Mini Test testing save on one and many trips

Question

I know there is a balance to be struck between writing dry code and damp code but I have the feeling that this is a bit too repeative. Is there a terse yet self explainatory way to rewrite these tests?

class TripTest < ActiveSupport::TestCase
 def setup
 @trip = trips(:one)
 @invoice = invoices(:one)
 end
 test 'trip can save' do
 trip = Trip.new
 trip.departure_date = "2040-03-24"
 trip.depart_airport = "DHW"
 trip.arrive_airport = "ABC"
 trip.invoice_id = 123534
 assert trip.save, "Error message: #{trip.errors.full_messages}"
 end
 test "one invoice can have multiple trips" do
 trip = Trip.new
 trip.departure_date = "2040-03-24"
 trip.depart_airport = "DHW"
 trip.arrive_airport = "ABC"
 trip.invoice_id = 123534
 @invoice.trips.push(trip)
 @invoice.save
 trip = Trip.new
 trip.departure_date = "2040-03-24"
 trip.depart_airport = "ICN"
 trip.arrive_airport = "XYZ"
 trip.invoice_id = 123534
 @invoice.trips.push(trip)
 @invoice.save
 assert @invoice.trips.size > 1
 end

Answer 1

If you're writing verbose tests, your test suite will skyrocket in length.

There are worse problems to have but your best asset to address this problem is a comprehensive test_helper class.

It doesn't matter what you call the file. Just load it up into your main test file with a require_relative.

In your example, it's fairly obvious which code is being repeated between methods. So you could refactor your code as follows:

# in test_helpers.rb
module TestHelpers
 def initialize_sample_trip(options={})
 Trip.new(
 departure_date: options[:departure_date] || "2040-03-24"
 default_airport: options[:default_airport] || "DHW"
 arrive_airport: options[:arrive_airport] || "ABC"
 invoice_id: options[:invoice_id] || 123534
 )
 end
end

...

# in your main test file
require_relative './test_helpers.rb'
class TripTest < ActiveSupport::TestCase
 include TestHelpers
 def setup
 @trip = trips(:one)
 @invoice = invoices(:one)
 end
 test 'trip can save' do
 trip = initialize_sample_trip
 assert trip.save, "Error message: #{trip.errors.full_messages}"
 end
 test "one invoice can have multiple trips" do
 trip1 = initialize_sample_trip
 @invoice.trips.push(trip1)
 @invoice.save
 trip2 = initialize_sample_trip(
 depart_airport: ICN, arrive_airport: "XYZ"
 )
 @invoice.trips.push(trip)
 @invoice.save
 assert @invoice.trips.size > 1
 end

This can be considered a "factory" design pattern. There are also various gems which can assist with this such as factory_girl or faker.