Stub unimplemented method in rspec - ruby-on-rails

I'm testing my module and I decided to test it versus anonymous class:
subject(:klass) { Class.new { include MyModule } }
MyModule uses method name inside klass. To let my specs work I need to stub this method name (which is unimplemented). So I wrote:
subject { klass.new }
allow(subject).to receive(:name).and_return('SOreadytohelp') }
but it raises:
RSpec::Mocks::MockExpectationError: #<#<Class:0x007feb67a17750>:0x007feb67c7adf8> does not implement: name
from spec-support-3.3.0/lib/rspec/support.rb:86:in `block in <module:Support>'
how to stub this method without defining it?

RSpec raises this exception because it is not useful to stub a method that does not exist on the original object.
Mocking methods is always error-prone because the mock might behave differently than the original implementation and therefore specs might be successful even if the original implementation would have returned an error (or does not even exist). Allowing to mock non-existing methods is just plain wrong.
Therefore I would argue that you should not try to bypass this exception. Just add a name method to your class that raises a clear exception if run outside of the test environment:
def self.name
raise NoMethodError # TODO: check specs...
end

subject(:klass) do
Struct.new(:name) do
include MyModule
end
end
http://ruby-doc.org/core-2.2.0/Struct.html

I think that if the test you're writing is focused on your MyModule module, and that module relies on an instance method in the class that it is mixed into, then I think that method should be mocked out in the anonymous class that you use when testing the module. For example:
module MyModule
def call_name
# expected implementation of #name to be
# in the class this module is mixed into
name
end
end
RSpec.describe MyModule do
let(:my_module_able) do
Class.new do
include MyModule
# We don't care what the return value of this method is;
# we just need this anonymous class to respond to #name
def name
'Some Name that is not SOReadytohelp'
end
end.new
end
describe '#call_name' do
let(:name) { 'SOReadytohelp' }
before do
allow(my_module_able).to receive(:name).and_return(name)
end
it 'returns the name' do
expect(my_module_able.call_name).to eq(name)
end
end
end

Related

RSpec - mock a private class method call inside a request spec?

This is my class
class MyClass
def run
to_be_mocked("arg")
## etc
end
private
def to_be_mocked(arg)
# implementation
end
end
and my Controller, which is what I am writing the request specs for, call this class.
This are my request specs:
context "Some context" do
context "some sub context" do
before :each do
allow(MyClass). to receive(: to_be_mocked).with(account.url).and_return(false)
end
it "responds with a 200" do
do_request
expect(JSON.parse(response.body)["field"]).to eq true
expect(response.status).to eq 200
end
end
However my mocking fails with an MyClass does not implement: to_be_mocked
Already tried removing the private keyword, but got the same results.
What am I missing here?
You're mocking on the class, which is how you mock you "static" class-level methods. For example, if your method was def self.foo and you called it via MyClass.foo, then allow(MyClass) is the way to go.
Your method is not a class-level method, it's an instance method. You invoke it by first creating an instead of MyClass and then calling the method on that instance. You need to use allow_any_instance_of to mock the method for all future instances of the class:
allow_any_instance_of(MyClass).to receive(....)

Calling rspec methods from different file

I am trying to write a class in my code to wrap some of the RSpec calls. However, whenever I try to access rspec things, my class simply doesn't see the methods.
I have the following file defined in spec/support/helper.rb
require 'rspec/mocks/standalone'
module A
class Helper
def wrap_expect(dbl, func, args, ret)
expect(dbl).to receive(func).with(args).and_return(ret)
end
end
end
I get a NoMethodError: undefined method 'expect', despite requiring the correct module. Note that if I put calls to rspec functions before the module, everything is found correctly.
I've tried adding the following like to my spec_helper.rb:
config.requires << 'rspec/mocks/standalone'
But to no avail.
I managed to use class variables in my class and passing the functions through from the global context, but that solution seems quite extreme. Also I was able to pass in the test context itself and storing it, but I'd rather not have to do that either.
expect functions by default is associated with only rspec-core methods like it before . If you need to have expect inside a method, you can try adding the Rspec matcher class in the helper file.
include RSpec::Matchers
that error because the self which call expect is not the current rspec context RSpec::ExampleGroups, you could check by log the self
module A
class Helper
def wrap_expect(dbl, func, args, ret)
puts self
expect(dbl).to receive(func).with(args).and_return(ret)
end
end
end
# test case
A::Helper.new.wrap_expect(...) # log self: A::Helper
so obviously, A::Helper does not support expect
now you have 2 options to build a helper: (1) a module or (2) a class which init with the current context of test cases:
(1)
module WrapHelper
def wrap_expect(...)
puts self # RSpec::ExampleGroups::...
expect(...).to receive(...)...
end
end
# test case
RSpec.describe StackOverFlow, type: :model do
include WrapHelper
it "...." do
wrap_expect(...) # call directly
end
end
(2)
class WrapHelper
def initialize(spec)
#spec = spec
end
def wrap_expect(...)
puts #spec # RSpec::ExampleGroups::...
#spec.expect(...).to #spec.receive(...)...
end
end
# test case
RSpec.describe StackOverFlow, type: :model do
let!(:helper) {WrapHelper.new(self)}
it "...." do
helper.wrap_expect(...)
end
end

Rspec private method can't access class instance variable?

