Merge branch 'expand-diff-to-full-file' into 'master'

Expand diff to entire file

Closes #19054

See merge request gitlab-org/gitlab-ce!24406

9 files changed, 643 insertions, 82 deletions

diff --git a/spec/controllers/projects/blob_controller_spec.rb b/spec/controllers/projects/blob_controller_spec.rb
index 38957e96798..3801fca09dc 100644
--- a/spec/controllers/projects/blob_controller_spec.rb
+++ b/spec/controllers/projects/blob_controller_spec.rb
@@ -144,54 +144,34 @@ describe Projects::BlobController do
       end
 
       context 'when rendering for merge request' do
-        it 'renders diff context lines Gitlab::Diff::Line array' do
-          do_get(since: 1, to: 5, offset: 10, from_merge_request: true)
-
-          lines = JSON.parse(response.body)
-
-          expect(lines.first).to have_key('type')
-          expect(lines.first).to have_key('rich_text')
-          expect(lines.first).to have_key('rich_text')
+        let(:presenter) { double(:presenter, diff_lines: diff_lines) }
+        let(:diff_lines) do
+          Array.new(3, Gitlab::Diff::Line.new('plain', nil, nil, nil, nil, rich_text: 'rich'))
         end
 
-        context 'when rendering match lines' do
-          it 'adds top match line when "since" is less than 1' do
-            do_get(since: 5, to: 10, offset: 10, from_merge_request: true)
-
-            match_line = JSON.parse(response.body).first
-
-            expect(match_line['type']).to eq('match')
-            expect(match_line['meta_data']).to have_key('old_pos')
-            expect(match_line['meta_data']).to have_key('new_pos')
-          end
-
-          it 'does not add top match line when "since" is equal 1' do
-            do_get(since: 1, to: 10, offset: 10, from_merge_request: true)
-
-            match_line = JSON.parse(response.body).first
-
-            expect(match_line['type']).to be_nil
-          end
+        before do
+          allow(Blobs::UnfoldPresenter).to receive(:new).and_return(presenter)
+        end
 
-          it 'adds bottom match line when "t"o is less than blob size' do
-            do_get(since: 1, to: 5, offset: 10, from_merge_request: true, bottom: true)
+        it 'renders diff context lines Gitlab::Diff::Line array' do
+          do_get(since: 1, to: 2, offset: 0, from_merge_request: true)
 
-            match_line = JSON.parse(response.body).last
+          lines = JSON.parse(response.body)
 
-            expect(match_line['type']).to eq('match')
-            expect(match_line['meta_data']).to have_key('old_pos')
-            expect(match_line['meta_data']).to have_key('new_pos')
+          expect(lines.size).to eq(diff_lines.size)
+          lines.each do |line|
+            expect(line).to have_key('type')
+            expect(line['text']).to eq('plain')
+            expect(line['rich_text']).to eq('rich')
           end
+        end
 
-          it 'does not add bottom match line when "to" is less than blob size' do
-            commit_id = project.repository.commit('master').id
-            blob = project.repository.blob_at(commit_id, 'CHANGELOG')
-            do_get(since: 1, to: blob.lines.count, offset: 10, from_merge_request: true, bottom: true)
+        it 'handles full being true' do
+          do_get(full: true, from_merge_request: true)
 
-            match_line = JSON.parse(response.body).last
+          lines = JSON.parse(response.body)
 
-            expect(match_line['type']).to be_nil
-          end
+          expect(lines.size).to eq(diff_lines.size)
         end
       end
     end
diff --git a/spec/features/merge_request/maintainer_edits_fork_spec.rb b/spec/features/merge_request/maintainer_edits_fork_spec.rb
index aead98dae23..b35f985126c 100644
--- a/spec/features/merge_request/maintainer_edits_fork_spec.rb
+++ b/spec/features/merge_request/maintainer_edits_fork_spec.rb
@@ -26,7 +26,7 @@ describe 'a maintainer edits files on a source-branch of an MR from a fork', :js
     visit project_merge_request_path(target_project, merge_request)
     click_link 'Changes'
     wait_for_requests
-    first('.js-file-title').click_link 'Edit'
+    first('.js-file-title').find('.js-edit-blob').click
     wait_for_requests
   end
 
