I have code that is requesting the user for input, such as:
class Foo
def prompt_for_foobar
puts "where is the foobar?"
gets.chomp
end
end
I would like to test that my application is asking "where is the foobar?". My test will pass upon commenting out 'gets.chomp'. but that is needed and the anything else I have tried has given me a Errno::ENOENT: error.
it "should prompt user" do
console = Foo.new
request = "where is the foobar?"
expect { console.prompt_for_foobar }.to output(request).to_stdout
end
What is the best way to test this method?
Not sure if this is the best way to handle this, but you can send puts and gets to STDOUT and STDIN.
class Foo
def prompt_for_foobar
STDOUT.puts "where is the foobar?"
STDIN.gets.chomp
end
end
Then, test that STDIN receives that puts message with your desired object.
describe Foo do
let(:foo) { Foo.new }
before(:each) do
allow(STDIN).to receive(:gets) { "user input" }
end
describe "#prompt_for_foobar" do
it "prompts the user" do
expect(STDOUT).to receive(:puts).with("where is the foobar?")
foo.prompt_for_foobar
end
it "returns input from the user" do
allow(STDOUT).to receive(:puts)
expect(foo.prompt_for_foobar).to eq "user input"
end
end
end
The problem is that gets is a method that forces human interaction (at least in the context of RSpec, where stdin isn't connected to a pipe from another process), but the entire point of automated testing tools like RSpec are to be able to run tests without involving human interaction.
So, rather than relying directly on gets in your method, I recommend you rely on a collaborator object that implements a particular interface -- that way in the test environment you can provide an implementation of that interface that provides a response without human interaction, and in other environments it can use gets to provide a response. The simplest collaborator interface here is probably a proc (they're perfect for this kind of thing!), so you could do the following:
class Foo
def prompt_for_foobar(&responder)
responder ||= lambda { gets }
puts "where is the foobar?"
responder.call.chomp
end
end
RSpec.describe Foo do
it 'prompts the user to respond' do
expect { Foo.new.prompt_for_foobar { "" } }.to output(/where is the foobar/).to_stdout
end
it "returns the responder's response" do
expect(Foo.new.prompt_for_foobar { "response" }).to eq("response")
end
end
Notice that prompt_for_foobar no longer calls gets directly; instead it delegates the responsibility of getting a response to a responder collaborator. By default, if no responder is provided, it uses gets as a default implementation of a responder. In your test you can easily provide a responder that requires no human interaction simply by passing a block that returns a string.
Related
How do you test custom Bugsnag meta_data (in Ruby, with Rspec)?
The code that I want to test:
def do_something
thing_that_could_error
rescue => e
Bugsnag.notify(e) do |r|
r.meta_data = { my_extra_data: "useful info" }
end
end
The test I want to write:
context "when there's an error" do
it "calls Bugsnag with my special metadata" do
expect(Bugsnag).to receive(:notify) # TODO test meta_data values contain "my useful info"
expect do
do_something() # exception is thrown and rescued and sent to Bugsnag
end.not_to raise_error
end
end
I am using:
Ruby 2.6.6
Rspec 3.9.0
Bugsnag 6.17.0 https://rubygems.org/gems/bugsnag
The data inside of the meta_data variable is considerably more complicated than in this tiny example, which is why I want to test it. In a beautiful world, I would extract that logic to a helper and test the helper, but right now it is urgent and useful to test in situ.
I've been looking at the inside of the Bugsnag gem to figure this out (plus some Rspec-fu to capture various internal state and returned data) but at some point it's a good idea to ask the internet.
Since the metadata is complicated, I'd suggest simplifying it:
def do_something
thing_that_could_error
rescue => e
Bugsnag.notify(e) do |r|
r.meta_data = error_metadata(e, self, 'foo')
end
end
# I assumed that you'd like to pass exception and all the context
def error_metadata(e, object, *rest)
BugsnagMetadataComposer.new(e, object, *rest).metadata
end
So now you can have a separate test for BugsnagMetadataComposer where you have full control (without mocking) over how you initialize it, and test for metadata output.
Now you only have to test that BugsnagMetadataComposer is instantiated with the objects you want, metadata is called and it returns dummy hash:
let(:my_exception) { StandardError.new }
let(:mock_metadata) { Hash.new }
before do
# ensure thing_that_could_error throws `my_exception`
expect(BugsnagMetadataComposer)
.to receive(new)
.with(my_exception, subject, anything)
.and_return(mock_metadata)
end
And the hard part, ensure that metadata is assigned. To do that you can cheat a little and see how Bugsnag gem is doing it
Apparently there's something called breadcrumbs:
let(:breadcrumbs) { Bugsnag.configuration.breadcrumbs }
Which I guess has all the Bugsnag requests, last one on top, so you can do something similar to https://github.com/bugsnag/bugsnag-ruby/blob/f9c539670c448f7f129a3f8be7d412e2e824a357/spec/bugsnag_spec.rb#L36-L40
specify do
do_something()
expect(breadcrumbs.last.metadata).to eq(expected_metadata)
end
And for clarity, the whole spec would look a bit like this:
let(:my_exception) { StandardError.new }
let(:mock_metadata) { Hash.new }
before do
# ensure thing_that_could_error throws `my_exception`
expect(BugsnagMetadataComposer)
.to receive(new)
.with(my_exception, subject, anything)
.and_return(mock_metadata)
end
specify do
do_something()
expect(breadcrumbs.last.metadata).to eq(expected_metadata)
end
I'm trying to run an input validator that would rerun the method where the validator was invoked from if the input was bad. I'm aware (from a similar question) you can use the .caller method to find the name, but I'd like to simply call the method that invoked the current method (I don't need to know what it's name/class is.)
