Add specs for DiffParser service

src/api/app/services/diff_parser/line.rb

@@ -9,5 +9,9 @@ def initialize(content:, state:, index:, original_index:, changed_index:)
       @original_index = original_index
       @changed_index = changed_index
     end
+
+    def ==(other)
+      content == other.content && state == other.state && index == other.index && original_index == other.original_index && changed_index == other.changed_index
+    end
   end
 end

src/api/spec/services/diff_parser_spec.rb

@@ -0,0 +1,50 @@
+require 'rails_helper'
+
+RSpec.describe DiffParser, type: :service do
+  let(:content) { Rails.root.join("spec/support/files/#{file}").expand_path }
+  let(:parser) { described_class.new(content: content) }
+
+  let(:result) { result_array.map { |line| DiffParser::Line.new(content: line[0], state: line[1], index: line[2], original_index: line[3], changed_index: line[4]) } }
+
+  subject { parser.call }
+
+  describe '#call' do
+    context 'empty diff' do
+      let(:content) { '' }
+
+      let(:result_array) { [] }
+
+      it { expect(subject).to eq(result) }
+    end
+
+    context 'simple diff' do
+      let(:file) { 'diff_simple.diff' }
+
+      let(:result_array) do
+        [
+          ["@@ -1,1 +1,1 @@\n", 'range', 1, nil, nil],
+          ["-a\n", 'removed', 2, 1, nil],
+          ["+b\n", 'added', 3, nil, 1]
+        ]
+      end
+
+      it 'parses correctly' do expect(subject).to eq(result) end
+    end
+
+    context 'diff with no newline comments' do
+      let(:file) { 'diff_with_no_newline_comments.diff' }
+
+      let(:result_array) do
+        [
+          ["@@ -1,1 +1,1 @@\n", 'range', 1, nil, nil],
+          ["-a\n", 'removed', 2, 1, nil],
+          ["\\ No newline at end of file\n", 'comment', 3, nil, nil],
+          ["+b\n", 'added', 4, nil, 1],
+          ["\\ No newline at end of file\n", 'comment', 5, nil, nil]
+        ]
+      end
+
+      it 'parses correctly' do expect(subject).to eq(result) end
+    end
+  end
+end

src/api/spec/support/files/diff_simple.diff

@@ -0,0 +1,3 @@
+@@ -1,1 +1,1 @@
+-a
++b

src/api/spec/support/files/diff_with_no_newline_comments.diff

@@ -0,0 +1,5 @@
+@@ -1,1 +1,1 @@
+-a
+\ No newline at end of file
++b
+\ No newline at end of file