diff --git a/spec/javascripts/diffs/components/diff_file_header_spec.js b/spec/javascripts/diffs/components/diff_file_header_spec.js
index 1201f066d2f..66c5b17b825 100644
--- a/spec/javascripts/diffs/components/diff_file_header_spec.js
+++ b/spec/javascripts/diffs/components/diff_file_header_spec.js
@@ -23,6 +23,9 @@ describe('diff_file_header', () => {
   });
 
   beforeEach(() => {
+    gon.features = {
+      expandDiffFullFile: true,
+    };
     const diffFile = diffDiscussionMock.diff_file;
 
     diffFile.added_lines = 2;
@@ -382,7 +385,7 @@ describe('diff_file_header', () => {
         props.diffFile.edit_path = '/';
         vm = mountComponentWithStore(Component, { props, store });
 
-        expect(vm.$el.querySelector('.js-edit-blob')).toContainText('Edit');
+        expect(vm.$el.querySelector('.js-edit-blob')).not.toBe(null);
       });
 
       it('should not show edit button when file is deleted', () => {
@@ -576,4 +579,66 @@ describe('diff_file_header', () => {
       });
     });
   });
+
+  describe('expand full file button', () => {
+    beforeEach(() => {
+      props.addMergeRequestButtons = true;
+      props.diffFile.edit_path = '/';
+    });
+
+    it('does not render button', () => {
+      vm = mountComponentWithStore(Component, { props, store });
+
+      expect(vm.$el.querySelector('.js-expand-file')).toBe(null);
+    });
+
+    it('renders button', () => {
+      props.diffFile.is_fully_expanded = false;
+
+      vm = mountComponentWithStore(Component, { props, store });
+
+      expect(vm.$el.querySelector('.js-expand-file')).not.toBe(null);
+    });
+
+    it('shows fully expanded text', () => {
+      props.diffFile.is_fully_expanded = false;
+      props.diffFile.isShowingFullFile = true;
+
+      vm = mountComponentWithStore(Component, { props, store });
+
+      expect(vm.$el.querySelector('.js-expand-file').textContent).toContain('Show changes only');
+    });
+
+    it('shows expand text', () => {
+      props.diffFile.is_fully_expanded = false;
+
+      vm = mountComponentWithStore(Component, { props, store });
+
+      expect(vm.$el.querySelector('.js-expand-file').textContent).toContain('Show full file');
+    });
+
+    it('renders loading icon', () => {
+      props.diffFile.is_fully_expanded = false;
+      props.diffFile.isLoadingFullFile = true;
+
+      vm = mountComponentWithStore(Component, { props, store });
+
+      expect(vm.$el.querySelector('.js-expand-file .loading-container')).not.toBe(null);
+    });
+
+    it('calls toggleFullDiff on click', () => {
+      props.diffFile.is_fully_expanded = false;
+
+      vm = mountComponentWithStore(Component, { props, store });
+
+      spyOn(vm.$store, 'dispatch').and.stub();
+
+      vm.$el.querySelector('.js-expand-file').click();
+
+      expect(vm.$store.dispatch).toHaveBeenCalledWith(
+        'diffs/toggleFullDiff',
+        props.diffFile.file_path,
+      );
+    });
+  });
 });
diff --git a/spec/javascripts/diffs/mock_data/diff_discussions.js b/spec/javascripts/diffs/mock_data/diff_discussions.js
index 4a091b4580b..fd5dd611383 100644
--- a/spec/javascripts/diffs/mock_data/diff_discussions.js
+++ b/spec/javascripts/diffs/mock_data/diff_discussions.js
@@ -288,6 +288,7 @@ export default {
     external_storage: null,
     old_path_html: 'CHANGELOG_OLD',
     new_path_html: 'CHANGELOG',
+    is_fully_expanded: true,
     context_lines_path:
       '/gitlab-org/gitlab-test/blob/c48ee0d1bf3b30453f5b32250ce03134beaa6d13/CHANGELOG/diff',
     highlighted_diff_lines: [
diff --git a/spec/javascripts/diffs/store/actions_spec.js b/spec/javascripts/diffs/store/actions_spec.js
index e47c7906fcb..070bfb2ccd0 100644
--- a/spec/javascripts/diffs/store/actions_spec.js
+++ b/spec/javascripts/diffs/store/actions_spec.js
