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Configuring an expectation framework

By default, RSpec is configured to include rspec-expectations for expressing desired outcomes. You can also configure RSpec to use:

  • rspec/expectations (explicitly)
  • test/unit assertions
  • minitest assertions
  • any combination of the above libraries

Note that when you do not use rspec-expectations, you must explicitly provide a description to every example. You cannot rely on the generated descriptions provided by rspec-expectations.

Default configuration uses rspec-expectations

Given a file named "example_spec.rb" with:

RSpec::Matchers.define :be_a_multiple_of do |factor|
match do |actual|
actual % factor == 0
end
end

RSpec.describe 6 do
it { is_expected.to be_a_multiple_of 3 }
end

When I run rspec example_spec.rb

Then the examples should all pass.

Configure rspec-expectations (explicitly)

Given a file named "example_spec.rb" with:

RSpec.configure do |config|
config.expect_with :rspec
end

RSpec.describe 5 do
it "is greater than 4" do
expect(5).to be > 4
end
end

When I run rspec example_spec.rb

Then the examples should all pass.

Configure test/unit assertions

Given rspec-expectations is not installed

And a file named "example_spec.rb" with:

RSpec.configure do |config|
config.expect_with :test_unit
end

RSpec.describe [1] do
it "is equal to [1]" do
assert_equal [1], [1], "expected [1] to equal [1]"
end

specify { assert_not_equal [1], [] }

it "is equal to [2] (intentional failure)" do
assert [1] == [2], "errantly expected [2] to equal [1]"
end
end

When I run rspec example_spec.rb

Then the output should match:

     (Test::Unit::AssertionFailedError|Mini(T|t)est::Assertion):
errantly expected \[2\] to equal \[1\]

And the output should contain "3 examples, 1 failure".

Configure minitest assertions

Given rspec-expectations is not installed

And a file named "example_spec.rb" with:

RSpec.configure do |config|
config.expect_with :minitest
end

RSpec.describe "Object identity" do
it "the an object is the same as itself" do
x = [1]
assert_same x, x, "expected x to be the same x"
end

specify { refute_same [1], [1] }

it "is empty (intentional failure)" do
assert_empty [1], "errantly expected [1] to be empty"
end

it "marks pending for skip method" do
skip "intentionally"
end
end

When I run rspec -b example_spec.rb

Then the output should match:

     MiniT|test::Assertion:
errantly expected \[1\] to be empty

And the output should contain "4 examples, 1 failure, 1 pending"

And the output should not contain "Warning: you should require 'minitest/autorun' instead.".

Configure rspec/expectations AND test/unit assertions

Given a file named "example_spec.rb" with:

RSpec.configure do |config|
config.expect_with :rspec, :test_unit
end

RSpec.describe [1] do
it "is equal to [1]" do
assert_equal [1], [1], "expected [1] to equal [1]"
end

it "matches array [1]" do
is_expected.to match_array([1])
end
end

When I run rspec example_spec.rb

Then the examples should all pass.

Configure rspec/expectations AND minitest assertions

Given a file named "example_spec.rb" with:

RSpec.configure do |config|
config.expect_with :rspec, :minitest
end

RSpec.describe "Object identity" do
it "two arrays are not the same object" do
refute_same [1], [1]
end

it "an array is itself" do
array = [1]
expect(array).to be array
end
end

When I run rspec example_spec.rb

Then the examples should all pass.

Configure test/unit and minitest assertions

Given rspec-expectations is not installed

And a file named "example_spec.rb" with:

RSpec.configure do |config|
config.expect_with :test_unit, :minitest
end

RSpec.describe [1] do
it "is equal to [1]" do
assert_equal [1], [1], "expected [1] to equal [1]"
end

specify { assert_not_equal [1], [] }

it "the an object is the same as itself" do
x = [1]
assert_same x, x, "expected x to be the same x"
end

specify { refute_same [1], [1] }
end

When I run rspec example_spec.rb

Then the examples should all pass.