I have a strange issue with receive_message_chain rspec 3.6
allow_any_instance_of(Order).to receive_message_chain('line_items.find')
{LineItem.first}
When i do a order.line_items instead of returning a collection it returns me a <Double (anonymous)> object which is not what i wanted.
Any suggestions??
When you tell RSpec to set receive_message_chain('line_items.find') on a specific object, it needs set the correct stubs in place for the chain to work.
First RSpec stubs the method line_items on the object. Next it needs to stub the method find, but this method needs to be stubbed on the return value of the method line_items. Since we stubbed that method, RSpec needs to come up with a some return value, that can be the target of the stubbing.
So RSpec sets the return value of the method line_items to be an anonymous double that has the the method find stubbed. Because of this once you set the receive_message_chain with 'line_items.find', the object will always return an anonymous double when line_items is called. And since you use allow_any_instance_of, this means that the method line_items is now stubbed on all the instances of Order.
I would recommend thinking about trying to remove the uses of allow_any_instance_of and receive_message_chain from your specs if it is possible, since they are really shortcuts to be used in specs if you really cannot change the design of your code. https://relishapp.com/rspec/rspec-mocks/docs/working-with-legacy-code/message-chains
However if that is not possible, you can remove the receive_message_chain and set the chain yourself.
line_items_stub = double
# or line_items_stub = Order.new.line_items
# or line_items_stub = [LineItem.new, LineItem.new]
# or line_items_stub = the object that you want
allow_any_instance_of(Order).
to receive(:line_items).
and_return(line_items_stub)
allow(line_items_stub).to receive(:find)
If you were able to remove the allow_any_instance_of you could use and_call_original to call the for real implementation of line_items on that concrete instance you are stubbing the message_chain on.
It should be straight forward, but it doesn't work for me.
I'm stubbing a function call, and I want to make sure it is called once, so I did:
MyClass.stubs(:record).returns(true).expect(:record).once
MyClass.run
but I keep getting:
expected exactly once, not yet invoked: allowed any number of times, invoked once: MyClass.record(any_parameters).record(any_parameters)
What am I doing wrong?
Are you trying to set expectations for 2 separate invocations on record?
stubs is just a syntactic sugar for expects, specifying that you expect an invocation zero or more times.
You could probably rewrite your example as such:
MyClass.expects(:record).returns(true)
Keep in mind that expects is by default implying the once part although you could add it if you think that it adds to your code's clarity.
I'm trying to make sense of the tests in an inherited app, and I need some help.
There are lots of spec groups like this one (view spec):
let(:job_post) { FactoryGirl.create(:job_post) }
# ...
before do
expect(view).to receive(:job_post).at_least(:once).and_return(job_post)
end
it "should render without error" do
render
end
... with job_post being an helper method defined on the controller. (yes, they could have used #instance variables, and I'm in the process of refactoring it).
Now, in my opinion using an expect inside a before block is wrong. Let's forget about that for a second.
Normally the test above is green.
However, if I remove the expect line, the test fails. It appears that in this case expect is stubbing the method on the view. In fact, replacing expect with allow seems to have exactly the same effect.
I think that what's going on is that normally – when run with a server – the view will call job_posts and the message will land on the helper method on the controller, which is the expected behaviour.
Here, however, expect is setting an expectation and, at the same time, stubbing a method on the view with a fixed return value. Since the view template will call that method, the test passes.
About that unexpected "stub" side effect of expect, I've found this in the rspec-mocks readme:
(...) We can also set a message expectation so that the example fails if find is not called:
person = double("person")
expect(Person).to receive(:find) { person }
RSpec replaces the method we're stubbing or mocking with its own test-double-like method. At the end of the example, RSpec verifies any message expectations, and then restores the original methods.
Does anyone have any experience with this specific use of the method?
Well, that's what expect().to receive() does! This is the (not so) new expectation syntax of rspec, which replaces the should_receive API
expect(view).to receive(:job_post).at_least(:once).and_return(job_post)
is equivalent to
view.should_receive(:job_post).at_least(:once).and_return(job_post)
and this API sets the expectation and the return value. This is the default behavior. To actually call the original method as well, you need to explicitly say so:
view.should_receive(:job_post).at_least(:once).and_call_original
On to some other issues:
(yes, they could have used #instance variables, and I'm in the process of refactoring it).
let API is very ubiquitous in rspec testing, and may be better than #instance variables in many cases (for example - it is lazy, so it runs only if needed, and it is memoized, so it runs at most once).
In fact, replacing expect with allow seems to have exactly the same effect.
The allow syntax replaces the stub method in the old rspec syntax, so yes, it has the same effect, but the difference is, that it won't fail the test if the stubbed method is not called.
As the OP requested - some explanations about should_receive - unit tests are expected to run in isolation. This means that everything which is not directly part of your test, should not be tested. This means that HTTP calls, IO reads, external services, other modules, etc. are not part of the test, and for the purpose of the test, you should assume that they work correctly.
What you should include in your tests is that those HTTP calls, IO reads, and external services are called correctly. To do that, you set message expectations - you expect the tested method to call a certain method (whose actual functionality is out of the scope of the test). So you expect the service to receive a method call, with the correct arguments, one or more times (you can explicitly expect how many times it should be called), and, in exchange for it actually being called, you stub it, and according to the test, set its return value.
Sources:
Message expectation
RSpec's New Expectation Syntax
Rspec is a meta-gem, which depends on the rspec-core, rspec-expectations and rspec-mocks gems.
Rspec-mocks is a test-double framework for rspec with support for method stubs, fakes, and message expectations on generated test-doubles and real objects alike.
allow().to receive
is the use of 'Method Stubs', however
expect().to receive
is the use of 'Message Expectations'
You can refer to the Doc for more details
If you don't want to stub as a side affect, you can always call the original.
https://relishapp.com/rspec/rspec-mocks/v/2-14/docs/message-expectations/calling-the-original-method
For example I once wanted to spy on a method, but also call the function else it has other side affects. That really helped.
https://relishapp.com/rspec/rspec-mocks/v/2-14/docs/message-expectations/calling-the-original-method
I'm seeing a very weird output from my Rails tests, using Mocha and Rails 3.1.0.
not all expectations were satisfied
unsatisfied expectations:
- expected exactly once, not yet invoked: #<GitAccess:0xbb5c344>.branches(any_parameters)
satisfied expectations:
- allowed any number of times, invoked once: #<GitAccess:0xbb5c344>.branches(any_parameters)
It says that my "branches" method was never called, but called once - on the same object? How is this possible? My controller looks like this:
def create
git_access.branches()
end
I'm totally not understanding how this is possible.
Okay, here's the answer. I somehow thought that .expects would only check whether the function is called or not. So in my test I had .expects and .stubs on the same function call, which made mocha ignore my .stubs.
By reading a bunch of tutorials online, .stubs should be used when you want to fake the response of a method, and .expects when you want to fake the response of a method AND test whether the method is called.
I'm attempting to test a class which makes use of the rails configuration file. I'd like to mock Rails::configuration.
I've tried things like
Rails::singleton_class.expects(:configuration).returns('result')
Rails::singleton_class.stubs(:configuration).returns('result')
How do I go about doing this?
Rails.expects(:configuration).returns('result')
Please note there was a typo in your example. The returned value must be passed using returns, not return.
Also note, Rails.configuration returns Rails.application.config. If your method doesn't use Rails.configuration directly, it might actually bypass the call and your expectation won't work.
Rails.stubs(:configuration).returns(Rails::Application::Configuration.allocate)
This answer on mocking a Net response
helped