@@ -30,6 +30,11 @@ import actions, {
   setRenderTreeList,
   setShowWhitespace,
   setRenderIt,
+  requestFullDiff,
+  receiveFullDiffSucess,
+  receiveFullDiffError,
+  fetchFullDiff,
+  toggleFullDiff,
 } from '~/diffs/store/actions';
 import eventHub from '~/notes/event_hub';
 import * as types from '~/diffs/store/mutation_types';
@@ -847,4 +852,129 @@ describe('DiffsStoreActions', () => {
       testAction(setRenderIt, 'file', {}, [{ type: types.RENDER_FILE, payload: 'file' }], [], done);
     });
   });
+
+  describe('requestFullDiff', () => {
+    it('commits REQUEST_FULL_DIFF', done => {
+      testAction(
+        requestFullDiff,
+        'file',
+        {},
+        [{ type: types.REQUEST_FULL_DIFF, payload: 'file' }],
+        [],
+        done,
+      );
+    });
+  });
+
+  describe('receiveFullDiffSucess', () => {
+    it('commits REQUEST_FULL_DIFF', done => {
+      testAction(
+        receiveFullDiffSucess,
+        { filePath: 'test', data: 'test' },
+        {},
+        [{ type: types.RECEIVE_FULL_DIFF_SUCCESS, payload: { filePath: 'test', data: 'test' } }],
+        [],
+        done,
+      );
+    });
+  });
+
+  describe('receiveFullDiffError', () => {
+    it('commits REQUEST_FULL_DIFF', done => {
+      testAction(
+        receiveFullDiffError,
+        'file',
+        {},
+        [{ type: types.RECEIVE_FULL_DIFF_ERROR, payload: 'file' }],
+        [],
+        done,
+      );
+    });
+  });
+
+  describe('fetchFullDiff', () => {
+    let mock;
+    let scrollToElementSpy;
+
+    beforeEach(() => {
+      scrollToElementSpy = spyOnDependency(actions, 'scrollToElement').and.stub();
+
+      mock = new MockAdapter(axios);
+    });
+
+    afterEach(() => {
+      mock.restore();
+    });
+
+    describe('success', () => {
+      beforeEach(() => {
+        mock.onGet(`${gl.TEST_HOST}/context`).replyOnce(200, ['test']);
+      });
+
+      it('dispatches receiveFullDiffSucess', done => {
+        testAction(
+          fetchFullDiff,
+          { context_lines_path: `${gl.TEST_HOST}/context`, file_path: 'test', file_hash: 'test' },
+          null,
+          [],
+          [{ type: 'receiveFullDiffSucess', payload: { filePath: 'test', data: ['test'] } }],
+          done,
+        );
+      });
+
+      it('scrolls to element', done => {
+        fetchFullDiff(
+          { dispatch() {} },
+          { context_lines_path: `${gl.TEST_HOST}/context`, file_path: 'test', file_hash: 'test' },
+        )
+          .then(() => {
+            expect(scrollToElementSpy).toHaveBeenCalledWith('#test');
+
+            done();
+          })
+          .catch(done.fail);
+      });
+    });
+
+    describe('error', () => {
+      beforeEach(() => {
+        mock.onGet(`${gl.TEST_HOST}/context`).replyOnce(500);
+      });
+
+      it('dispatches receiveFullDiffError', done => {
+        testAction(
+          fetchFullDiff,
+          { context_lines_path: `${gl.TEST_HOST}/context`, file_path: 'test', file_hash: 'test' },
+          null,
+          [],
+          [{ type: 'receiveFullDiffError', payload: 'test' }],
+          done,
+        );
+      });
+    });
+  });
+
+  describe('toggleFullDiff', () => {
+    let state;
+
+    beforeEach(() => {
+      state = {
+        diffFiles: [{ file_path: 'test', isShowingFullFile: false }],
+      };
+    });
+
+    it('dispatches fetchFullDiff when file is not expanded', done => {
+      testAction(
+        toggleFullDiff,
+        'test',
+        state,
+        [],
+        [
+          { type: 'requestFullDiff', payload: 'test' },
+          { type: 'fetchFullDiff', payload: state.diffFiles[0] },
+        ],
+        done,
+      );
+    });
+  });
 });
diff --git a/spec/javascripts/diffs/store/mutations_spec.js b/spec/javascripts/diffs/store/mutations_spec.js
