Squixtures

Squixtures is a library that provides a simple data fixtures facility, ala the fixtures generally used in unit tests. The library came about because it is quite difficult to make use of Rails fixtures outside of the Rails framework itself.

The Squixtures library makes use of the Sequel library in an attempt to attain database independence. At the moment it has only been coded for and tested with SQLite3 and Postgres. Squixtures also makes use of the LogJam library to centralize it's logging.

Installation

Add this line to your application's Gemfile:

gem 'squixtures'

And then execute:

$ bundle

Or install it yourself as:

$ gem install squixtures

Usage

Squixtures is a library so the first thing to do is to incorporated it into the file where you plan to use it. This can be done with a simple require such as the following...

require 'rubygems'
require 'squixtures'

Squixtures is based around amodule so how you deploy it will depend heavily on how you want to use it. If, for example, you only want to deploy fixtures once, when a class definition is loaded, you can use the extend statement to incorporate the functionality at the class level and then invoke the fixtures you want. For example...

class MyClass
    # Extend the class with Squixtures functionality.
    extend Squixtures::Fixtures

    # Load the fixtures required.
    fixtures :users, :accounts, :orders
end

Alternatively, if you want the fixtures reloaded regularly, say as part of the set up process for a unit test, you would include the squixtures functionality like this...

class TestMyClass
    # Incorporate the Squixtures functionality.
    include Squixtures::Fixtures

    def setup
        # Load the desired fixtures.
        fixtures :users, :accounts, :orders
    end
end

By default the Squixtures fixture loader empties the target table between fixture loads. This feature is configurable but you should be aware of it as it could cause data loss. Squixtures currently only recognises YAML style fixtures which, as an example, follow this format...

one:
    id: 1
    email: [email protected]
    password: password
    status: 1
    created_at: <%= Time.now %>
    updated_at: <%= Time.now %>

A file containing this would define a single record made up of 6 fields. The first line specifies the record name and isn't really relevant except in that it must be unique within the file that defines it. Note that the fixture files are run through ERB as part of the load process so it's possible to include simple Ruby statements into the definitions. In the example above Ruby code is used to generate values for the created_at and updated_at field values.

Advanced Usage

The Squixtures library makes a set of assumptions to attempt to ease the process of using fixtures. For example, the library assumes that a database.yml file can be found and that fixtures will be loaded into the test database specified in the database configuration. This is convenient but facilities have also been provided to work around these assumptions.

To change the database configuration entry that the library will use you can change the environment setting for Squixtures by executing a line like the following before performing any fixtures loads...

Squixtures.environment = "development"

If you want to alter the location that the Squixtures library obtains fixture files from you can do so with a line such as the following...

Squixtures.fixtures_dir = "/my/fixtures/directory"

By default Squixtures does not make use of transactions when loading fixtures. You can specifying the use of transactions on a per fixture basis with a line such as the following...

Squixtures.transactional = true

Platform Independence

The Sequel library has been used in minimize the amount of RDBMS specific code exists in the library. Unfortunately, it's impossible to be complete free of such considerations. There are two main areas where the underlying database system impinges on the code...

* Database connections. The Sequel library requires a URL like string to
  obtain a database connection. The form and content of this string are
  very much dictated by the underlying database.

* Referential integrity. Database systems which enforce strict referential
  integrity can make the injection of fixtures more difficult, especially
  in the case where the data model has circular references. This can, in
  part, be avoided by proper ordering of the fixtures load. This is not
  a complete solution however and the Squixtures library takes steps to
  deactivate relational integrity temporarily where this will alleviate
  the issue. Unfortunately the facilities for doing this are very much
  specific to the database.

At the moment the Squixtures library only supports (i.e. has been tested with) the SQLite3 and Postgres databases. Adding support for additional databases would require that the library be extended to accommodate the specified database in the areas detailed above.

The approach currently taken to this issue is to provide a database specific helper class. These helper classes provide three basic pieces of functionality. First they provide a class level function that takes a Hash of database connection configuration parameters and generates a connection URL from them. Second they provide before and after load functionality that is currently intended to be the location where referential integrity is deactivate on the appropriate table prior to the data load. There are currently two such classes defined in the library - PostgresHelper and SQLite3Helper.

Contributing

  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Added some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request