I am testing my class' initialize method. It calls a private method, and for some reason that method is failing.
Class (code simplified for brevity):
class MyClass
#configs = {}
def initialize(configs)
#configs = configs
check_configs
create_client
end
private
def check_configs
if #configs['some_token'].nil?
Rails.logger.git_loader.error('log message')
raise AnError
end
end
end
The test:
describe '#initialize' do
let(:config) { my_token: '123-FakeToken' }
let(:loader) { described_class.new(config) }
context 'when initialized with a set of configs' do
it { expect(loader.instance_variable_get(:#configs)).to eq(configs)}
end
end
When I put a puts before the nil? check, the token prints out nothing, though when my rake task calls the initialize method, it prints fine.
Your example is a bit confusing due to the various spelling errors in your attempt to generalize your problem. I created the following two files, and the specs ran just fine. Might be a naming error that you're experiencing and not an actual rspec problem.
# test_spec.rb
require 'rspec'
require_relative 'my_class'
describe MyClass do
describe '#initialize' do
let(:configs) { {some_token: '123-FakeToken'} }
let(:loader) { described_class.new(configs) }
context 'when initialized with a set of configs' do
it { expect(loader.instance_variable_get(:#configs)).to eq(configs)}
end
end
end
and
# my_class.rb
class MyClass
##configs = {}
def initialize(configs)
#configs = configs
check_configs
end
private
def check_configs
if #configs[:some_token].nil?
puts "log message"
raise 'an error'
end
end
end
That said, the bigger question is what are you trying to accomplish with your tests?
Testing private variables is a smell. Ideally, in the case of config variables, they will cause an effect in your instance when set. For example MyClass.foo will behave differently based on whether some_token is set or not. Testing whether the behaviour of foo changes with a some_token present or not is a high value test that you want. Instead of a low value test of whether you wrote #configs = configs correctly.
Because you made your method check_configs in a private scope, you're unable to access it from the initialize method because the object you're initializing is looking for a method that is essentially hidden to the class. You either need to make the method public or rework your initialize method to not include private methods.
note, I came back and noticed this was not clear enough.
Initialize methods are always public, therefore they cannot include any private scoping within the method. You could call a private method anywhere else within the class except the initialize method
http://en.wikibooks.org/wiki/Ruby_Programming/Syntax/Classes#Private

Mocking/stubbing a method that's included from "instance.extend(DecoratorModule)"

I use a decorator module that get's included in a model instance (through the "extends" method). So for example :
module Decorator
def foo
end
end
class Model < ActiveRecord::Base
end
class ModelsController < ApplicationController
def bar
#model = Model.find(params[:id])
#model.extend(Decorator)
#model.foo
end
end
Then I would like in the tests to do the following (using Mocha) :
test "bar" do
Model.any_instance.expects(:foo).returns("bar")
get :bar
end
Is this possible somehow, or do you have in mind any other way to get this functionality???
Just an Assumption Note: I will assume that your Decorator foo method returns "bar" which is not shown in the code that you sent. If I do not assume this, then expectations will fail anyway because the method returns nil and not "bar".
Assuming as above, I have tried the whole story as you have it with a bare brand new rails application and I have realized that this cannot be done. This is because the method 'foo' is not attached to class Model when the expects method is called in your test.
I came to this conclusion trying to follow the stack of called methods while in expects. expects calls stubs in Mocha::Central, which calls stubs in Mocha::ClassMethod, which calls *hide_original_method* in Mocha::AnyInstanceMethod. There, *hide_original_method* does not find any method to hide and does nothing. Then Model.foo method is not aliased to the stubbed mocha method, that should be called to implement your mocha expectation, but the actual Model.foo method is called, the one that you dynamically attach to your Model instance inside your controller.
My answer is that it is not possible to do it.
It works (confirmed in a test application with render :text)
I usually include decorators (instead of extending them at runtime) and I avoid any_instance since it's considered bad practice (I mock find instead).
module Decorators
module Test
def foo
"foo"
end
end
end
class MoufesController < ApplicationController
def bar
#moufa = Moufa.first
#moufa.extend(Decorators::Test)
render :text => #moufa.foo
end
end
require 'test_helper'
class MoufesControllerTest < ActionController::TestCase
# Replace this with your real tests.
test "bar" do
m = Moufa.first
Moufa.expects(:find).returns(m)
m.expects(:foo).returns("foobar")
get :bar, {:id => 32}
assert_equal #response.body, "foobar"
end
end
Ok, now I understand. You want to stub out a call to an external service. Interesting that mocha doesn't work with extend this way. Besides what is mentioned above, it seems to be because the stubbed methods are defined on the singleton class, not the module, so don't get mixed in.
Why not something like this?
test "bar" do
Decorator = Module.new{ def foo; 'foo'; end }
get :bar
end
If you'd rather not get the warnings about Decorator already being defined -- which is a hint that there's some coupling going on anyway -- you can inject it:
class ModelsController < ApplicationController
class << self
attr_writer :decorator_class
def decorator_class; #decorator_class ||= Decorator; end
end
def bar
#model = Model.find(params[:id])
#model.extend(self.class.decorator_class)
#model.foo
end
end
which makes the test like:
test "bar" do
dummy = Module.new{ def foo; 'foo'; end }
ModelsController.decorator_class = dummy
get :bar
end
Of course, if you have a more complex situation, with multiple decorators, or decorators defining multiple methods, this may not work for you.
But I think it is better than stubbing the find. You generally don't want to stub your models in an integration test.
One minor change if you want to test the return value of :bar -
test "bar" do
Model.any_instance.expects(:foo).returns("bar")
assert_equal "bar", get(:bar)
end
But if you are just testing that a model instance has the decorator method(s), do you really need to test for that? It seems like you are testing Object#extend in that case.
If you want to test the behavior of #model.foo, you don't need to do that in an integration test - that's the advantage of the decorator, you can then test it in isolation like
x = Object.new.extend(Decorator)
#.... assert something about x.foo ...
Mocking in integration tests is usually a code smell, in my experience.