I've grossly simplified/altered my code for brevity here.
def stack(input)
if input == "A"
puts "Good job. Back to continue on the method you were just in."
else
puts "Try again. Back to the beginning of the method you were just in."
# invoke the method that called 'stack(input)' on this instance
# to prompt the user again from whatever method they came from.
# { insert brilliant code here (in this case, it'd call 'overflow') }
end
end
def overflow
p "Misc Instructions / Prompt: Type A to continue"
input = gets.chomp
stack(input)
# continuing code
end
overflow
Thx as always!
In such case, the standard way is to use catch and throw.
def stack(input)
case input
when "A"
puts "Good job. Back to continue on the method you were just in."
throw :continue
else
puts "Try again. Back to the beginning of the method you were just in."
end
end
def overflow
catch(:continue) do loop do
p "Misc Instructions / Prompt: Type A to continue"
stack(gets.chomp)
end end
# continuing code
end
Code being tested:
class Session
def initialize
#interface = Interface.new(self)
#interface.hello
end
end
class Interface
def initialize(session, out = $STDOUT)
#session = session
#out = out
end
def hello
#out.puts "hello"
end
end
Test:
describe Session do
let (:fake_stdout) {double("$STDOUT", :puts => true)}
let (:interface) {instance_double("Interface", :out => "fake_stdout")}
let (:session) { Session.new }
describe "#new" do
it "creates an instance of Session" do
expect(session).to be_an_instance_of(Session)
end
end
end
This throws private method 'puts' called for nil:NilClass. It seems it's not seeing the fake_stdout with its specified :puts as out. I tried tying it with allow(Interface).to receive(:new).with(session).and_return(interface), but that changed nothing. How do I get the tested Session class to see the double/instance double and pass the test?
I think, this is not really problem with stubbing, but the general approach. When writing your unit tests for some class, you should stick to functionality of that class and eventually to API it sees. If you're stubbing "internal" out of Interface - it's already to much for specs of Session.
What Session really sees, is Interfaces public hello method, thus Session spec, should not be aware of internal implementation of it (that it is #out.puts "hello"). The only thing you should really focus is that, the hello method has been called. On the other hand, ensuring that the put is called for hello should be described in specs for Interface.
Ufff... That's long introduction/explanation, but how to proceed then? (known as show me the code! too ;)).
Having said, that Session.new should be aware only of Interfaces hello method, it should trust it works properly, and Sessions spec should ensure that the method is called. For that, we'll use a spy. Let's get our hand dirty!
RSpec.describe Session do
let(:fake_interface) { spy("interface") }
let(:session) { Session.new }
before do
allow(Interface).to receive(:new).and_return(fake_interface)
end
describe "#new" do
it "creates an instance of Session" do
expect(session).to be_an_instance_of(Session) # this works now!
end
it "calls Interface's hello method when initialized" do
Session.new
expect(fake_interface).to have_received(:hello)
end
end
end
A test spy is a function that records arguments, return value, the value of this and exception thrown (if any) for all its calls.
This is taken from SinonJS (which is the first result when googling for "what is test spy"), but explanation is accurate.
How does this work?
Session.new
expect(fake_interface).to have_received(:hello)
First of all, we're executing some code, and after that we're asserting that expected things happened. Conceptually, we want to be sure, that during Session.new, the fake_interface have_received(:hello). That's all!
Ok, but I need another test ensuring that Interfaces method is called with specific argument.
Ok, let's test that!
Assuming the Session looks like:
class Session
def initialize
#interface = Interface.new(self)
#interface.hello
#interface.say "Something More!"
end
end
We want to test say:
RSpec.describe Session do
describe "#new" do
# rest of the code
it "calls interface's say_something_more with specific string" do
Session.new
expect(fake_interface).to have_received(:say).with("Something More!")
end
end
end
This one is pretty straightforward.
One more thing - my Interface takes a Session as an argument. How to test that the interface calls sessions method?
Let's take a look at sample implementation:
class Interface
# rest of the code
def do_something_to_session
#session.a_session_method
end
end
class Session
# ...
def another_method
#interface.do_something_to_session
end
def a_session_method
# some fancy code here
end
end
It won't be much surprise, if I say...
RSpec.describe Session do
# rest of the code
describe "#do_something_to_session" do
it "calls the a_session_method" do
Session.new.another_method
expect(fake_interface).to have_received(:do_something_to_session)
end
end
end
You should check, if Sessions another_method called interfaces do_something_to_session method.
