I am having trouble testing methods similar to this using minitest where objects have references to other objects:
def drive num
old_place = #current_place.name
if num == 0
road = #current_place.first_place_road
#current_place = #current_place.first_place
else
road = #current_place.second_place_road
#current_place = #current_place.second_place
end
print_drive(old_place, road)
end
I am trying to test by creating 2 mock objects, and stubbing their methods to return the other mock.
def test_drive_to_first_place
start_place = Minitest::Mock.new
end_place = Minitest::Mock.new
def start_place.name; "first place"; end
def start_place.first_place; end_place; end
def start_place.first_place_road; "road"; end
def end_place.name; "end place"; end
def end_place.first_place; nil; end
def start_place.first_place_road; nil; end
driver = Driver::new "driver", start_place
driver.drive(0)
assert_output(stdout = ......
end
I am getting this error and Im not sure how to approach it. The objects im testing do not have any property or method :end_place, it is just used as a name in testing.
1) Error:
DriverTest#test_drive_to_first_place:
NoMethodError: unmocked method :end_place, expected one of []
The correct format to set a required response would be ...
start_place.expect(:first_place, end_place)
If you define a method, you don't have access to variables defined outside the method, so your def start_place.first_place... code can't work.
Related
I need to create a class where if the attribute value is the same it does not generate a new object id, example:
result:
described_class.new('01201201202')
<PixKey:0x00007eff5eab1ff8 #key="01201201202">
if i run it again with the same value it should keep the same object id
0x00007eff5eab1ff8
is similar behavior with the symbol
test:
describe '#==' do
let(:cpf) { described_class.new('01201201202') }
it 'verifies the key equality' do
expect(cpf).to eq described_class.new('01201201202')
end
end
Running the test shows an error, because the obejct id changes:
expected: #<PixKey:0x00007eff5eab1ff8 #key="01201201202">
got: #<PixKey:0x00007eff5eab2070 #key="01201201202">
Class:
class PixKey
def init(key)
#key = key
end
end
The other answers are fine, but they are a little more verbose than needed and they use class variables, which I find to be a confusing concept because of how they are shared among various classes.
class PixKey
#instances = {}
def self.new(id)
#instances[id] ||= super(id)
end
def initialize(id)
#key = id
end
end
p PixKey.new(1)
p PixKey.new(2)
p PixKey.new(2)
p PixKey.new(1)
Running the test shows an error, because the object id changes
Not quite. It shows an error because the objects are not equal. And the error message prints both objects including their id. But the object id is not what's causing the test to fail.
I need to create a class where if the attribute value is the same it does not generate a new object id
That would probably work, but you're likely approaching the problem from the wrong side. In Ruby, equality doesn't mean object identity. Two objects can be equal without being the same object, e.g.
a = 'foo'
b = 'foo'
a.object_id == b.object_id
#=> false
a == b
#=> true
There's no need to tinker with object ids to get your test passing. You just have to implement a custom == method, e.g.:
class PixKey
attr_reader :key
def initialize(key) # <- not "init"
#key = key
end
def ==(other)
self.class == other.class && self.key == other.key
end
end
The == method checks if both objects have the same class (i.e. if both are PixKey instances) and if their key's are equal.
This gives:
a = PixKey.new('01201201202')
b = PixKey.new('01201201202')
a == b
#=> true
Create a class method to create instances and have it look up a hash.
class PixKey
##instances = {}
def PixKey.create(id)
if not ##instances.has_key?(id)
##instances[id] = PixKey.new(id)
end
return ##instances[id]
end
def initialize(id)
#key = id
end
end
a = PixKey.new(123)
b = PixKey.new(123)
c = PixKey.create(123)
d = PixKey.create(123)
puts a
puts b
puts c
puts d
Output:
#<PixKey:0x000000010bc39900>
#<PixKey:0x000000010bc38078>
#<PixKey:0x000000010bc33eb0>
#<PixKey:0x000000010bc33eb0>
Notice the last two instances created with the PixKey.create(id) method return the same instance.
