Rspec / Capybara-应该把变化变成预期

Question

In my Ruby on Rails 4.2 app, I would like to change a test checking inline style to the rspec 3 more recent "expect" on a "should" but i get an error.

When I use the test below, my test passes:

find('#zone')['style'].should == "background-image: url(xxxxx); background-size: cover;"

I tried to convert it to rspec more recent "expect"

expect('#zone')['style'].to eq("background-image: url(xxxxx); background-size: cover;")

but I get this error:

undefined method `[]' for #<RSpec::Expectations::ExpectationTarget:0x00000008578840>

How to achieve this?

Answer 1

expect(find('#zone')['style']).to eq "background-image...."

In general, something.should == is equivalent to writing expect(something).to eq

There are some subtle differences ("bug fixes", if you like) on objects that use delegated methods, or implement methods such as should themselves; but for the most part I wouldn't worry about that; you can consider the two formats equivalent, but should always aim to use the new expect format.

One other nice conversion is that if you wrote tests that use the (sometimes implicitly defined) subject variable - eg subject.should ... , you can re-write this as either: expect(subject).to , or alternatively just: is_expected.to

Answer 2

While the accepted answer is technically correct, it can potentially lead to flaky tests if you have a dynamic page. This can happen when the element where the style attribute is being checked is being updated due to a JS action, and the check can occur before the style has changed. It's much better to write the expectation as

expect(page).to have_css('#zone[style="background-image: url(xxxxx); background-size: cover;"]')

or

expect(find('#zone')).to match_css('[style="background-image: url(xxxxx); background-size: cover;"]')