc = reference_filter("milestone #{reference}")
+      expect(doc.text).to eq "milestone  #{milestone.title}"
+    end
+
+    it 'includes default classes' do
+      doc = reference_filter("milestone #{reference}")
+      expect(doc.css('a').first.attr('class')).to eq 'gfm gfm-milestone'
+    end
+
+    it 'includes a data-project attribute' do
+      doc = reference_filter("milestone #{reference}")
+      link = doc.css('a').first
+
+      expect(link).to have_attribute('data-project')
+      expect(link.attr('data-project')).to eq project.id.to_s
+    end
+
+    it 'includes a data-milestone attribute' do
+      doc = reference_filter("See #{reference}")
+      link = doc.css('a').first
+
+      expect(link).to have_attribute('data-milestone')
+      expect(link.attr('data-milestone')).to eq milestone.id.to_s
+    end
+
+    it 'adds to the results hash' do
+      result = reference_pipeline_result("milestone #{reference}")
+      expect(result[:references][:milestone]).to eq [milestone]
+    end
+  end
+end
diff --git a/spec/support/markdown_feature.rb b/spec/support/markdown_feature.rb
index d6d3062a197..5d97fdd4882 100644
--- a/spec/support/markdown_feature.rb
+++ b/spec/support/markdown_feature.rb
@@ -59,6 +59,10 @@ class MarkdownFeature
     @label ||= create(:label, name: 'awaiting feedback', project: project)
   end
 
+  def milestone
+    @milestone ||= create(:milestone, project: project)
+  end
+
   # Cross-references -----------------------------------------------------------
 
   def xproject
@@ -93,6 +97,10 @@ class MarkdownFeature
     end
   end
 
+  def xmilestone
+    @xmilestone ||= create(:milestone, project: xproject)
+  end
+
   def urls
     Gitlab::Application.routes.url_helpers
   end
diff --git a/spec/support/matchers/markdown_matchers.rb b/spec/support/matchers/markdown_matchers.rb
index 7eadcd58c1f..b251e7f8f23 100644
--- a/spec/support/matchers/markdown_matchers.rb
+++ b/spec/support/matchers/markdown_matchers.rb
@@ -130,6 +130,15 @@ module MarkdownMatchers
     end
   end
 
+  # MilestoneReferenceFilter
+  matcher :reference_milestones do
+    set_default_markdown_messages
+
+    match do |actual|
+      expect(actual).to have_selector('a.gfm.gfm-milestone', count: 3)
+    end
+  end
+
   # TaskListFilter
   matcher :parse_task_lists do
     set_default_markdown_messages