aggregate_assertions

Aggregate assertions when testing using minitest. Similar to RSpec's aggregate_failures, this gem enables the reporting failures from multiple assertions in a single test.

It is possible to use rspec-expectations with minitest, but the aggregate_assertions gem adds this functionality with no dependencies beyond minitest itself when only assertions are used.

Normally a test will stop at the first false assertion. Though we might attempt to write tests with a single assertion, due to expensive setup it is often necessary, or more convenient, to make multiple assertions within a test.

Using the aggregate_assertions method from this gem with a block, all assertions from the block will be grouped and reported as a single assertion at the completion of the block. The multiple assertion error that is reported contains the messages from all the errors.

The aggregate_assertions implementation uses a thread-local variable, so assertions and other errors from different threads will still cause a test to fail immediately.

Installation

Add this line to the test group of your application's Gemfile:

group "test" do
  gem "aggregate_assertions"
end

And then execute:

$ bundle install

Or install it yourself as:

$ gem install aggregate_assertions

Usage

Use aggregate_assertions with a block in the body of a test. An optional label may be specified that will be included in any aggregated error message:

def test_response_example
  response = Struct.new(:status, :headers, :body).new(404, { "Content-Type" => "text/plain" }, "Not Found")

  aggregate_assertions("testing response") do
    assert_equal(200, response.status)
    assert_equal("application/json", response.headers["Content-Type"])
    assert_equal('{"message":"Success"}', response.body)
  end
end

The failure from this test produces the error:

Failure:
ExampleTest#test_response_example [test/test_example.rb:5]:
There were 3 errors in group "testing response":
    1) /Users/tjwp/git/aggregate_assertions/test/aggregate_assertions_test.rb:8:
      Expected: 200
        Actual: 404

    2) /Users/tjwp/git/aggregate_assertions/test/aggregate_assertions_test.rb:9:
      Expected: "application/json"
        Actual: "text/plain"

    3) /Users/tjwp/git/aggregate_assertions/test/aggregate_assertions_test.rb:10:
      Expected: "{\"message\":\"Success\"}"
        Actual: "Not Found"

Experimental: Enable for all tests

All tests in a class or an entire test suite can be implicitly wrapped with aggregate_assertions.

To enable for all tests in a class include the module AggregateAssertions::EachTest:

class MyTest < Minitest::Test
  include AggregateAssertions::EachTest

  def test_both_errors_reported
    # both assertions are reported without needing an explicit aggregate_assertions block
    assert false, "first error"
    assert false, "second error"
  end
end

To enable for all tests in a test suite require aggregate_assertions/everywhere from your test_helper.rb file.

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

To check code style, run bundle exec rubocop.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/tjwp/aggregate_assertions.

License

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