RSpec - Testing Strong Parameters ActionController::ParameterMissing

Question

How can one test if a certain action raises an ActionController::ParameterMissing exception?

For example:

it "raises an exception" do
  post :create, {}
  expect(response).to raise ActionController::ParameterMissing
end

The above does not seem to work, it will fail the test with the ActionController::ParameterMissing exception.

Aaron K · Accepted Answer · 2013-05-23 23:19:03Z

21

Use the expect block syntax using the raise_error matcher:

it "raises an exception" do
  expect{ post(:create, {}) }.to raise_error ActionController::ParameterMissing
end

The reason that your code doesn't work is that post(:create, {}) raises the exception. This happens before the expect(response).to ... code gets executes. Since the #post message is not in a begin...end block, the raised exception is passed up to RSpec failing the test.

edited May 23, 2013 at 23:19

answered May 23, 2013 at 22:04

Aaron K

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3 Comments

Artem Kalinchuk Over a year ago

Great! Can you explain why it works with an expect block but not with the code in the question?

nonrectangular Over a year ago

The exception is raised as part of the call to post, not as part of the call to response

alex Over a year ago

Key thing here to note is that the brackets for except have changed from ( ) to { }.

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