Best practice: individual or combined tests?

acreadinglist · January 13, 2010, 10:24pm

Hi folks,

I’m pretty new to TDD. Is there a standard approach on this: Is it
better to write individual tests, or combine them? A specific example

if a model Foo validates the presence of both bar and baz, is it
better to have a test each for bar and for baz, or to combine the
validations into a combined bar/baz test?

Thanks!

acreadinglist · January 13, 2010, 11:51pm

acreadinglist wrote:

Hi folks,

I’m pretty new to TDD. Is there a standard approach on this: Is it
better to write individual tests, or combine them? A specific example

if a model Foo validates the presence of both bar and baz, is it
better to have a test each for bar and for baz, or to combine the
validations into a combined bar/baz test?

I’d test them individually. In general, you want each test pretty
atomic.

So for example, take a look at

github.com

marnen/quorum2/blob/master/spec/models/event_spec.rb

# coding: UTF-8

require 'spec_helper'

describe Event do
  describe "(general properties)" do
    it "should act_as_addressed" do
      Event.included_modules.should include(Acts::Addressed::InstanceMethods)
    end

    it "should belong to a State" do
      r = Event.reflect_on_association(:state_raw)
      r.macro.should == :belongs_to
      r.options[:class_name].should == 'Acts::Addressed::State'
      r.options[:foreign_key].should == 'state_id'
    end

    it "should belong to a Country" do
      pending ":include doesn't seem to be a good idea at all -- must investigate" do
        opts = Event.reflect_on_association(:state).options

This file has been truncated. show original

(the validation specs start at line 217). I’ve got separate specs for
each validation.

That code could use some DRYing up, though, and I do sometimes do things
like

['one', 'two', 'three'].each do |field|
  it "should require #{field}" do
    @model.send "#{field}=", nil
    @model.should_not be_valid
  end
end

but note that this still produces three separate specs. I’d feel wrong
if it didn’t.

Thanks!

Best,

Marnen Laibow-Koser
http://www.marnen.org
[email protected]

acreadinglist · January 13, 2010, 11:53pm

Marnen Laibow-Koser wrote:

acreadinglist wrote:

Hi folks,

I’m pretty new to TDD. Is there a standard approach on this: Is it
better to write individual tests, or combine them? A specific example

if a model Foo validates the presence of both bar and baz, is it
better to have a test each for bar and for baz, or to combine the
validations into a combined bar/baz test?

I’d test them individually. In general, you want each test pretty
atomic.

So for example, take a look at
quorum2/spec/models/event_spec.rb at master · marnen/quorum2 · GitHub
(the validation specs start at line 217).

Trust Github to be smart about this! The direct URL for that line (!)
is

github.com

marnen/quorum2/blob/master/spec/models/event_spec.rb#L217


      
          
          
    comment_names.should == ['Nonblank']
            end
          end
          
          
describe "#find_committed" do
            let(:event) { FactoryGirl.create :event }
            let(:event_with_commitments) { Event.includes(commitments: :user).find(event.id) }
          
          

          
  it "should exist with one argument" do
              event.should respond_to(:find_committed)
              event.method(:find_committed).arity.should == 1
            end
          
          
  it "should get a collection of Users when called with :yes or :no" do
              @attending = FactoryGirl.create(:user).tap do |u|
                u.commitments << FactoryGirl.create(:commitment, user: u, event: event, status: true)
              end
              @not_attending = FactoryGirl.create(:user).tap do |u|
                u.commitments << FactoryGirl.create(:commitment, user: u, event: event, status: false)

.

Best,

Marnen Laibow-Koser
http://www.marnen.org
[email protected]