`raise_error` matcher

Use the raise_error matcher to specify that a block of code raises an error. The most basic form passes if any error is thrown:

    expect { raise StandardError }.to raise_error

You can use raise_exception instead if you prefer that wording:

    expect { 3 / 0 }.to raise_exception

raise_error and raise_exception are functionally interchangeable, so use the one that makes the most sense to you in any given context.

In addition to the basic form, above, there are a number of ways to specify details of an error/exception:

    expect { raise "oops" }.to raise_error
    expect { raise "oops" }.to raise_error(RuntimeError)
    expect { raise "oops" }.to raise_error("oops")
    expect { raise "oops" }.to raise_error(/op/)
    expect { raise "oops" }.to raise_error(RuntimeError, "oops")
    expect { raise "oops" }.to raise_error(RuntimeError, /op/)
    expect { raise "oops" }.to raise_error(an_instance_of(RuntimeError).and having_attributes(message: "oops"))

Expecting any error

Given a file named “example_spec” with:

RSpec.describe "calling a missing method" do
  it "raises" do
    expect { Object.new.foo }.to raise_error
  end
end

When I run rspec example_spec

Then the example should pass.

Expecting a specific error

Given a file named “example_spec” with:

RSpec.describe "calling a missing method" do
  it "raises" do
    expect { Object.new.foo }.to raise_error(NameError)
  end
end

When I run rspec example_spec

Then the example should pass.

Matching a message with a string

Given a file named “example_spec.rb” with:

RSpec.describe "matching error message with string" do
  it "matches the error message" do
    expect { raise StandardError, 'this message exactly'}.
      to raise_error('this message exactly')
  end
end

When I run rspec example_spec.rb

Then the example should pass.

Matching a message with a regexp

Given a file named “example_spec.rb” with:

RSpec.describe "matching error message with regex" do
  it "matches the error message" do
    expect { raise StandardError, "my message" }.
      to raise_error(/my mess/)
  end
end

When I run rspec example_spec.rb

Then the example should pass.

Matching a message with `with_message`

Given a file named “example_spec.rb” with:

RSpec.describe "matching error message with regex" do
  it "matches the error message" do
    expect { raise StandardError, "my message" }.
      to raise_error.with_message(/my mess/)
  end
end

When I run rspec example_spec.rb

Then the example should pass.

Matching a class + message with string

Given a file named “example_spec.rb” with:

RSpec.describe "matching error message with string" do
  it "matches the error message" do
    expect { raise StandardError, 'this message exactly'}.
      to raise_error(StandardError, 'this message exactly')
  end
end

When I run rspec example_spec.rb

Then the example should pass.

Matching a class + message with regexp

Given a file named “example_spec.rb” with:

RSpec.describe "matching error message with regex" do
  it "matches the error message" do
    expect { raise StandardError, "my message" }.
      to raise_error(StandardError, /my mess/)
  end
end

When I run rspec example_spec.rb

Then the example should pass.

Setting expectations on error object passed to block

Given a file named “example_spec” with:

RSpec.describe "#foo" do
  it "raises NameError" do
    expect { Object.new.foo }.to raise_error { |error|
      expect(error).to be_a(NameError)
    }
  end
end

When I run rspec example_spec

Then the example should pass.

Setting expectations on an error object with chained matchers

Given a file named “example_spec” with:

RSpec.describe "composing matchers" do
  it "raises StandardError" do
    expect { raise StandardError, "my message" }.
      to raise_error(an_instance_of(StandardError).and having_attributes({"message" => "my message"}))
  end
end

When I run rspec example_spec

Then the example should pass.

Expecting no error at all

Given a file named “example_spec” with:

RSpec.describe "#to_s" do
  it "does not raise" do
    expect { Object.new.to_s }.not_to raise_error
  end
end

When I run rspec example_spec

Then the example should pass.