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Project: RSpec Expectations 2.14

equality matchers

Ruby exposes several different methods for handling equality:

a.equal?(b) # object identity - a and b refer to the same object
a.eql?(b)   # object equivalence - a and b have the same value
a == b      # object equivalence - a and b have the same value with type conversions

Note that these descriptions are guidelines but are not forced by the
language. Any object can implement any of these methods with its own
semantics.

rspec-expectations ships with matchers that align with each of these methods:

  a.should equal(b) # passes if a.equal?(b)
  a.should eql(b)   # passes if a.eql?(b)
  a.should == b     # passes if a == b

It also ships with two matchers that have more of a DSL feel to them:

  a.should be(b) # passes if a.equal?(b)
  a.should eq(b) # passes if a == b

These are a useful pair if you wish to avoid the warning that Ruby emits on
a.should == b

Scenarios
compare using eq (==)
Given
a file named "compare_using_eq.rb" with:
describe "a string" do
  it "is equal to another string of the same value" do
    "this string".should eq("this string")
  end

  it "is not equal to another string of a different value" do
    "this string".should_not eq("a different string")
  end
end

describe "an integer" do
  it "is equal to a float of the same value" do
    5.should eq(5.0)
  end
end
When
I run rspec compare_using_eq.rb
Then
the output should contain "3 examples, 0 failures"
compare using ==
Given
a file named "compare_using_==.rb" with:
describe "a string" do
  it "is equal to another string of the same value" do
    "this string".should == "this string"
  end

  it "is not equal to another string of a different value" do
    "this string".should_not == "a different string"
  end
end

describe "an integer" do
  it "is equal to a float of the same value" do
    5.should == 5.0
  end
end
When
I run rspec compare_using_==.rb
Then
the output should contain "3 examples, 0 failures"
compare using eql (eql?)
Given
a file named "compare_using_eql.rb" with:
describe "an integer" do
  it "is equal to another integer of the same value" do
    5.should eql(5)
  end

  it "is not equal to another integer of a different value" do
    5.should_not eql(6)
  end

  it "is not equal to a float of the same value" do
    5.should_not eql(5.0)
  end

end
When
I run rspec compare_using_eql.rb
Then
the output should contain "3 examples, 0 failures"
compare using equal (equal?)
Given
a file named "compare_using_equal.rb" with:
describe "a string" do
  it "is equal to itself" do
    string = "this string"
    string.should equal(string)
  end

  it "is not equal to another string of the same value" do
    "this string".should_not equal("this string")
  end

  it "is not equal to another string of a different value" do
    "this string".should_not equal("a different string")
  end

end
When
I run rspec compare_using_equal.rb
Then
the output should contain "3 examples, 0 failures"
compare using be (equal?)
Given
a file named "compare_using_be.rb" with:
describe "a string" do
  it "is equal to itself" do
    string = "this string"
    string.should be(string)
  end

  it "is not equal to another string of the same value" do
    "this string".should_not be("this string")
  end

  it "is not equal to another string of a different value" do
    "this string".should_not be("a different string")
  end

end
When
I run rspec compare_using_be.rb
Then
the output should contain "3 examples, 0 failures"

Last published 10 months ago by myronmarston.