Note that Ruby's new method is just a method on Class and can be overridden like any other. The docs describe the default implementation.
Calls allocate to create a new object of class's class, then invokes that object's initialize method, passing it args. This is the method that ends up getting called whenever an object is constructed using .new.
So, if you want to keep the .new syntax and still get the same objects back, we can override new on the class and call super. This is exactly what OscarRyz' answer does, just with .new and super rather than a separate helper function.
class PixKey
##instances = {}
def PixKey.new(id)
if not ##instances.has_key?(id)
##instances[id] = super(id)
end
return ##instances[id]
end
def initialize(id)
#key = id
end
end
a = PixKey.new(123)
b = PixKey.new(123)
puts a
puts b
I have a class that defines a 'verify' method which is unfortunately the same name that MiniTest::Mock uses to verify a method has been called. I'm running into a clobbering problem.
I have classes defined as below.
class Reader
def initialize(verifier)
#verifier = verifier
end
def verify(subject)
#verifier.verify(subject)
end
end
class Verifier
def verify(subject)
subject != nil
end
end
I have tests setup as follows.
class TestReader < MiniTest::Test
def test_reader_when_verification_fails
mock_verifier = MiniTest::Mock.new
mock_verifier.expect :verify, false
reader = Reader.new(mock_verifier)
reader.verify(nil)
# The following verify method ends up being the 'verify' defined on
# Verifier, not on MiniTest::Mock. It blows up because Verifier#verify
# expects an argument.
mock_verifier.verify
end
end
How do I get around this?
EDIT: Original post (at bottom) was incorrect.
A working solution is:
#mock_verifier.instance_eval {
def assert
#expected_calls.each do |name, expected|
actual = #actual_calls.fetch(name, nil)
raise MockExpectationError, "expected #{__call name, expected[0]}" unless actual
raise MockExpectationError, "expected #{__call name, expected[actual.size]}, got [#{__call name, actual}]" if
actual.size < expected.size
end
true
end
}
* Below is incorrect *
Open up the mock, save off the MiniTest::Mock#verify method under a different method name (The -> Proc is needed to capture scope), then un-define 'verify' on the mock.
def #mock_verifier.assert
-> { #mock_verifier.method(:verify) }
end
#mock_verifier.instance_eval 'undef :verify'
Now at the end you do
#mock_verifier.expect :verify, false
#reader.verify(nil)
#mock_verifier.assert
I have an issue I have been whacking my head against for hours now, and neither I nor anyone I have asked has been able to come up with a suitable answer.
Essentially, I am writing a method that allows me to edit an instance variable of another method. I have multiple ways of doing this, however my issue is with writing the test for this method. I have tried many different double types, however as they are immutable and do not store states, I did not manage to find a way to make it work.
Here is the class whose working variable is changed:
class MyClass
attr_writer :working
def working?
#working
end
end
Here is the class and method that change it:
class OtherClass
def makes_work
#ary_of_instances_of_MyClass_to_fix.map do |x|
x.working = true
#ary_of_fixed_objects << x
end
end
end
(The actual class is much larger, but I have only included a generalised version of the method in question. I can put all of the specific code up in a gist if it would help)
So I need a way to test that makes_work does in fact accept the array of objects to be changed, changes them and appends them to array_of_fixed_objects. What would be the best way of testing this in a containerised way, without requiring MyClass?
My last attempt was using spies to see what methods were called on my dummy instance, however a range of failures, depending on what I did. Here is the most recent test I wrote:
describe '#make_work' do
it 'returns array of working instances' do
test_obj = spy('test_obj')
subject.ary_of_instances_of_MyClass_to_fix = [test_obj]
subject.makes_work
expect(test_obj).to have_received(working = true)
end
end
This currently throws the error:
undefined method to_sym for true:TrueClass
Many thanks for any help! I apologise if some formatting/ info is a little bit messed up, I am still pretty new to this whole stackoverflow thing!
