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Project: RSpec Mocks 2.11

Stubbing constants

Stubbing Constants

Support is provided for stubbing constants. Like with method stubs, the
stubbed constants will be restored to their original state when an
example completes.

stub_const("Foo", fake_foo)
Foo # => fake_foo

Stubbed constant names must be fully qualified; the current module
nesting is not considered.

module MyGem
  class SomeClass; end

module MyGem
  describe "Something" do
    let(:fake_class) { Class.new }

    it "accidentally stubs the wrong constant" do
      # this stubs ::SomeClass (in the top-level namespace),
      # not MyGem::SomeClass like you probably mean.
      stub_const("SomeClass", fake_class)

    it "stubs the right constant" do
      stub_const("MyGem::SomeClass", fake_class)

When you stub a constant that is a module or a class, nested
constants on the original module or class are not transferred
by default, but you can use the :transfer_nested_constants
option to tell rspec-mocks to transfer them:

class CardDeck
  SUITS = [:Spades, :Diamonds, :Clubs, :Hearts]
  NUM_CARDS = 52

fake_class = Class.new
stub_const("CardDeck", fake_class)
CardDeck # => fake_class
CardDeck::SUITS # => raises uninitialized constant error
CardDeck::NUM_CARDS # => raises uninitialized constant error

stub_const("CardDeck", fake_class, :transfer_nested_constants => true)
CardDeck::SUITS # => [:Spades, :Diamonds, :Clubs, :Hearts]
CardDeck::NUM_CARDS # => 52

stub_const("CardDeck", fake_class, :transfer_nested_constants => [:SUITS])
CardDeck::SUITS # => [:Spades, :Diamonds, :Clubs, :Hearts]
CardDeck::NUM_CARDS # => raises uninitialized constant error


  1. Stub Defined Constant
  2. Stub Undefined Constant

Last published over 7 years ago by .