index 09ee691b602..270e7d75666 100644
--- a/spec/javascripts/diffs/store/mutations_spec.js
+++ b/spec/javascripts/diffs/store/mutations_spec.js
@@ -680,4 +680,66 @@ describe('DiffsStoreMutations', () => {
       expect(state.showWhitespace).toBe(false);
     });
   });
+
+  describe('REQUEST_FULL_DIFF', () => {
+    it('sets isLoadingFullFile to true', () => {
+      const state = {
+        diffFiles: [{ file_path: 'test', isLoadingFullFile: false }],
+      };
+
+      mutations[types.REQUEST_FULL_DIFF](state, 'test');
+
+      expect(state.diffFiles[0].isLoadingFullFile).toBe(true);
+    });
+  });
+
+  describe('RECEIVE_FULL_DIFF_ERROR', () => {
+    it('sets isLoadingFullFile to false', () => {
+      const state = {
+        diffFiles: [{ file_path: 'test', isLoadingFullFile: true }],
+      };
+
+      mutations[types.RECEIVE_FULL_DIFF_ERROR](state, 'test');
+
+      expect(state.diffFiles[0].isLoadingFullFile).toBe(false);
+    });
+  });
+
+  describe('RECEIVE_FULL_DIFF_SUCCESS', () => {
+    it('sets isLoadingFullFile to false', () => {
+      const state = {
+        diffFiles: [
+          {
+            file_path: 'test',
+            isLoadingFullFile: true,
+            isShowingFullFile: false,
+            highlighted_diff_lines: [],
+            parallel_diff_lines: [],
+          },
+        ],
+      };
+
+      mutations[types.RECEIVE_FULL_DIFF_SUCCESS](state, { filePath: 'test', data: [] });
+
+      expect(state.diffFiles[0].isLoadingFullFile).toBe(false);
+    });
+
+    it('sets isShowingFullFile to true', () => {
+      const state = {
+        diffFiles: [
+          {
+            file_path: 'test',
+            isLoadingFullFile: true,
+            isShowingFullFile: false,
+            highlighted_diff_lines: [],
+            parallel_diff_lines: [],
+          },
+        ],
+      };
+
+      mutations[types.RECEIVE_FULL_DIFF_SUCCESS](state, { filePath: 'test', data: [] });
+
+      expect(state.diffFiles[0].isShowingFullFile).toBe(true);
+    });
+  });
 });
diff --git a/spec/javascripts/diffs/store/utils_spec.js b/spec/javascripts/diffs/store/utils_spec.js
index 599ea9cd420..1f877910125 100644
--- a/spec/javascripts/diffs/store/utils_spec.js
+++ b/spec/javascripts/diffs/store/utils_spec.js
@@ -781,4 +781,49 @@ describe('DiffsStoreUtils', () => {
       ]);
     });
   });
+
+  describe('convertExpandLines', () => {
+    it('converts expanded lines to normal lines', () => {
+      const diffLines = [
+        {
+          type: 'match',
+          old_line: 1,
+          new_line: 1,
+        },
+        {
+          type: '',
+          old_line: 2,
+          new_line: 2,
+        },
+      ];
+
+      const lines = utils.convertExpandLines({
+        diffLines,
+        data: [{ text: 'expanded' }],
+        typeKey: 'type',
+        oldLineKey: 'old_line',
+        newLineKey: 'new_line',
+        mapLine: ({ line, oldLine, newLine }) => ({
+          ...line,
+          old_line: oldLine,
+          new_line: newLine,
+        }),
+      });
+
+      expect(lines).toEqual([
+        {
+          text: 'expanded',
+          new_line: 1,
+          old_line: 1,
+          discussions: [],
+          hasForm: false,
+        },
+        {
+          type: '',
+          old_line: 2,
+          new_line: 2,
+        },
+      ]);
+    });
+  });
 });
diff --git a/spec/lib/gitlab/diff/file_spec.rb b/spec/lib/gitlab/diff/file_spec.rb
index 862590268ca..611c3e946ed 100644
--- a/spec/lib/gitlab/diff/file_spec.rb
+++ b/spec/lib/gitlab/diff/file_spec.rb
@@ -8,6 +8,47 @@ describe Gitlab::Diff::File do
   let(:diff) { commit.raw_diffs.first }
   let(:diff_file) { described_class.new(diff, diff_refs: commit.diff_refs, repository: project.repository) }
 
