1 files changed, 67 insertions, 0 deletions
diff --git a/spec/lib/gitlab/word_diff/parser_spec.rb b/spec/lib/gitlab/word_diff/parser_spec.rb
new file mode 100644
index 00000000000..3aeefb57a02
--- /dev/null
+++ b/spec/lib/gitlab/word_diff/parser_spec.rb
@@ -0,0 +1,67 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::WordDiff::Parser do
+  subject(:parser) { described_class.new }
+
+  describe '#parse' do
+    subject { parser.parse(diff.lines).to_a }
+
+    let(:diff) do
+      <<~EOF
+      @@ -1,14 +1,13 @@
+      ~
+       Unchanged line
+      ~
+      ~
+      -Old change
+      +New addition
+        unchanged content
+      ~
+      @@ -50,14 +50,13 @@
+      +First change
+        same same same_
+      -removed_
+      +added_
+       end of the line
+      ~
+      ~
+      EOF
+    end
+
+    it 'returns a collection of lines' do
+      diff_lines = subject
+
+      aggregate_failures do
+        expect(diff_lines.count).to eq(7)
+
+        expect(diff_lines.map(&:to_hash)).to match_array(
+          [
+            a_hash_including(index: 0, old_pos: 1, new_pos: 1, text: '', type: nil),
+            a_hash_including(index: 1, old_pos: 2, new_pos: 2, text: 'Unchanged line', type: nil),
+            a_hash_including(index: 2, old_pos: 3, new_pos: 3, text: '', type: nil),
+            a_hash_including(index: 3, old_pos: 4, new_pos: 4, text: 'Old changeNew addition unchanged content', type: nil),
+            a_hash_including(index: 4, old_pos: 50, new_pos: 50, text: '@@ -50,14 +50,13 @@', type: 'match'),
+            a_hash_including(index: 5, old_pos: 50, new_pos: 50, text: 'First change same same same_removed_added_end of the line', type: nil),
+            a_hash_including(index: 6, old_pos: 51, new_pos: 51, text: '', type: nil)
+          ]
+        )
+      end
+    end
+
+    it 'restarts object index after several calls to Enumerator' do
+      enumerator = parser.parse(diff.lines)
+
+      2.times do
+        expect(enumerator.first.index).to eq(0)
+      end
+    end
+
+    context 'when diff is empty' do
+      let(:diff) { '' }
+
+      it { is_expected.to eq([]) }
+    end
+  end
+end