BetterAssertDifference

assert_difference, but better.

Installation

Add this line to your application's Gemfile:

gem 'better_assert_difference'

And then execute:

$ bundle

Or install it yourself as:

$ gem install better_assert_difference

Usage

Include BetterAssertDifference in your tests:

  # For Rails
  ActiveSupport::TestCase.include BetterAssertDifference
  # For MiniTest
  Minitest::Test.include BetterAssertDifference
  # For RSpec
  RSpec.configure do |config|
    config.include AssertDifference
  end

Backward compatible

You can use assert_difference just as usual with string expressions or procs:

  assert_difference('Foo.bar.count', 3) do
    # block omitted
  end

  assert_difference(-> { Foo.bar.count }, 2) do
    # block omitted
  end

Implicit call of count on ActiveRecord relations, arrays, etc.

Most of the time you'll want to count objects. You won't have to use string expressions or procs, just pass an ActiveRecord_Relation object or an array.

  assert_difference(Foo.where(bar: true)) do
    # block omitted
  end

Multiple differences in one call

Specify an expected difference for each expression:

  assert_difference(Foo.where(bar: true) => 3, Foo.where(baz: false) => 5) do
    # block omitted
  end

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/julien-meichelbeck/better_assert_difference.

License

The gem is available as open source under the terms of the MIT License.