+  def create_file(file_name, content)
+    Files::CreateService.new(
+      project,
+      project.owner,
+      commit_message: 'Update',
+      start_branch: branch_name,
+      branch_name: branch_name,
+      file_path: file_name,
+      file_content: content
+    ).execute
+
+    project.commit(branch_name).diffs.diff_files.first
+  end
+
+  def update_file(file_name, content)
+    Files::UpdateService.new(
+      project,
+      project.owner,
+      commit_message: 'Update',
+      start_branch: branch_name,
+      branch_name: branch_name,
+      file_path: file_name,
+      file_content: content
+    ).execute
+
+    project.commit(branch_name).diffs.diff_files.first
+  end
+
+  def delete_file(file_name)
+    Files::DeleteService.new(
+      project,
+      project.owner,
+      commit_message: 'Update',
+      start_branch: branch_name,
+      branch_name: branch_name,
+      file_path: file_name
+    ).execute
+
+    project.commit(branch_name).diffs.diff_files.first
+  end
+
   describe '#diff_lines' do
     let(:diff_lines) { diff_file.diff_lines }
 
@@ -675,47 +716,6 @@ describe Gitlab::Diff::File do
     end
     let(:branch_name) { 'master' }
 
-    def create_file(file_name, content)
-      Files::CreateService.new(
-        project,
-        project.owner,
-        commit_message: 'Update',
-        start_branch: branch_name,
-        branch_name: branch_name,
-        file_path: file_name,
-        file_content: content
-      ).execute
-
-      project.commit(branch_name).diffs.diff_files.first
-    end
-
-    def update_file(file_name, content)
-      Files::UpdateService.new(
-        project,
-        project.owner,
-        commit_message: 'Update',
-        start_branch: branch_name,
-        branch_name: branch_name,
-        file_path: file_name,
-        file_content: content
-      ).execute
-
-      project.commit(branch_name).diffs.diff_files.first
-    end
-
-    def delete_file(file_name)
-      Files::DeleteService.new(
-        project,
-        project.owner,
-        commit_message: 'Update',
-        start_branch: branch_name,
-        branch_name: branch_name,
-        file_path: file_name
-      ).execute
-
-      project.commit(branch_name).diffs.diff_files.first
-    end
-
     context 'when empty file is created' do
       it 'returns true' do
         diff_file = create_file('empty.md', '')
@@ -751,4 +751,123 @@ describe Gitlab::Diff::File do
       end
     end
   end
+
+  describe '#fully_expanded?' do
+    let(:project) do
+      create(:project, :custom_repo, files: {})
+    end
+    let(:branch_name) { 'master' }
+
+    context 'when empty file is created' do
+      it 'returns true' do
+        diff_file = create_file('empty.md', '')
+
+        expect(diff_file.fully_expanded?).to be_truthy
+      end
+    end
+
+    context 'when empty file is deleted' do
+      it 'returns true' do
+        create_file('empty.md', '')
+        diff_file = delete_file('empty.md')
+
+        expect(diff_file.fully_expanded?).to be_truthy
+      end
+    end
+
+    context 'when short file with last line removed' do
+      it 'returns true' do
+        create_file('with-content.md', (1..3).to_a.join("\n"))
+        diff_file = update_file('with-content.md', (1..2).to_a.join("\n"))
+
+        expect(diff_file.fully_expanded?).to be_truthy
+      end
+    end
+
+    context 'when a single line is added to empty file' do
+      it 'returns true' do
+        create_file('empty.md', '')
