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Temping

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Temping allows you to create arbitrary ActiveRecord models backed by a temporary SQL table for use in tests. You may need to do something like this if you're testing a module that is meant to be mixed into ActiveRecord models without relying on a concrete class.

Temping will use your existing database connection. As we're using temporary tables all data will be dropped when the database connection is terminated.

Table of Contents

Installation

In your Gemfile:

gem "temping"

In test_helper.rb add the following block to ActiveSupport::TestCase:

class ActiveSupport::TestCase
  # ...
  teardown do
    Temping.teardown
  end
  # ...
end

Or, if you're using rspec, in spec_helper.rb add the following block to RSpec.configure:

RSpec.configure do |config|
  # ...
  config.after do
    Temping.teardown
  end
  # ...
end

Alternatively you may want to just cleanup tables but keep defined models in memory:

Temping.cleanup

Examples

The basic setup of a model involves calling create with a symbol that represents the class name of the model you wish to create. By default, this will create a temporary table with an id column.

Temping.create(:dog)

Dog.create # => <Dog id: 1>
Dog.table_name # => "dogs"
Dog # => Dog(id: integer)

Keep in mind, the table name will always be pluralized, while the class name will be singular.

Temping.create(:dogs)

Dog.table_name # => "dogs"
Dogs # => NameError: uninitialized constant Dogs

Additional database columns can be specified via the with_columns method which uses Rails migration syntax:

Temping.create(:dog) do
  with_columns do |t|
    t.string :name
    t.integer :age, :weight
  end
end

Dog.create # => <Dog id: 1, name: nil, age: nil, weight: nil>

When a block is passed to create, it is evaluated in the context of the class. This means anything you do in an ActiveRecord model class body can be accomplished in the block including method definitions, validations, module includes, etc.

Temping.create(:dog) do
  validates :name, presence: true

  with_columns do |t|
    t.string :name
    t.integer :age, :weight
  end

  def quack
    "arf!"
  end
end

Dog.create!

# => ActiveRecord::RecordInvalid: Validation failed: Name can't be blank

codey = Dog.create!(name: "Codey")
codey.quack

# => "arf!"

All attributes you pass to create_table are evaluated too. For example you can create a dog with a primary key of the type uuid (assuming you use PostgreSQL with uuid-ossp extension enabled):

Temping.create(:dog, id: :uuid, default: -> { "uuid_generate_v4()" })

Dog.create # => <Dog id: d937951b-765c-4bc9-804e-3171d22117b0>

Parent Classes

An option to specify the parent class can be given as a second parameter to Temping.create. This allows testing in environments where models inherit from a common base class.

# A custom base model class
class Vehicle < ActiveRecord::Base
  self.abstract_class = true
  
  def navigate_to(destination)
    # non-vehicle specific logic
  end
end

Temping.create(:car, parent_class: Vehicle) do
  with_columns do |t|
    t.string :name
    t.integer :num_wheels
  end
end
Temping.create(:bus, parent_class: Vehicle) do
  with_columns do |t|
    t.string :name
    t.integer :num_wheels
  end
end

my_car = Car.create
my_car.navigate_to(:home)

Namespaces

Temping supports creating models within namespaces. You can do this either by just including the full namespace in the name:

Temping.create("animal/cat")

Animal::Cat.create # => <Animal::Cat id: 1>
Animal::Cat.table_name # => "cats"
Animal::Cat # => Animal::Cat(id: integer)

Or you can create the module(s) yourself:

module Engineers
  def self.table_name_prefix
    "hard_working_"
  end
end
Temping.create("engineers/developers")

Engineers::Developer.create # => <Engineers::Developer id: 1> 
Engineers::Developer.table_name # => "hard_working_developers"
Engineers::Developer # => Engineers::Developer(id: integer)

Please note that if you create the modules yourself, Temping will NOT attempt to undefine them when you call Temping.teardown, it will only undefine the modules/models created by itself:

module Engineers; end
Temping.create("engineers/developers")
Temping.create("animal/cat")

Temping.teardown

Object.const_defined?("Engineers") # => true
Object.const_defined?("Engineers::Developer") # => false
Object.const_defined?("Animal") # => false
Object.const_defined?("Animal::Cat") # => false

Deep namespaces are supported as well:

Temping.create("continents/countries/cities/streets/buildings")

# => Continents::Countries::Cities::Streets::Building(id: integer) 

Foreign Keys

Temporary tables in MySQL cannot have foreign keys. PostgreSQL doesn't have this limitation.

If you want to use foreign keys with Temping in MySQL you might want to consider making tables permanent by overwriting temporary option when you set up a model:

Temping.create(:user, temporary: false)
Temping.create(:post, temporary: false) do
  with_columns do |t|
    t.references :user, foreign_key: true
  end
end

This however is not a recommended approach because the whole idea of Temping is about using temporary tables.

Tested Environments

The latest version of this gem is tested with the following setups:

  • MRI 3.2 with ActiveRecord 7.0
  • MRI 3.1 with ActiveRecord 7.0, 6.1
  • MRI 3.0 with ActiveRecord 7.0, 6.1
  • MRI 2.7 with ActiveRecord 7.0, 6.1, 6.0
  • MRI 2.6 with ActiveRecord 6.1, 6.0
  • MRI 2.5 with ActiveRecord 6.1, 6.0
  • MRI 2.4 with ActiveRecord 5.2
  • MRI 2.3 with ActiveRecord 5.2 (only SQLite)
  • MRI 2.2 with ActiveRecord 5.2 (only SQLite)
  • JRuby with ActiveRecord 6.1, 6.0 (with activerecord-jdbc-adapter)
  • TruffleRuby with ActiveRecord 7.0, 6.1, 6.0

with the following database systems:

  • SQLite3
  • MySQL (versions 5.5-8.0)
  • PostgreSQL (versions 10-15)

If you need to support older versions of Ruby or ActiveRecord you might have to use the older versions of this gem (3.10.0 or below).

Contributing

All contributions are welcome!

Please take a look at CONTRIBUTING.md for some tips.

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Create temporary table-backed ActiveRecord models for use in tests

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