TestConstruct

"This is the construct. It's our loading program. We can load anything, from clothing to equipment, weapons, and training simulations, anything we need" -- Morpheus

TestConstruct is a DSL for creating temporary files and directories during testing.

SYNOPSIS

class ExampleTest < Test::Unit::TestCase
  include TestConstruct::Helpers

  def test_example
    within_construct do |c|
      c.directory 'alice/rabbithole' do |d|
        d.file 'white_rabbit.txt', "I'm late!"

        assert_equal "I'm late!", File.read('white_rabbit.txt')
      end
    end
  end

end

Installation

Add this line to your application's Gemfile:

gem 'test_construct'

And then execute:

$ bundle

Or install it yourself as:

$ gem install test_construct

Usage

To use TestConstruct, you need to include the TestConstruct module in your class like so:

include TestConstruct::Helpers

Using construct is as simple as calling within_construct and providing a block. All files and directories that are created within that block are created within a temporary directory. The temporary directory is always deleted before within_construct finishes.

There is nothing special about the files and directories created with TestConstruct, so you can use plain old Ruby IO methods to interact with them.

Creating files

The most basic use of TestConstruct is creating an empty file with the:

within_construct do |construct|
  construct.file('foo.txt')
end

Note that the working directory is, by default, automatically changed to the temporary directory created by TestConstruct, so the following assertion will pass:

within_construct do |construct|
  construct.file('foo.txt')
  assert File.exist?('foo.txt')
end

You can also provide content for the file, either with an optional argument or using the return value of a supplied block:

within_construct do |construct|
  construct.file('foo.txt', 'Here is some content')
  construct.file('bar.txt') do
    <<-EOS
    The block will return this string, which will be used as the content.
    EOS
  end
end

If you provide block that accepts a parameter, construct will pass in the IO object. In this case, you are responsible for writing content to the file yourself - the return value of the block will not be used:

within_construct do |construct|
  construct.file('foo.txt') do |file|
    file << "Some content\n"
    file << "Some more content"
  end
end

Finally, you can provide the entire path to a file and the parent directories will be created automatically:

within_construct do |construct|
  construct.file('foo/bar/baz.txt')
end

Creating directories

It is easy to create a directory:

within_construct do |construct|
  construct.directory('foo')
end

You can also provide a block. The object passed to the block can be used to create nested files and directories (it's just a Pathname instance with some extra functionality, so you can use it to get the path of the current directory).

Again, note that the working directory is automatically changed while in the block:

within_construct do |construct|
  construct.directory('foo') do |dir|
    dir.file('bar.txt')
    assert File.exist?('bar.txt') # This assertion will pass
  end
end

Again, you can provide paths and the necessary directories will be automatically created:

within_construct do |construct|
  construct.directory('foo/bar/') do |dir|
    dir.directory('baz')
    dir.directory('bazz')
  end
end

Please read test/construct_test.rb for more examples.

Disabling chdir

In some cases, you may wish to disable the default behavior of automatically changing the current directory. For example, changing the current directory will prevent Ruby debuggers from displaying source code correctly.

If you disable, automatic chdir, note that your old assertions will not work:

within_construct(:chdir => false) do |construct|
  construct.file("foo.txt")
  # Fails. foo.txt was created in construct, but 
  # the current directory is not the construct!
  assert File.exists?("foo.txt")
end

To fix, simply use the Pathname passed to the block:

within_construct(:chdir => false) do |construct|
  construct.file("foo.txt")
  # Passes
  assert File.exists?(construct+"foo.txt")
end

Contributing

Fork it
Create your feature branch (git checkout -b my-new-feature)
Commit your changes (git commit -am 'Add some feature')
Push to the branch (git push origin my-new-feature)
Create new Pull Request