RSpec Help

Expectation framework integration

Configure 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.Scenarios

Creating an Rspec matcher

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

Configure rspec-expectations (explicitly)

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

WhenI run rspec example_spec.rb

Configure test/unit assertions

In this example, rspec-expectations is not installed

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

The second expectation fails.

Configure minitest assertions

rspec-expectations is not installed. Here, we’re using Mintest-style expectations instead of Rspec.

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

rspec -b example_spec.rb

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

“4 examples, 1 failure, 1 pending”

“Warning: you should require ‘minitest/autorun’ instead.”

Configure rspec/expectations AND test/unit assertions

example_spec.rb

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

Configure rspec/expectations AND minitest assertions

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

Configure test/unit and minitest assertions

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

Aggregating Failures

RSpec::Expectations provides aggregate_failures, an API that allows you to group a set of expectations and see all the failures at once, rather than it aborting on the first failure. RSpec::Core improves on this feature in a couple of ways:

  • RSpec::Core provides much better failure output, adding code snippets and backtraces to the sub-failures, just like it does for any normal failure.
  • RSpec::Core provides metadata integration for this feature. Each example that is tagged with :aggregate_failures will be wrapped in an aggregate_failures block. You can also use config.define_derived_metadata to apply this to every example automatically.

The metadata form is quite convenient but may not work well for end-to-end tests with multiple steps. For example, consider a spec for an HTTP client workflow that (1) makes a request, (2) expects a redirect, (3) follows the redirect, and (4) expects a particular response. You probably want the expect(response.status).to be_between(300, 399) expectation to immediately abort if it fails, because you can’t perform the next step (following the redirect) if that is not satisfied. For these situations, we encourage you to use the aggregate_failures block form to wrap each set of expectations that represents a distinct step in the test workflow.

lib/client.rb

Response = Struct.new(:status, :headers, :body)

class Client
  def self.make_request(url='/')
    Response.new(404, { "Content-Type" => "text/plain" }, "Not Found")
  end
end

Use `aggregate_failures` block form

spec/use_block_form_spec.rb

require 'client'

RSpec.describe Client do
  after do
    # this should be appended to failure list
    expect(false).to be(true), "after hook failure"
  end

  around do |ex|
    ex.run
    # this should also be appended to failure list
    expect(false).to be(true), "around hook failure"
  end

  it "returns a successful response" do
    response = Client.make_request

    aggregate_failures "testing response" do
      expect(response.status).to eq(200)
      expect(response.headers).to include("Content-Type" => "application/json")
      expect(response.body).to eq('{"message":"Success"}')
    end
  end
end
Failures:

  1) Client returns a successful response
     Got 3 failures:

     1.1) Got 3 failures from failure aggregation block "testing response".
          # ./spec/use_block_form_spec.rb:18
          # ./spec/use_block_form_spec.rb:10

          1.1.1) Failure/Error: expect(response.status).to eq(200)

                   expected: 200
                        got: 404

                   (compared using ==)
                 # ./spec/use_block_form_spec.rb:19

          1.1.2) Failure/Error: expect(response.headers).to include("Content-Type" => "application/json")
                   expected {"Content-Type" => "text/plain"} to include {"Content-Type" => "application/json"}
                   Diff:
                   @@ -1 +1 @@
                   -"Content-Type" => "application/json",
                   +"Content-Type" => "text/plain",
                 # ./spec/use_block_form_spec.rb:20

          1.1.3) Failure/Error: expect(response.body).to eq('{"message":"Success"}')

                   expected: "{\"message\":\"Success\"}"
                        got: "Not Found"

                   (compared using ==)
                 # ./spec/use_block_form_spec.rb:21

     1.2) Failure/Error: expect(false).to be(true), "after hook failure"
            after hook failure
          # ./spec/use_block_form_spec.rb:6
          # ./spec/use_block_form_spec.rb:10

     1.3) Failure/Error: expect(false).to be(true), "around hook failure"
            around hook failure
          # ./spec/use_block_form_spec.rb:12

Use `aggregate_failures` block form

require 'client'

RSpec.describe Client do
  after do
    # this should be appended to failure list
    expect(false).to be(true), "after hook failure"
  end

  around do |ex|
    ex.run
    # this should also be appended to failure list
    expect(false).to be(true), "around hook failure"
  end

  it "returns a successful response" do
    response = Client.make_request

    aggregate_failures "testing response" do
      expect(response.status).to eq(200)
      expect(response.headers).to include("Content-Type" => "application/json")
      expect(response.body).to eq('{"message":"Success"}')
    end
  end
end

