Skip to content

HTTPS clone URL

Subversion checkout URL

You can clone with HTTPS or Subversion.

Download ZIP
Provides a readable API to express expected outcomes of a code example
Ruby Cucumber Shell
tag: v3.0.0.beta2

Fetching latest commit…

Cannot retrieve the latest commit at this time

Failed to load latest commit information.
benchmarks
features
lib
script
spec
yard
.document
.gitignore
.rspec
.travis.yml
.yardopts
Changelog.md
DEV-README.md
Gemfile
Gemfile-custom.sample
Guardfile
License.txt
README.md
Rakefile
Should.md
cucumber.yml
maintenance-branch
rspec-expectations.gemspec

README.md

RSpec Expectations Build Status Code Climate

RSpec::Expectations lets you express expected outcomes on an object in an example.

expect(account.balance).to eq(Money.new(37.42, :USD))

Install

If you want to use rspec-expectations with rspec, just install the rspec gem and RubyGems will also install rspec-expectations for you (along with rspec-core and rspec-mocks):

gem install rspec

If you want to use rspec-expectations with another tool, like Test::Unit, Minitest, or Cucumber, you can install it directly:

gem install rspec-expectations

Basic usage

Here's an example using rspec-core:

describe Order do
  it "sums the prices of the items in its line items" do
    order = Order.new
    order.add_entry(LineItem.new(:item => Item.new(
      :price => Money.new(1.11, :USD)
    )))
    order.add_entry(LineItem.new(:item => Item.new(
      :price => Money.new(2.22, :USD),
      :quantity => 2
    )))
    expect(order.total).to eq(Money.new(5.55, :USD))
  end
end

The describe and it methods come from rspec-core. The Order, LineItem, Item and Money classes would be from your code. The last line of the example expresses an expected outcome. If order.total == Money.new(5.55, :USD), then the example passes. If not, it fails with a message like:

expected: #<Money @value=5.55 @currency=:USD>
     got: #<Money @value=1.11 @currency=:USD>

Built-in matchers

Equivalence

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

Note: The new expect syntax no longer supports the == matcher.

Identity

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

Comparisons

expect(actual).to be >  expected
expect(actual).to be >= expected
expect(actual).to be <= expected
expect(actual).to be <  expected
expect(actual).to be_within(delta).of(expected)

Regular expressions

expect(actual).to match(/expression/)

Note: The new expect syntax no longer supports the =~ matcher.

Types/classes

expect(actual).to be_an_instance_of(expected) # passes if actual.class == expected
expect(actual).to be_a(expected)              # passes if actual.is_a?(expected)
expect(actual).to be_an(expected)             # an alias for be_a
expect(actual).to be_a_kind_of(expected)      # another alias

Truthiness

expect(actual).to be_truthy # passes if actual is truthy (not nil or false)
expect(actual).to be true   # passes if actual == true
expect(actual).to be_falsy  # passes if actual is falsy (nil or false)
expect(actual).to be false  # passes if actual == false
expect(actual).to be_nil    # passes if actual is nil

Expecting errors

expect { ... }.to raise_error
expect { ... }.to raise_error(ErrorClass)
expect { ... }.to raise_error("message")
expect { ... }.to raise_error(ErrorClass, "message")

Expecting throws

expect { ... }.to throw_symbol
expect { ... }.to throw_symbol(:symbol)
expect { ... }.to throw_symbol(:symbol, 'value')

Yielding

expect { |b| 5.tap(&b) }.to yield_control # passes regardless of yielded args

expect { |b| yield_if_true(true, &b) }.to yield_with_no_args # passes only if no args are yielded

expect { |b| 5.tap(&b) }.to yield_with_args(5)
expect { |b| 5.tap(&b) }.to yield_with_args(Fixnum)
expect { |b| "a string".tap(&b) }.to yield_with_args(/str/)

expect { |b| [1, 2, 3].each(&b) }.to yield_successive_args(1, 2, 3)
expect { |b| { :a => 1, :b => 2 }.each(&b) }.to yield_successive_args([:a, 1], [:b, 2])

Predicate matchers

expect(actual).to be_xxx         # passes if actual.xxx?
expect(actual).to have_xxx(:arg) # passes if actual.has_xxx?(:arg)

Ranges (Ruby >= 1.9 only)

expect(1..10).to cover(3)

Collection membership

expect(actual).to include(expected)
expect(actual).to start_with(expected)
expect(actual).to end_with(expected)

expect(actual).to contain_exactly(individual, items)
# ...which is the same as:
expect(actual).to match_array(expected_array)

Examples

expect([1, 2, 3]).to include(1)
expect([1, 2, 3]).to include(1, 2)
expect([1, 2, 3]).to start_with(1)
expect([1, 2, 3]).to start_with(1, 2)
expect([1, 2, 3]).to end_with(3)
expect([1, 2, 3]).to end_with(2, 3)
expect({:a => 'b'}).to include(:a => 'b')
expect("this string").to include("is str")
expect("this string").to start_with("this")
expect("this string").to end_with("ring")
expect([1, 2, 3]).to contain_exactly(2, 3, 1)
expect([1, 2, 3]).to match_array([3, 2, 1])

should syntax

In addition to the expect syntax, rspec-expectations continues to support the should syntax:

actual.should eq expected
actual.should be > 3
[1, 2, 3].should_not include 4

See detailed information on the should syntax and its usage.

Compound Matcher Expressions

You can also create compound matcher expressions using and or or:

expect(alphabet).to start_with("a").and end_with("z")
expect(stoplight.color).to eq("red").or eq("green").or eq("yellow")

Composing Matchers

Many of the built-in matchers are designed to take matchers as arguments, to allow you to flexibly specify only the essential aspects of an object or data structure. In addition, all of the built-in matchers have one or more aliases that provide better phrasing for when they are used as arguments to another matcher.

Examples

expect { k += 1.05 }.to change { k }.by( a_value_within(0.1).of(1.0) )

expect { s = "barn" }.to change { s }
  .from( a_string_matching(/foo/) )
  .to( a_string_matching(/bar/) )

expect(["barn", 2.45]).to contain_exactly(
  a_value_within(0.1).of(2.5),
  a_string_starting_with("bar")
)

expect(["barn", "food", 2.45]).to end_with(
  a_string_matching("foo"),
  a_value > 2
)

expect(["barn", 2.45]).to include( a_string_starting_with("bar") )

expect(:a => "food", :b => "good").to include(:a => a_string_matching(/foo/))

hash = {
  :a => {
    :b => ["foo", 5],
    :c => { :d => 2.05 }
  }
}

expect(hash).to match(
  :a => {
    :b => a_collection_containing_exactly(
      a_string_starting_with("f"),
      an_instance_of(Fixnum)
    ),
    :c => { :d => (a_value < 3) }
  }
)

expect { |probe|
  [1, 2, 3].each(&probe)
}.to yield_successive_args( a_value < 2, 2, a_value > 2 )

Also see

Something went wrong with that request. Please try again.