+        diff_file = update_file('empty.md', 'new content')
+
+        expect(diff_file.fully_expanded?).to be_truthy
+      end
+    end
+
+    context 'when single line file is changed' do
+      it 'returns true' do
+        create_file('file.md', 'foo')
+        diff_file = update_file('file.md', 'bar')
+
+        expect(diff_file.fully_expanded?).to be_truthy
+      end
+    end
+
+    context 'when long file is changed' do
+      before do
+        create_file('file.md', (1..999).to_a.join("\n"))
+      end
+
+      context 'when first line is removed' do
+        it 'returns true' do
+          diff_file = update_file('file.md', (2..999).to_a.join("\n"))
+
+          expect(diff_file.fully_expanded?).to be_falsey
+        end
+      end
+
+      context 'when last line is removed' do
+        it 'returns true' do
+          diff_file = update_file('file.md', (1..998).to_a.join("\n"))
+
+          expect(diff_file.fully_expanded?).to be_falsey
+        end
+      end
+
+      context 'when first and last lines are removed' do
+        it 'returns false' do
+          diff_file = update_file('file.md', (2..998).to_a.join("\n"))
+
+          expect(diff_file.fully_expanded?).to be_falsey
+        end
+      end
+
+      context 'when first and last lines are changed' do
+        it 'returns false' do
+          content = (2..998).to_a
+          content.prepend('a')
+          content.append('z')
+          content = content.join("\n")
+
+          diff_file = update_file('file.md', content)
+
+          expect(diff_file.fully_expanded?).to be_falsey
+        end
+      end
+
+      context 'when every line are changed' do
+        it 'returns true' do
+          diff_file = update_file('file.md', "hi\n" * 999)
+
+          expect(diff_file.fully_expanded?).to be_truthy
+        end
+      end
+
+      context 'when all contents are cleared' do
+        it 'returns true' do
+          diff_file = update_file('file.md', "")
+
+          expect(diff_file.fully_expanded?).to be_truthy
+        end
+      end
+
+      context 'when file is binary' do
+        it 'returns true' do
+          diff_file = update_file('file.md', (1..998).to_a.join("\n"))
+          allow(diff_file).to receive(:binary?).and_return(true)
+
+          expect(diff_file.fully_expanded?).to be_truthy
+        end
+      end
+    end
+  end
 end
diff --git a/spec/presenters/blobs/unfold_presenter_spec.rb b/spec/presenters/blobs/unfold_presenter_spec.rb
new file mode 100644
index 00000000000..7ece5f623ce
--- /dev/null
+++ b/spec/presenters/blobs/unfold_presenter_spec.rb
@@ -0,0 +1,159 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Blobs::UnfoldPresenter do
+  include FakeBlobHelpers
+
+  let(:project) { create(:project, :repository) }
+  let(:blob) { fake_blob(path: 'foo', data: "1\n2\n3") }
+  let(:subject) { described_class.new(blob, params) }
+
+  describe '#initialize' do
+    context 'when full is false' do
+      let(:params) { { full: false, since: 2, to: 3, bottom: false, offset: 1, indent: 1 } }
+
+      it 'sets attributes' do
+        result = subject
+
+        expect(result.full?).to eq(false)
+        expect(result.since).to eq(2)
+        expect(result.to).to eq(3)
+        expect(result.bottom).to eq(false)
+        expect(result.offset).to eq(1)
+        expect(result.indent).to eq(1)
+      end
+    end
+
+    context 'when full is true' do
+      let(:params) { { full: true, since: 2, to: 3, bottom: false, offset: 1, indent: 1 } }
+
+      it 'sets other attributes' do
