Add spec for Gitlab::FileFinder

spec/lib/gitlab/file_finder_spec.rb

+require 'spec_helper'
+
+describe Gitlab::FileFinder do
+  let(:project) { create :project }
+  let(:finder) { described_class.new(project, 'master') }
+
+  it 'finds files by name' do
+    result = finder.find('CHANGELOG').first
+
+    expect(result).to match_array(['CHANGELOG', nil])
+  end
+
+  it 'finds files by content' do
+    filename, blob = finder.find('CHANGELOG').last
+
+    expect(filename).to eq('CONTRIBUTING.md')
+    expect(blob.filename).to eq('CONTRIBUTING.md')
+    expect(blob.startline).to be_a(Integer)
+    expect(blob.data).to include('CHANGELOG')
+  end
+end