I think the problem is have_received(working = true), it should be have_received(:working=).with(true)
Edit:
Examples of using have_received
https://github.com/rspec/rspec-mocks#test-spies
https://relishapp.com/rspec/rspec-mocks/v/3-5/docs/setting-constraints/matching-arguments
This works for me
class MyClass
attr_writer :working
def working?
#working
end
end
class OtherClass
attr_writer :ary_of_instances_of_MyClass_to_fix
def initialize
#ary_of_fixed_objects = []
end
def makes_work
#ary_of_instances_of_MyClass_to_fix.map do |x|
x.working = true
#ary_of_fixed_objects << x
end
end
end
describe '#make_work' do
subject { OtherClass.new }
it 'returns array of working instances' do
test_obj = spy('test_obj')
subject.ary_of_instances_of_MyClass_to_fix = [test_obj]
subject.makes_work
expect(test_obj).to have_received(:working=).with(true)
end
end
If you'd rather just avoid stubbing, you could use an instance of OpenStruct instead of a double:
class OtherClass
attr_writer :ary_of_instances_of_MyClass_to_fix
def initialize
#ary_of_instances_of_MyClass_to_fix, #ary_of_fixed_objects = [], []
end
def makes_work
#ary_of_instances_of_MyClass_to_fix.map do |x|
x.working = true
#ary_of_fixed_objects << x
end
#ary_of_fixed_objects
end
end
require 'ostruct'
RSpec.describe "#makes_work" do
describe "given an array" do
let(:array) { [OpenStruct.new(working: nil)] }
subject { OtherClass.new }
before do
subject.ary_of_instances_of_MyClass_to_fix = array
end
it "sets the 'working' attribute for each element" do
expect(array.map(&:working)).to eq [nil]
subject.makes_work
expect(array.map(&:working)).to eq [true]
end
end
end
I have a Team class in my program and I am trying to use method_missing
but instead of running the function when the method doesn't exist, it gives me an error:"undefined method `hawks' for Team:Class (NoMethodError)"
My code is as follows:
class Team
attr_accessor :cust_roster, :cust_total_per, :cust_name, :cust_best_player
##teams = []
def initialize(stats = {})
#cust_roster = stats.fetch(:roster) || []
#cust_total_per = stats.fetch(:per)
#cust_name = stats.fetch(:name)
#cust_best_player = stats.fetch(:best)
##teams << self
end
def method_missing(methId)
str = methID.id2name
Team.new(roster:[], per: 0, name: str.uppercase, best: 0)
end
class <<self
def all_teams
##teams
end
end
end
hawks = Team.hawks
There are a number of problems with your code. Let's go through one by one.
From the documentation,
method_missing(*args) private
Invoked by Ruby when obj is sent a message it cannot handle.
Here message refers to the method. In ruby, whenever you're calling a method on an object, you're actually sending a message to the object
To better understand this, try this in the irb shell.
1+2
=> 3
1.send(:+,2)
=> 3
Here 1 and 2 are objects of Fixnum class. You can confirm that by using 1.class. Ok, back to your question. So, a method_missing method should be called on an instance.
team = Team.new
team.hawks
If you try the above piece of code, you'll get an error saying 'fetch': key not found: :roster (KeyError)
You can get around this by passing a default value as the second parameter to fetch method. Replace your initialize method with
def initialize(stats = {})
#cust_roster = stats.fetch(:roster, [])
#cust_total_per = stats.fetch(:per, 0)
#cust_name = stats.fetch(:name, "anon")
#cust_best_player = stats.fetch(:best, "anon")
##teams << self
end
If you execute the script, you'll get a stack level too deep (SystemStackError) because of a small typo in this line.
str = methID.id2name
In the method definition, you're receiving an argument with the name of methId but inside you're trying to call methID. Fix it with
str = methId.id2name
If you execute your script, you'll again get an error saying undefined method uppercase for "hawks":String (NoMethodError)
This is because there is no uppercase method on strings. You should instead use the upcase method.
