RSpec clone

A minimalist RSpec clone with all the essentials.

What did you RSpec?

Status

Gem Version Documentation CI RuboCop

Project goals

  • Enforce the guidelines and best practices outlined in the community RSpec style guide.
  • Provide most of RSpec's DSL to express expected outcomes of a code example without magic power.

Some differences

  • Less features and an implementation with much less code complexity.
  • Spec files can also be executed directly with the ruby executable.
  • There is no option to activate monkey-patching.
  • It does not rely on hacks such as at_exit hook to trigger the tests.
  • Built-in matchers do not trust actual and do not send it messages.
  • If no subject has been explicitly determined, none is defined.
  • If no described class is set, described_class is undefined instead of nil.
  • Expectations cannot be added inside a before block.
  • Arbitrary helper methods are not exposed to examples.
  • The let method defines a helper method rather than a memoized helper method.
  • The one-liner is_expected syntax also works with block expectations.
  • subject, before, after and let definitions must come before examples.
  • Each context runs its tests in isolation to prevent side effects.

Important ⚠️

To avoid confusion in the community, please note that:

Note

Following RubyGems naming conventions, the module name for this project is RSpec.

Installation

Add this line to your application's Gemfile:

gem "r_spec", ">= 1.0.0.beta11"

And then execute:

bundle

Or install it yourself as:

gem install r_spec --pre

Overview

RSpec clone provides a structure for writing executable examples of how your code should behave.

Inspired by RSpec, it includes a domain specific language (DSL) that allows you to write examples in a way similar to plain english.

A basic spec looks something like this:

Super DRY example

Usage

Anatomy of a spec file

To use the RSpec module and its DSL, you need to add require "r_spec" to your spec files. Many projects use a custom spec helper which organizes these includes.

Concrete test cases are defined in it blocks. An optional descriptive string states it's purpose and a block contains the main logic performing the test.

Test cases that have been defined or outlined but are not yet expected to work can be defined using pending instead of it. They will not be run but show up in the spec report as pending.

An it block contains an example that should invoke the code to be tested and define what is expected of it. Each example can contain multiple expectations, but it should test only one specific behaviour.

To express an expectation, wrap an object or block in expect, call to (or not_to) and pass it a matcher object. If the expectation is met, code execution continues. Otherwise the example has failed and other code will not be executed.

In test files, specs are structured by example groups which are defined by describe and context sections. Typically a top level describe defines the outer unit (such as a class) to be tested by the spec. Further describe sections can be nested within the outer unit to specify smaller units under test (such as individual methods).

For unit tests, it is recommended to follow the conventions for method names:

  • outer describe is the name of the class, inner describe targets methods;
  • instance methods are prefixed with #, class methods with ..

To establish certain contexts — think empty array versus array with elements — the context method may be used to communicate this to the reader. Its behavior is slightly different from describe because each context runs its tests in isolation, so side effects caused by testing do not propagate out of contexts.

describe and context take an optional description as argument and a block containing the individual specs or nested groupings.

Expectations

Expectations define if the value being tested (actual) matches a certain value or specific criteria.

Equivalence

expect(actual).to eql(expected) # passes if expected.eql?(actual)
expect(actual).to eq(expected)  # passes if expected.eql?(actual)

Identity

expect(actual).to equal(expected) # passes if expected.equal?(actual)
expect(actual).to be(expected)    # passes if expected.equal?(actual)

Regular expressions

expect(actual).to match(expected) # passes if expected.match?(actual)

Expecting errors

expect { actual }.to raise_exception(expected) # passes if expected exception is raised

Truth

expect(actual).to be_true # passes if true.equal?(actual)

Untruth

expect(actual).to be_false # passes if false.equal?(actual)

Nil

expect(actual).to be_nil # passes if nil.equal?(actual)

Type/class

expect(actual).to be_instance_of(expected)    # passes if expected.equal?(actual.class)
expect(actual).to be_an_instance_of(expected) # passes if expected.equal?(actual.class)

Running specs

By convention, specs live in the spec/ directory of a project. Spec files should end with _spec.rb to be recognizable as such.

Depending of the project settings, you may run the specs of a project by running rake spec (see rake integration example below). A single file can also be executed directly with the Ruby interpreter.

Examples

Run all specs in files matching spec/**/*_spec.rb:

bundle exec rake spec

Run a single file:

ruby spec/my/test/file_spec.rb

I know that sounds weird, but the rspec command line is also working pretty well:

rspec spec/my/test/file_spec.rb
rspec spec/my/test/file_spec.rb:42
rspec spec/my/test/
rspec

Spec helper

Many projects use a custom spec helper file, usually named spec/spec_helper.rb.

This file is used to require r_spec and other includes, like the code from the project needed for every spec file.

rake integration example

The following Rakefile settings should be enough:

require "bundler/gem_tasks"
require "rake/testtask"

Rake::TestTask.new do |t|
  t.pattern = "spec/**/*_spec.rb"
  t.verbose = true
  t.warning = true
end

task spec: :test
task default: :test

Performance

Runtime

Benchmark against 100 executions of a file containing one expectation (lower is better).

Runtime

Test suite

RSpec clone's specifications are self-described here: spec/

Contact

Special thanks ❤️

I would like to thank the whole RSpec team for all their work. It's a great framework and it's a pleasure to work with every day.

Without RSpec, this clone would not have been possible.

Buy me a coffee ☕

If you like this project please consider making a small donation.

Donate with Ethereum

Versioning

RSpec clone follows Semantic Versioning 2.0.

License

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

One more thing

Under the hood, RSpec clone is largely animated by a collection of testing libraries designed to make programmers happy.

It's a living example of what we can do combining small libraries together that can boost the fun of programming.

Fix testing tools logo for Ruby