Failures:

  1) Client returns a successful response
     Got 3 failures:

     1.1) Got 3 failures from failure aggregation block "testing response".
          # ./spec/use_block_form_spec.rb:18
          # ./spec/use_block_form_spec.rb:10

          1.1.1) Failure/Error: expect(response.status).to eq(200)

                   expected: 200
                        got: 404

                   (compared using ==)
                 # ./spec/use_block_form_spec.rb:19

          1.1.2) Failure/Error: expect(response.headers).to include("Content-Type" => "application/json")
                   expected {"Content-Type" => "text/plain"} to include {"Content-Type" => "application/json"}
                   Diff:
                   @@ -1,2 +1,2 @@
                   -"Content-Type" => "application/json",
                   +"Content-Type" => "text/plain",
                 # ./spec/use_block_form_spec.rb:20

          1.1.3) Failure/Error: expect(response.body).to eq('{"message":"Success"}')

                   expected: "{\"message\":\"Success\"}"
                        got: "Not Found"

                   (compared using ==)
                 # ./spec/use_block_form_spec.rb:21

     1.2) Failure/Error: expect(false).to be(true), "after hook failure"
            after hook failure
          # ./spec/use_block_form_spec.rb:6
          # ./spec/use_block_form_spec.rb:10

     1.3) Failure/Error: expect(false).to be(true), "around hook failure"
            around hook failure
          # ./spec/use_block_form_spec.rb:12

Use `:aggregate_failures` metadata

spec/use_metadata_spec.rb

require 'client'

RSpec.describe Client do
  it "follows a redirect", :aggregate_failures do
    response = Client.make_request

    expect(response.status).to eq(302)
    expect(response.body).to eq('{"message":"Redirect"}')

    redirect_response = Client.make_request(response.headers.fetch('Location'))

    expect(redirect_response.status).to eq(200)
    expect(redirect_response.body).to eq('{"message":"OK"}')
  end
end
Failures:

  1) Client follows a redirect
     Got 2 failures and 1 other error:

     1.1) Failure/Error: expect(response.status).to eq(302)

            expected: 302
                 got: 404

            (compared using ==)
          # ./spec/use_metadata_spec.rb:7

     1.2) Failure/Error: expect(response.body).to eq('{"message":"Redirect"}')

            expected: "{\"message\":\"Redirect\"}"
                 got: "Not Found"

            (compared using ==)
          # ./spec/use_metadata_spec.rb:8

     1.3) Failure/Error: redirect_response = Client.make_request(response.headers.fetch('Location'))
          KeyError:
            key not found: "Location"
          # ./spec/use_metadata_spec.rb:10
          # ./spec/use_metadata_spec.rb:10
  • @skip-when-diff-lcs-1.3

Enable failure aggregation globally using `define_derived_metadata`

require 'client'

RSpec.configure do |c|
  c.define_derived_metadata do |meta|
    meta[:aggregate_failures] = true
  end
end

RSpec.describe Client do
  it "returns a successful response" do
    response = Client.make_request

    expect(response.status).to eq(200)
    expect(response.headers).to include("Content-Type" => "application/json")
    expect(response.body).to eq('{"message":"Success"}')
  end
end
Failures:

  1) Client returns a successful response
     Got 3 failures:

     1.1) Failure/Error: expect(response.status).to eq(200)

            expected: 200
                 got: 404

            (compared using ==)
          # ./spec/enable_globally_spec.rb:13

     1.2) Failure/Error: expect(response.headers).to include("Content-Type" => "application/json")
            expected {"Content-Type" => "text/plain"} to include {"Content-Type" => "application/json"}
            Diff:
            @@ -1 +1 @@
            -"Content-Type" => "application/json",
            +"Content-Type" => "text/plain",
          # ./spec/enable_globally_spec.rb:14

     1.3) Failure/Error: expect(response.body).to eq('{"message":"Success"}')

            expected: "{\"message\":\"Success\"}"
                 got: "Not Found"

            (compared using ==)
          # ./spec/enable_globally_spec.rb:15

Enable failure aggregation globally using `define_derived_metadata`

spec/enable_globally_spec.rb

require 'client'

