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Project: RSpec Expectations 2.4

have(n).items matcher

RSpec provides several matchers that make it easy to set expectations about the
size of a collection. There are three basic forms:

  • collection.should have(x).items
  • collection.should have_at_least(x).items
  • collection.should have_at_most(x).items

In addition, #have_exactly is provided as an alias to #have.

These work on any collection-like object--the object just needs to respond to #size
or #length (or both). When the matcher is called directly on a collection object,
the #items call is pure syntactic sugar. You can use anything you want here. These
are equivalent:

  • collection.should have(x).items
  • collection.should have(x).things

You can also use this matcher on a non-collection object that returns a collection
from one of its methods. For example, Dir#entries returns an array, so you could
set an expectation using the following:

Dir.new("my/directory").should have(7).entries

Scenarios
have(x).items on a collection
Given
a file named "have_items_spec.rb" with:
describe [1, 2, 3] do
  it { should have(3).items }
  it { should_not have(2).items }
  it { should_not have(4).items }

  it { should have_exactly(3).items }
  it { should_not have_exactly(2).items }
  it { should_not have_exactly(4).items }

  it { should have_at_least(2).items }
  it { should have_at_most(4).items }

  # deliberate failures
  it { should_not have(3).items }
  it { should have(2).items }
  it { should have(4).items }

  it { should_not have_exactly(3).items }
  it { should have_exactly(2).items }
  it { should have_exactly(4).items }

  it { should have_at_least(4).items }
  it { should have_at_most(2).items }
end
When
I run "rspec have_items_spec.rb"
Then
the output should contain "16 examples, 8 failures"
And
the output should contain "expected target not to have 3 items, got 3"
And
the output should contain "expected 2 items, got 3"
And
the output should contain "expected 4 items, got 3"
And
the output should contain "expected at least 4 items, got 3"
And
the output should contain "expected at most 2 items, got 3"
have(x).words on a String when String#words is defined
Given
a file named "have_words_spec.rb" with:
class String
  def words
    split(' ')
  end
end

describe "a sentence with some words" do
  it { should have(5).words }
  it { should_not have(4).words }
  it { should_not have(6).words }

  it { should have_exactly(5).words }
  it { should_not have_exactly(4).words }
  it { should_not have_exactly(6).words }

  it { should have_at_least(4).words }
  it { should have_at_most(6).words }

  # deliberate failures
  it { should_not have(5).words }
  it { should have(4).words }
  it { should have(6).words }

  it { should_not have_exactly(5).words }
  it { should have_exactly(4).words }
  it { should have_exactly(6).words }

  it { should have_at_least(6).words }
  it { should have_at_most(4).words }
end
When
I run "rspec have_words_spec.rb"
Then
the output should contain "16 examples, 8 failures"
And
the output should contain "expected target not to have 5 words, got 5"
And
the output should contain "expected 4 words, got 5"
And
the output should contain "expected 6 words, got 5"
And
the output should contain "expected at least 6 words, got 5"
And
the output should contain "expected at most 4 words, got 5"

Last published over 2 years ago by dchelimsky.