Many times one outcome may have two different consequences that need to be tested with a test double. For example if a network connection is successful I'd like to log a message, and also pass the resource to another object that will store it internally. On the other hand it feels unclean to put these two in one test. For example this code fails:
describe SomeClass do
let(:logger) { double('Logger') }
let(:registry) { double('Registry') }
let(:cut) { SomeClass.new }
let(:player) { Player.new }
describe "#connect" do
context "connection is successful" do
it "should log info" do
logger.should_receive(:info).with('Player connected successfully')
cut.connect player
end
it "should register player" do
registry.should_receive(:register).with(player)
cut.connect player
end
end
end
end
I could specify in each test that the function in the other one might get called, but that looks like unnecessary duplication. In that case I'd rather make this one test.
I also don't like that it's never explicit in the test that a method should NOT be called.
Does anyone know about an alternative that has an explicit 'should_not_receive' message instead of automatically rejecting calls that are not explicitly specified?
RSpec supports should_not_receive, which is equivalent to should_receive(...).exactly(0).times as discussed in this message from the original author of RSpec.
Related
I find mocking things with RSpec to be entirely problematic and I often don't know how much code to include, in terms of it being diagnostic. So I'll start with the situation I have and the code that I've isolated as causing the problem.
I have tests where I need to mock a browser. I have a mock driver I set up like this:
require "watir"
def mock_driver
browser = double("watir")
allow(browser).to receive(:is_a?).with(Watir::Browser).and_return(true)
allow(browser).to receive(:driver).and_return(true)
browser
end
The only problems I have in my test suite are these two tests:
context "an empiric driver is requested" do
it "a watir browser is provided" do
allow(Watir::Browser).to receive(:new).and_return(Empiric.browser)
Empiric.set_browser mock_driver
end
it "the requested watir browser can be shut down" do
#allow(Empiric.browser).to receive(:quit)
Empiric.quit_browser
#allow(mock_browser).to receive(:new).and_return(Empiric.browser)
#Empiric.set_browser mock_driver
end
end
(The commented out bits in the second test are on purpose to illustrate what's going on.)
With that one line in place in the second test, I get the following error on that test:
<Double "watir"> was originally created in one example but has leaked into another
example and can no longer be used. rspec-mocks' doubles are designed to only last for
one example, and you need to create a new one in each example you wish to use it for.
If I entirely comment out the first test above, that error doesn't happen so I know I've isolated the two tests that are interacting with each other.
Okay, now notice the final line of my second test that is commented out. That seems to be what the error is indicating to me. It's saying I need to create a new double in the other. Okay, so I'll change my last test:
it "the requested watir browser can be shut down" do
#allow(Empiric.browser).to receive(:quit)
Empiric.quit_browser
#allow(mock_browser).to receive(:new).and_return(Empiric.browser)
Empiric.set_browser mock_driver
end
So here I've uncommented the last line so I'm establishing the mock_driver in that test and not allowing the code to leak.
That, however, returns exactly the same error on exactly the same test.
I'm not sure if it would help to see the methods that are being called in that test, but here they are. First is set_browser:
def set_browser(app = :chrome, *args)
#browser = Watir::Browser.new(app, *args)
Empiric.browser = #browser
end
And here is quit_browser:
def quit_browser
#browser.quit
end
The fact that RSpec thought one test was "leaking" into the other made me think that perhaps my #browser instance was the problem, essentially being what's persisting between the two tests. But I don't see how to get around that. I thought that maybe if I quit the browser in the first test, that would help. So I changed the first test to this:
it "a watir browser is provided" do
Empiric.quit_browser
allow(Watir::Browser).to receive(:new).and_return(Empiric.browser)
Empiric.start_browser mock_driver
end
That, however, led to the above error being shown on both tests now.
My more likely accurate guess is that I simply don't know how to provide a mock in this context.
I think you have to use allow with the mock and not Watir::Browser.
For example, what happens if you allow the mock browser to receive whatever calls the browser would and have the it return the mock browser?
Right now you're allowing the "Watir::Browser" to receive those messages and that's returning an "Empiric.browser". Looking at your code, I understand why you put that in there but I think that might be what's screwing you up here.
Mocks in RSpec are horrible things that rarely if ever work correctly in situations like this. I would entirely recommend not using the mock_driver that you have set up. Rather, for each of your tests just do something similar to what you are doing in the mock_driver. My guess is you're including the mock driver as part of a shared context and that, too, is another thing that is very fragile in RSpec. Not recommended.
Instead you might want to use contexts to break up your tests. Then for each context block have a before block. I'm not sure if you should use before:all or before:each given that you're simulating a browser. But that way you can set up the browser in the before and tear it down in an after.
