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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 { }.

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. |