Rspec: How to Write Unit Test Case to Receive an Exception Which Is Getting Raised in Private Method

Rspec: How to test an exception is raised in private method?

try and_raise(Product::StaleObjectError.new(nil, nil))

see this question i asked a while about the same issue:

Rspec - wrong number of arguments when raising error

Rspec: Getting error while testing private method

According to the documentation for expect_any_instance_of, this will receive the class as a method argument, so you should use parenthesis instead of curly braces:

it 'test private method called' do
  expect_any_instance_of(Product).to receive(:private_method)
  ...
end

How to write rspec test case to test successful execution of a method and exception condition also?

You should use stubs or should_receive here.

case 1 (the behavior when internet connection exists):

it "should connect to gmail, if internet connection exists" do
  Gmail.should_receive(:new)
  @mail_sender = MailSender.new
  -> { @mail_sender.connect_to_gmail}.should_not raise_error
end

maybe you would like to return some object (Gmail.should_receive(:new).and_return(some_object)) and continue to work with this stubbed object

case 2 (the behavior when internet connection does not exist):

it "should raise error to gmail, if internet connection does not exist" do
  Gmail.stub(:new) { raise SocketError }
  @mail_sender = MailSender.new
  -> { @mail_sender.connect_to_gmail}.should raise_error
end

I hope this code helps you

Should I test private methods using RSpec?

You can find an in-depth discussion of that very subject in these slides from a Sandi Metz talk.

https://speakerdeck.com/skmetz/magic-tricks-of-testing-railsconf

She says that you may test-drive your private methods if you like, but that the only test that you should worry about are the ones testing the public interface. Otherwise you may be coupling too tightly to implementation.

I think the point by toch, on splitting out service and value object and putting those under tests is also a good one if you are getting nervous about complex private methods that aren't tested.

Rails 4 - How to mock the exception with custom response using rspec?

I would mock it like this:

allow(RestClient).to receive(:post).and_raise(User::APIError, 'custom error message')

See docs about mocking errors

You can then test that the exception is raised with a specific message like this.

expect { method_calling_the_API }
  .to raise_error(an_instance_of(User::APIError)
  .and having_attributes(message: 'custom error message'))

See RSpec docs for error matcher.

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