But I would recommend getting it working in each test individually first. Even if it's a lot of code duplication. Then once all tests are passing, refactor to put the browser stuff in those before/after blocks.
But, again, don't use mocks. Don't use shared contexts. It never ends well and honestly it makes your tests harder to reason about.
Given some advice from Micah, I wanted to provide an answer with a solution. I ended up doing this:
context "an empiric driver is requested" do
it "a watir browser is provided" do
allow(Watir::Browser).to receive(:new).and_return(Empiric.browser)
allow(Empiric.browser).to receive(:driver).and_return(true)
expect { Empiric.start_browser :some_browser }.not_to raise_error
end
it "the requested watir browser can be shut down" do
allow(Empiric.browser).to receive(:quit)
allow(Watir::Browser).to receive(:new).and_return(Empiric.browser)
allow(Empiric.browser).to receive(:driver).and_return(true)
expect { Empiric.quit_browser }.not_to raise_error
end
end
All of that was needed as it is or I would get some error or other. I removed my mock driver and, per Micah's suggestion, simply tried to incorporate what seemed to work. The above "contraption" is what I ended up with as the sweet spot.
This works in the sense of giving coverage of the methods in question. What was interesting was that I had to add this to my RSpec configuration:
RSpec.configure do |config|
config.mock_with :rspec do |mocks|
mocks.allow_message_expectations_on_nil = true
end
end
I needed to do this because RSpec was reporting that I was calling allowing something that was nil to receive a value.
This brought up some interesting things, if you think about it. I have a test that is clearly passing. And it adds to my code coverage. But is it actually testing the quit action on a browser? Well, not really since it was testing a quit action on something that it thought was nil.
But -- it does work. And it must be calling the lines of code in question because the code coverage, as reported my SimpleCov, indicates that the statements in question have been checked.
I'm new to Rspec, so sorry if this is a bad question. In one of the test tests I'm running, I have code which uses a random number generator to determine whether or not a method should be executed. If it cannot be executed, the method raises an error message.
So I need to write a test which continually runs the method on a small array of class objects until it no longer receives the error message. So in effect each class object will eventually successfully execute that method after a few tries.
The array has 6 items. I'm hoping that I need to loop through each one and then use a while loop which then tests whether the error message has been executed, but I haven't got a clue how. Any help gratefully appreciated.
I have something like this at the moment...
def create_planes
6.times do
plane=Plane.new
planes<<plane
end
end
it 'should land each plane' do
create_planes
i = 0
while i<planes.count
begin
airport.plane_land(planes[i])
i++
rescue
next
end
end
expect(airport.plane_count).to eq(6)
end
Generally with RSpec, you'll set up your inputs and test your outputs. You wouldn't execute until an error occurs, you'd execute a known number of lands and then check that the airport's plane changed to what you expect.
it "should maintain a list of landed planes" do
expect {
3.times { airport.plane_land Plane.new }
}.to change { airport.plane_count }.from(0).to(3)
end
Sorry if this is plain simple. i am new to ruby as well as rspec and it seems rspec is a very 'obscure' world (esp when coming from a .net background).
In my 'spec', i have:
before(:each) do
expect(File).to receive(:exist?).with("dummy.yaml").and_return (true)
end
This works fine for all my 'examples', except one where i want it to return false.
expect(File).to receive(:exist?).with("non_existent.yaml").and_return (false)
This obviously fails my test because although "non_existent.yaml" expectation was met, the "dummy.yaml" was not:
(<File (class)>).exist?("dummy.yaml")
expected: 1 time with arguments: ("dummy.yaml")
received: 0 times
So how can i do a 'Reset' on 'File.exist?' (a class method mock) before i setup the new expectation for it? (... "non_existent.yaml"..)
i googled and it yielded:
RSpec::Mocks.proxy_for(your_object).reset
but this gives me:
NoMethodError:
undefined method `proxy_for' for RSpec::Mocks:Module
I could not find anywhere in the documentation that this is how you should do it, and past behaviors goes to show that this solution might also change in the future, but apparently this is how you can currently do it:
RSpec::Mocks.space.proxy_for(your_object).reset
I would follow #BroiSatse's remark, though, and think about re-designing the tests, aiming to move the expectation from the before block. The before block is meant for setup, as you say, and the setup is a very weird place to put expectations.
I'm not sure how you came to this design, but I can suggest two possible alternatives:
If the test is trivial, and will work anyway, you should create one test with this explicit expectation, while stubbing it for the other tests:
before(:each) do
allow(File).to receive(:exist?).with("dummy.yaml").and_return (true)
end
it "asks if file exists" do
expect(File).to receive(:exist?).with("dummy.yaml").and_return (true)
# do the test...
end
If the expectation should run for every test, since what changes in each scenario is the context, you should consider using shared examples:
shared_examples "looking for dummy.yaml" do
it "asks if file exists" do
expect(File).to receive(:exist?).with("dummy.yaml").and_return (true)
# do the test...
end
end
it_behaves_like "looking for dummy.yaml" do
let(:scenario) { "something which sets the context"}
end
You might also want to ask myron if there is a more recommended/documented solution to reset mocked objects...
