Project: RSpec Mocks 3.9

Publisher: RSpec

Scope

All rspec-mocks constructs have a per-example lifecycle. Message expectations are verified
after each example. Doubles, method stubs, stubbed constants, etc. are all cleaned up after
each example. This ensures that each example can be run in isolation, and in any order.

It is perfectly fine to set up doubles, stubs, and message expectations in a
before(:example) hook, as that hook is executed in the scope of the example:

before(:example) do
  allow(MyClass).to receive(:foo)
end

Since before(:context) runs outside the scope of any individual example, usage of
rspec-mocks features is not supported there. You can, however, create a temporary scope in
any arbitrary context, including in a before(:context) hook, using
RSpec::Mocks.with_temporary_scope { }.

Scenarios

Cannot create doubles in a `before(:context)` hook
Use `with_temporary_scope` to create and use a double in a `before(:context)` hook
Doubles cannot be reused in another example

Cannot create doubles in a `before(:context)` hook

Given

a file named "before_context_spec.rb" with:

RSpec.describe "Creating a double in a before(:context) hook" do
  before(:context) do
    @dbl = double(:foo => 13)
  end

  it "fails before it gets to the examples" do
    expect(@dbl.foo).to eq(13)
  end
end

When

I run rspec before_context_spec.rb

Then

it should fail with:

The use of doubles or partial doubles from rspec-mocks outside of the per-test lifecycle is not supported.

Use `with_temporary_scope` to create and use a double in a `before(:context)` hook

Given

a file named "with_temporary_scope_spec.rb" with:

RSpec.describe "Creating a double in a before(:context) hook" do
  before(:context) do
    RSpec::Mocks.with_temporary_scope do
      dbl = double(:foo => 13)
      @result = dbl.foo
    end
  end

  it "allows a double to be created and used from within a with_temporary_scope block" do
    expect(@result).to eq(13)
  end
end

When

I run rspec with_temporary_scope_spec.rb

Then

the examples should all pass

Doubles cannot be reused in another example

Given

a file named "leak_test_double_spec.rb" with:

class Account
  class << self
    attr_accessor :logger
  end

  def initialize
    @balance = 0
  end

  attr_reader :balance

  def credit(amount)
    @balance += amount
    self.class.logger.log("Credited $#{amount}")
  end
end

RSpec.describe Account do
  it "logs each credit" do
    Account.logger = logger = double("Logger")
    expect(logger).to receive(:log).with("Credited $15")
    account = Account.new
    account.credit(15)
  end

  it "keeps track of the balance" do
    account = Account.new
    expect { account.credit(10) }.to change { account.balance }.by(10)
  end
end

When

I run rspec leak_test_double_spec.rb

Then

it should fail with the following output:

2 examples, 1 failure

1) Account keeps track of the balance

Failure/Error: self.class.logger.log("Credited $#{amount}")

#<Double "Logger"> was originally created in one example but has leaked into another example and can no longer be used.

Last published about 1 year ago by Jon Rowe.

Scope

RSpec Mocks settings