+        result = subject
+
+        expect(result.full?).to eq(true)
+        expect(result.since).to eq(1)
+        expect(result.to).to eq(blob.lines.size)
+        expect(result.bottom).to eq(false)
+        expect(result.offset).to eq(0)
+        expect(result.indent).to eq(0)
+      end
+    end
+  end
+
+  describe '#diff_lines' do
+    let(:total_lines) { 50 }
+    let(:blob) { fake_blob(path: 'foo', data: (1..total_lines).to_a.join("\n")) }
+
+    context 'when "full" is true' do
+      let(:params) { { full: true } }
+
+      it 'returns all lines' do
+        lines = subject.diff_lines
+
+        expect(lines.size).to eq(total_lines)
+
+        lines.each.with_index do |line, index|
+          expect(line.text).to include("LC#{index + 1}")
+          expect(line.text).to eq(line.rich_text)
+          expect(line.type).to be_nil
+        end
+      end
+
+      context 'when last line is empty' do
+        let(:blob) { fake_blob(path: 'foo', data: "1\n2\n") }
+
+        it 'disregards last line' do
+          lines = subject.diff_lines
+
+          expect(lines.size).to eq(2)
+        end
+      end
+    end
+
+    context 'when "since" is equal to 1' do
+      let(:params) { { since: 1, to: 10, offset: 10 } }
+
+      it 'does not add top match line' do
+        line = subject.diff_lines.first
+
+        expect(line.type).to be_nil
+      end
+    end
+
+    context 'when since is greater than 1' do
+      let(:params) { { since: 5, to: 10, offset: 10 } }
+
+      it 'adds top match line' do
+        line = subject.diff_lines.first
+
+        expect(line.type).to eq('match')
+        expect(line.old_pos).to eq(5)
+        expect(line.new_pos).to eq(5)
+      end
+    end
+
+    context 'when "to" is less than blob size' do
+      let(:params) { { since: 1, to: 5, offset: 10, bottom: true } }
+
+      it 'adds bottom match line' do
+        line = subject.diff_lines.last
+
+        expect(line.type).to eq('match')
+        expect(line.old_pos).to eq(-5)
+        expect(line.new_pos).to eq(5)
+      end
+    end
+
+    context 'when "to" is equal to blob size' do
+      let(:params) { { since: 1, to: total_lines, offset: 10, bottom: true } }
+
+      it 'does not add bottom match line' do
+        line = subject.diff_lines.last
+
+        expect(line.type).to be_nil
+      end
+    end
+  end
+
+  describe '#lines' do
+    context 'when scope is specified' do
+      let(:params) { { since: 2, to: 3 } }
+
+      it 'returns lines cropped by params' do
+        expect(subject.lines.size).to eq(2)
+        expect(subject.lines[0]).to include('LC2')
+        expect(subject.lines[1]).to include('LC3')
+      end
+    end
+
+    context 'when full is true' do
+      let(:params) { { full: true } }
+
+      it 'returns all lines' do
+        expect(subject.lines.size).to eq(3)
+        expect(subject.lines[0]).to include('LC1')
+        expect(subject.lines[1]).to include('LC2')
+        expect(subject.lines[2]).to include('LC3')
+      end
+    end
+  end
+
+  describe '#match_line_text' do
+    context 'when bottom is true' do
+      let(:params) { { since: 2, to: 3, bottom: true } }
+
+      it 'returns empty string' do
+        expect(subject.match_line_text).to eq('')
+      end
+    end
+
+    context 'when bottom is false' do
+      let(:params) { { since: 2, to: 3, bottom: false } }
+
+      it 'returns match line string' do
+        expect(subject.match_line_text).to eq("@@ -2,1+2,1 @@")
+      end
+    end
+  end
+end