This worked for me to unmock a specific method from a class:
mock = RSpec::Mocks.space.proxy_for(MyClass)
mock.instance_variable_get(:#method_doubles)[:my_method].reset
Note: Same logic of
RSpec::Mocks.space.proxy_for(MyClass).reset which resets all methods
Expanding on #Uri Agassi's answer and as I answered on another similar question, I found that I could use RSpec::Mocks.space.registered? to check if a method was a mock, and RSpec::Mocks.space.proxy_for(my_mocked_var).reset to reset it's value.
Here is the example I included in my other answer:
Example: Resetting a mocked value
For example, if we wanted to reset this mock back to it's unmocked
default value, we can use the RSpec::Mocks.space.proxy_for helper to
find our mock, then reset it:
# when
# Rails.configuration.action_controller.allow_forgery_protection == false
# and
# allow(Rails.configuration.action_controller).to receive(:allow_forgery_protection).and_return(true)
RSpec::Mocks.space.registered?(Rails.configuration.action_controller)
# => true
Rails.configuration.action_controller.allow_forgery_protection
# => true
RSpec::Mocks.space.proxy_for(Rails.configuration.action_controller).reset
Rails.configuration.action_controller.allow_forgery_protection
# => false
Notice however that the even though the mock value has been reset, the
mock remains registered?:
RSpec::Mocks.space.registered?(Rails.configuration.action_controller)
# => true
When using "expect_any_instance" I had success using the following method to change the mock (e.g. our example: Putting out a Twitter post and returning a different tweet id)
expect_any_instance_of(Twitter::REST::Client).to receive(:update).and_return(Hashie::Mash.new(id: "12"))
# post tweet
RSpec::Mocks.space.verify_all
RSpec::Mocks.space.reset_all
expect_any_instance_of(Twitter::REST::Client).to receive(:update).and_return(Hashie::Mash.new(id: "12346"))
# post another tweet
I setup a mock object and told it to expect a check for nil and to return false:
status = double('status')
status.should_receive(:nil?).and_return(false)
I only expect the call to nil? to occur once, but I got an error in my rspec test, saying that status received nil? twice.
Is there a way to get rspec to show where/how each call occurred?
adding the '--backtrace' option did not work.
Try something like this:
status.should_receive(:nil?).twice { puts caller; false }
This tells rspec to allow two invocations and call the associated block each time. Thecaller method generates a full backtrace which you should be able to analyze onstdout. We also returnfalse to stay on the code-path we're testing.
If the two backtraces are hard to distinguish and you're only interested in the second (unexpected) invocation, then set up two successive expectations:
status.should_receive(:nil?).and_return(false)
status.should_receive(:nil?) { puts caller; false }
Here the double will return false on the first invocation and call the block on the second.
Reference for setting responses on expectations:
https://github.com/rspec/rspec-mocks#setting-responses
I'm implementing a service that has several different ways it can be accessed:
Using simple query parameters
With parameters encoded as a Javascript object
For some calls both GET and POST are supported, with POST being used when there is large amounts of data being sent to the service.
What's the best way to structure my RSpec tests to avoid unnecessarily repeating code, allowing me to run the same basic assertions each time?
I'm already using shared_examples to capture some comment tests for things like response code, mimetype, etc. But I'm wondering whether there are other options, particularly when I want to invoke the service using all request methods AND a range of expected inputs and outputs.
The way I would do it in this case is to specify the request as a lambda that performs it. That way I can refer to it in my shared specs and set a different one for each type of request.
I like using rspec describe blocks when its sets an expectation, in this case that a particular request method is used. The whole thing will look something like this:
describe FooController do
shared_examples_for "any request" do
it "assigns foo" do
#request.call
assigns[:foo].should == "bar"
end
it "does not change the number of bars" do
#request.should_not change(Bar, :count)
end
end
context "using GET" do
before do
#request = lambda { get "index" }
end
it_should_behave_like "any request"
end
end
An even cleaner way is to use the 'let' construct, although it may be a step too deep in rSpec magic for a novice:
describe FooController do
shared_examples_for "any request" do
it "assigns foo" do
request.call
assigns[:foo].should == "bar"
end
it "does not change the number of bars" do
request.should_not change(Bar, :count)
end
end
context "using GET" do
let(:request) { lambda { get "index" } }
it_should_behave_like "any request"
end
end