RSpec.configure do |c|
  c.define_derived_metadata do |meta|
    meta[:aggregate_failures] = true
  end
end

RSpec.describe Client do
  it "returns a successful response" do
    response = Client.make_request

    expect(response.status).to eq(200)
    expect(response.headers).to include("Content-Type" => "application/json")
    expect(response.body).to eq('{"message":"Success"}')
  end
end
Failures:

  1) Client returns a successful response
     Got 3 failures:

     1.1) Failure/Error: expect(response.status).to eq(200)

            expected: 200
                 got: 404

            (compared using ==)
          # ./spec/enable_globally_spec.rb:13

     1.2) Failure/Error: expect(response.headers).to include("Content-Type" => "application/json")
            expected {"Content-Type" => "text/plain"} to include {"Content-Type" => "application/json"}
            Diff:
            @@ -1,2 +1,2 @@
            -"Content-Type" => "application/json",
            +"Content-Type" => "text/plain",
          # ./spec/enable_globally_spec.rb:14

     1.3) Failure/Error: expect(response.body).to eq('{"message":"Success"}')

            expected: "{\"message\":\"Success\"}"
                 got: "Not Found"

            (compared using ==)
          # ./spec/enable_globally_spec.rb:15

Nested failure aggregation works

spec/nested_failure_aggregation_spec.rb

require 'client'

RSpec.describe Client do
  it "returns a successful response", :aggregate_failures do
    response = Client.make_request

    expect(response.status).to eq(200)

    aggregate_failures "testing headers" do
      expect(response.headers).to include("Content-Type" => "application/json")
      expect(response.headers).to include("Content-Length" => "21")
    end

    expect(response.body).to eq('{"message":"Success"}')
  end
end
Failures:

  1) Client returns a successful response
     Got 3 failures:

     1.1) Failure/Error: expect(response.status).to eq(200)

            expected: 200
                 got: 404

            (compared using ==)
          # ./spec/nested_failure_aggregation_spec.rb:7

     1.2) Got 2 failures from failure aggregation block "testing headers".
          # ./spec/nested_failure_aggregation_spec.rb:9

          1.2.1) Failure/Error: expect(response.headers).to include("Content-Type" => "application/json")
                   expected {"Content-Type" => "text/plain"} to include {"Content-Type" => "application/json"}
                   Diff:
                   @@ -1 +1 @@
                   -"Content-Type" => "application/json",
                   +"Content-Type" => "text/plain",
                 # ./spec/nested_failure_aggregation_spec.rb:10

          1.2.2) Failure/Error: expect(response.headers).to include("Content-Length" => "21")
                   expected {"Content-Type" => "text/plain"} to include {"Content-Length" => "21"}
                   Diff:
                   @@ -1 +1 @@
                   -"Content-Length" => "21",
                   +"Content-Type" => "text/plain",
                 # ./spec/nested_failure_aggregation_spec.rb:11

     1.3) Failure/Error: expect(response.body).to eq('{"message":"Success"}')

            expected: "{\"message\":\"Success\"}"
                 got: "Not Found"

            (compared using ==)
          # ./spec/nested_failure_aggregation_spec.rb:14

Nested failure aggregation works

require 'client'

RSpec.describe Client do
  it "returns a successful response", :aggregate_failures do
    response = Client.make_request

    expect(response.status).to eq(200)

    aggregate_failures "testing headers" do
      expect(response.headers).to include("Content-Type" => "application/json")
      expect(response.headers).to include("Content-Length" => "21")
    end

    expect(response.body).to eq('{"message":"Success"}')
  end
end
Failures:

  1) Client returns a successful response
     Got 3 failures:

     1.1) Failure/Error: expect(response.status).to eq(200)

            expected: 200
                 got: 404

            (compared using ==)
          # ./spec/nested_failure_aggregation_spec.rb:7

     1.2) Got 2 failures from failure aggregation block "testing headers".
          # ./spec/nested_failure_aggregation_spec.rb:9

          1.2.1) Failure/Error: expect(response.headers).to include("Content-Type" => "application/json")
                   expected {"Content-Type" => "text/plain"} to include {"Content-Type" => "application/json"}
                   Diff:
                   @@ -1,2 +1,2 @@
                   -"Content-Type" => "application/json",
                   +"Content-Type" => "text/plain",
                 # ./spec/nested_failure_aggregation_spec.rb:10

