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Hide Defined Constant

Use hide_const to remove a constant for the duration of a test.

Hide top-level constant​

Given a file named "hide_const_spec.rb" with:

FOO = 7

RSpec.describe "hiding FOO" do
  it "can hide FOO" do
    hide_const("FOO")
    expect { FOO }.to raise_error(NameError)
  end

  it "restores the hidden constant when the example completes" do
    expect(FOO).to eq(7)
  end
end

When I run rspec hide_const_spec.rb

Then the examples should all pass.

Hide nested constant​

Given a file named "hide_const_spec.rb" with:

module MyGem
  class SomeClass
    FOO = 7
  end
end

module MyGem
  RSpec.describe SomeClass do
    it "hides the nested constant when it is fully qualified" do
      hide_const("MyGem::SomeClass::FOO")
      expect { SomeClass::FOO }.to raise_error(NameError)
    end

    it "restores the hidden constant when the example completes" do
      expect(MyGem::SomeClass::FOO).to eq(7)
    end
  end
end

When I run rspec hide_const_spec.rb

Then the examples should all pass.

Hiding undefined constant​

Given a file named "hide_const_spec.rb" with:

RSpec.describe "hiding UNDEFINED_CONSTANT" do
  it "has no effect" do
    hide_const("UNDEFINED_CONSTANT")
    expect { UNDEFINED_CONSTANT }.to raise_error(NameError)
  end

  it "is still undefined after the example completes" do
    expect { UNDEFINED_CONSTANT }.to raise_error(NameError)
  end
end

When I run rspec hide_const_spec.rb

Then the examples should all pass.