added tests

spec/uploaders/file_uploader_spec.rb

@@ -0,0 +1,18 @@
+require 'rails_helper'
+
+describe FileUploader do
+  let(:file_path) { Rails.root.join('db', 'seeds', 'fibonacci', 'exercise.rb') }
+  let(:uploader) { described_class.new(FactoryGirl.create(:file)) }
+
+  before(:each) { uploader.store!(File.open(file_path, 'r')) }
+  after(:each) { uploader.remove! }
+
+  it 'uses the specified storage directory' do
+    expect(uploader.file.path).to start_with(Rails.root.join('public', uploader.store_dir).to_s)
+    expect(uploader.file.path).to end_with(file_path.basename.to_s)
+  end
+
+  it 'stores the file content' do
+    expect(uploader.file.read).to eq(File.read(file_path))
+  end
+end