          1.2.2) Failure/Error: expect(response.headers).to include("Content-Length" => "21")
                   expected {"Content-Type" => "text/plain"} to include {"Content-Length" => "21"}
                   Diff:
                   @@ -1,2 +1,2 @@
                   -"Content-Length" => "21",
                   +"Content-Type" => "text/plain",
                 # ./spec/nested_failure_aggregation_spec.rb:11

     1.3) Failure/Error: expect(response.body).to eq('{"message":"Success"}')

            expected: "{\"message\":\"Success\"}"
                 got: "Not Found"

            (compared using ==)
          # ./spec/nested_failure_aggregation_spec.rb:14

Mock expectation failures are aggregated as well

require 'client'

RSpec.describe "Aggregating Failures", :aggregate_failures do
  it "has a normal expectation failure and a message expectation failure" do
    client = double("Client")
    expect(client).to receive(:put).with("updated data")
    allow(client).to receive(:get).and_return(Response.new(404, {}, "Not Found"))

    response = client.get
    expect(response.status).to eq(200)
  end
end

Failures:

  1) Aggregating Failures has a normal expectation failure and a message expectation failure
     Got 2 failures:

     1.1) Failure/Error: expect(response.status).to eq(200)

            expected: 200
                 got: 404

            (compared using ==)
          # ./spec/mock_expectation_failure_spec.rb:10

     1.2) Failure/Error: expect(client).to receive(:put).with("updated data")
            (Double "Client").put("updated data")
                expected: 1 time with arguments: ("updated data")
                received: 0 times
          # ./spec/mock_expectation_failure_spec.rb:6

Pending integrates properly with aggregated failures

require 'client'

RSpec.describe Client do
  it "returns a successful response", :aggregate_failures do
    pending "Not yet ready"
    response = Client.make_request

    expect(response.status).to eq(200)
    expect(response.headers).to include("Content-Type" => "application/json")
    expect(response.body).to eq('{"message":"Success"}')
  end
end

rspec spec/pending_spec.rb

When it runs, Rspec will list all the pending examples:

Pending: (Failures listed here are expected and do not affect your suite's status)

  1) Client returns a successful response
     # Not yet ready
     Got 3 failures:

     1.1) Failure/Error: expect(response.status).to eq(200)

            expected: 200
                 got: 404

            (compared using ==)
          # ./spec/pending_spec.rb:8

     1.2) Failure/Error: expect(response.headers).to include("Content-Type" => "application/json")
            expected {"Content-Type" => "text/plain"} to include {"Content-Type" => "application/json"}
            Diff:
            @@ -1 +1 @@
            -"Content-Type" => "application/json",
            +"Content-Type" => "text/plain",
          # ./spec/pending_spec.rb:9

     1.3) Failure/Error: expect(response.body).to eq('{"message":"Success"}')

            expected: "{\"message\":\"Success\"}"
                 got: "Not Found"

            (compared using ==)
          # ./spec/pending_spec.rb:10

Pending integrates properly with aggregated failures

require 'client'

RSpec.describe Client do
  it "returns a successful response", :aggregate_failures do
    pending "Not yet ready"
    response = Client.make_request

    expect(response.status).to eq(200)
    expect(response.headers).to include("Content-Type" => "application/json")
    expect(response.body).to eq('{"message":"Success"}')
  end
end

Pending: (Failures listed here are expected and do not affect your suite's status)

  1) Client returns a successful response
     # Not yet ready
     Got 3 failures:

     1.1) Failure/Error: expect(response.status).to eq(200)

            expected: 200
                 got: 404

            (compared using ==)
          # ./spec/pending_spec.rb:8

     1.2) Failure/Error: expect(response.headers).to include("Content-Type" => "application/json")
            expected {"Content-Type" => "text/plain"} to include {"Content-Type" => "application/json"}
            Diff:
            @@ -1,2 +1,2 @@
            -"Content-Type" => "application/json",
            +"Content-Type" => "text/plain",
          # ./spec/pending_spec.rb:9

     1.3) Failure/Error: expect(response.body).to eq('{"message":"Success"}')

            expected: "{\"message\":\"Success\"}"
                 got: "Not Found"

            (compared using ==)
          # ./spec/pending_spec.rb:10

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