why use include module when class_eval by itself would suffice

In the following code include module is used. The way I see it if include module is removed then also an instance method would be created. Then why user include module ?
http://github.com/rails/rails/blob/master/activerecord/lib/active_record/associations.rb#L1416
include Module.new {
class_eval <<-RUBY, __FILE__, __LINE__ + 1
def destroy # def destroy
super # super
#{reflection.name}.clear # posts.clear
end # end
RUBY
}
First of all let's make one thing clear. When they call super inside the class_eval — it has absolutely nothing to do with why they used include Module.new {} thing. In fact the super which was called inside the destroy method is completely irrelevant to answering your question. There could be any arbitrary code inside that destroy method.
Now that we got it out of the way, here's what's going on.
In ruby, if you simply define a class method, and then define it again in the same class, you will not be able to call super to access the previous method.
For example:
class Foo
def foo
'foo'
end
def foo
super + 'bar'
end
end
Foo.new.foo # => NoMethodError: super: no superclass method `foo' for #<Foo:0x101358098>
This makes sense, because the first foo was not defined in some superclass, or anywhere up the lookup chain (which is where super points). However, you can define the first foo in such a way that when you later overwrite it — it will be available by calling super. This is exactly what they wanted to achieve with doing module include.
class Foo
include Module.new { class_eval "def foo; 'foo' end" }
def foo
super + 'bar'
end
end
Foo.new.foo # => "foobar"
This works, because when you include a module, ruby inserts it into the lookup chain. This way you can subsequently call super in the second method, and expect the included method to be called. Great.
However, you may wonder, why not simply include a module without all the tricks? Why are they using block syntax? We know that my above example is exactly equivalent to the following:
module A
def foo
'foo'
end
end
class Foo
include A
def foo
super + 'bar'
end
end
Foo.new.foo # => "foobar"
So why didn't they do that? The answer is — the call to reflection. They needed to capture the variable (or method) which was available in the current context, which is reflection.
Since they are defining the new module using block syntax, all the variables outside of the block are available for usage inside the block. Convenient.
Just to illustrate.
class Foo
def self.add_foo_to_lookup_chain_which_returns(something)
# notice how I can use variable something in the class_eval string
include Module.new { class_eval "def foo; '#{something}' end" }
end
end
# so somewhere else I can do
class Foo
add_foo_to_lookup_chain_which_returns("hello")
def foo
super + " world"
end
end
Foo.new.foo # => "hello world"
Neat, huh?
Now let me stress it again. The call to super inside of the destroy method in your example has nothing to do with any of the above. They called it for their own reasons, because maybe the class where this is happening is subclassing another class which already defined destroy.
I hope this made it clear.
I'm guessing but... they don't want to overwrite the "destroy" method, and want to leave it available to be overloaded by some end-user (you or me), without it removing this "reflection.clear" functionality.
So - by including it as a module, they can call "super" which will call the original destroy or the overloaded version (written by the end-user).
Thanks to include, destroy method is not overwritten. It lands in ghost class that actual class derives from. That way, when one will call destroy on AR object, original one will be called, and super will call one from anonymous module (which will later call original destroy from class that it derived from).
A bit tricky, indeed.

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