If you test like this, you make the tests less fragile to future changes. You might change an implementation of Interface, that it doesn't rely on put any more. When such change is introduced - you have to update the tests of Interface only. Session knows only the proper method is called, but what happens inside? That's the Interfaces job...
Hope that helps! Please, take a look at another example of spy in my other answer.
Good luck!
My weakest point when it comes to coding, is using TDD & BDD methods - I tend to just write code.. but it is something that I am trying to work on.
Could anyone point out the best way to go about the following problem:
Class1:
module TempMod
class MyClass
def initalize(config)
#config = config
end
def process(xml)
if react_upon? xml.something
puts 'yeah'
else
puts 'nah'
end
end
def react_upon?(xml_code)
#code here
end
end
end
So lets say I wanted to test this class, or build it from a TDD point of view so I write my tests:
describe TempMod::MyClass do
let(:config) {double}
let(:myclass) {TempMod::MyClass.new config}
context 'Given that the xml is something we react upon' do
it 'should check that it is valid' do
myclass.process '<some><xml>here</xml></some>'
end
it 'should output yea'
end
end
How do I test that it is calling the react_upon? method. Do I even want to see it is calling it?
Is the proper way to test it, to test all the functions like the react_upon? itself independently of the other functions?
This is properly the main thing that is most confusing me with this sort of testing. Am I testing the whole class, or just individually testing the functions, and not their interactions with the other functions in that class?
Also I realize the the react_upon? might not adhere to the Single responsibility principle and I would probably move that out to its own module/class which I could test using a stub.
If anyone can shed some light on this for me that would be awesome.
edit:
describe TempMod::MyClass do
let (:valid_planning_status_xml) {
'<StatusUpdate> <TitleId>2329</TitleId> <FromStatus>Proposed</FromStatus> <ToStatus>Confirmed</ToStatus> </StatusUpdate>'
}
let(:config) { double }
let(:status_resolver) { double }
subject(:message_processor) { TempMod::MyClass.new config, status_resolver }
context 'Given that the message XML is valid' do
it 'should check the context of the message' do
expect(message_processor.process valid_planning_status_xml).to call :check_me
end
context 'Given that the message is for a planning event update' do
it 'should call something' do
pending
end
end
context 'Given that the message is for a recording job update' do
end
context 'Given that the message is for a video title update' do
end
end
end
Your question confused me a bit is this what you are asking
module TempMod
class MyClass
def initalize(config)
#config = config
end
def process(xml)
react_upon?(xml.something) ? 'yeah' : 'nah'
end
def react_upon?(xml_code)
#code here
end
end
end
Then test like
describe TempMod::MyClass do
let(:config) {double}
let(:myclass) {TempMod::MyClass.new config}
context 'Given that the xml is something we react upon' do
it "should respond to react_upon?" do
expect(myclass).to respond_to(:react_upon?)
end
it "should react_upon? valid xml" do
expect(myclass.react_upon?(YOUR VALID REACTION GOES HERE)).to be_true
end
it "should not react_upon? invalid xml" do
expect(myclass.react_upon?(YOUR INVALID REACTION GOES HERE)).to be_false
end
it "should say 'yeah' if it is valid" do
expect(myclass.process('<some><xml>here</xml></some>')).to eq('yeah')
end
it "should say 'nah' if it is invalid" do
expect(myclass.process('<some><xml>here</some>')).to eq('nah')
end
it 'should check the context of the message' do
expect(myclass).to receive(:react_upon?).with('<some><xml>here</xml></some>')
myclass.process('<some><xml>here</xml></some>')
end
end
end
Right now your tests have no expectations so I added one that expects myclass to respiond_to the react_upon? method and another that expects myclass.process(xml) to respond with a String that equals yeah.
I am printing some custom messages in my application using the puts command. However, I do not want these to be appearing in my Test Output. So, I tried a way to stub puts as shown below. But it still outputs my messages. What am I doing wrong ?
stubs(:puts).returns("") #Did not work out
Object.stubs(:puts).returns("") #Did not work out either
puts.stubs.returns "" #Not working as well
Kernel.stubs(:puts).returns "" #No luck
I am using Test::Unit
You probably need to stub it on the actual instance that calls puts. E.g. if you're calling puts in an instance method of a User class, try:
user = User.new
user.stubs(:puts)
user.some_method_that_calls_puts
This similarly applies to when you're trying to test puts in the top-level execution scope:
self.stubs(:puts)
What I would do is define a custom log method (that essentially calls puts for now) which you can mock or silence in test quite easily.
This also gives you the option later to do more with it, like log to a file.
edit: Or if you really want to stub puts, and you are calling it inside an instance method for example, you can just stub puts on the instance of that class.
Using Rails 5 + Mocha: $stdout.stubs(puts: '')
So the comments to the original post point to the answer:
Kernel.send(:define_method, :puts) { |*args| "" }
Instead of silencing all output, I would only silence output from the the particular objects that are putsing during your tests.
class TestClass
def some_method
...
puts "something"
end
end
it "should do something expected" do
TestClass.send(:define_method, :puts) { |*args| "" }
test_class.some_method.should == "abc123"
end