Team.new(roster:[], per: 0, name: str.upcase, best: 0)
and you should be good to go.
For more, see http://apidock.com/ruby/BasicObject/method_missing
Hope this helps!
class Team
attr_accessor :cust_roster, :cust_total_per, :cust_name, :cust_best_player
##teams = []
def initialize(stats = {roster: [], per: 0, name: "", best: 0}) # I added the default values here.
#cust_roster = stats.fetch(:roster)
#cust_total_per = stats.fetch(:per)
#cust_name = stats.fetch(:name)
#cust_best_player = stats.fetch(:best)
##teams << self
end
def method_missing(name, *args)
self.cust_name = name.to_s.upcase
end
class << self
def all_teams
##teams
end
end
end
team_hawks = Team.new #=> create an instance of Team class, I renamed the object to avoid confusions.
team_hawks.hawks #=> called method_missing which assigned the cust_name variable to "HAWKS"
team_hawks.cust_name #=> HAWKS, so cust_name is assigned to be hawks. This is to check if the assignment worked.
Hope this is what you are looking for.
Let's say I have a class Foo and the constructor takes 2 parameters.
Based on these parameters the initialize method does some heavy calculations and stores them as variables in the instance of the class. Object created.
Now I want to optimize this and create a cache of these objects. When creating a new Foo object, I want to return a existing one from the cache if the parameters match. How can I do this?
I currently have a self.new_using_cache(param1, param2), but I would love to have this integrated in the normal Foo.new().
Is this possible in any way?
I can also deduct that using .new() combined with a cache is not really syntactical correct.
That would mean that the method should be called new_or_from_cache().
clarification
It's not just about the heavy calculation, it's also preferred because of limiting the amount of duplicate objects. I don't want 5000 objects in memory, when I can have 50 unique ones from a cache. So I really need to customize the .new method, not just the cached values.
class Foo
##cache = {}
def self.new(value)
if ##cache[value]
##cache[value]
else
##cache[value] = super(value)
end
end
def initialize(value)
#value = value
end
end
puts Foo.new(1).object_id #2148123860
puts Foo.new(2).object_id #2148123820 (different from first instance)
puts Foo.new(1).object_id #2148123860 (same as first instance)
You can actually define self.new, then call super if you actually want to use Class#new.
Also, this totally approach prevents any instantiation from ever occurring if a new instance isn't actually needed. This is die to the fact the initialize method doesn't actually make the decision.
Here's a solution I came up with by defining a generic caching module. The module expects your class to implement the "retrieve_from_cache" and "store_in_cache" methods. If those methods don't exist, it doesn't attempt to do any fancy caching.
module CacheInitializer
def new(*args)
if respond_to?(:retrieve_from_cache) &&
cache_hit = retrieve_from_cache(*args)
cache_hit
else
object = super
store_in_cache(object, *args) if respond_to?(:store_in_cache)
object
end
end
end
class MyObject
attr_accessor :foo, :bar
extend CacheInitializer
#cache = {}
def initialize(foo, bar)
#foo = foo
#bar = bar
end
def self.retrieve_from_cache(foo, bar)
# grab the object from the cache
#cache[cache_key(foo, bar)]
end
def self.store_in_cache(object, foo, bar)
# write back to cache
#cache[cache_key(foo, bar)] = object
end
private
def self.cache_key(foo, bar)
foo + bar
end
end
Something like this?
class Foo
##cache = {}
def initialize prm1, prm2
if ##cache.key?([prm1, prm2]) then #prm1, #prm2 = ##cache[[prm1, prm2]] else
#prm1 = ...
#prm2 = ...
##cache[[prm1, prm2]] = [#prm1, #prm2]
end
end
end
Edited
To not create an instance when the parameters are the same as before,
class Foo
##cache = {}
def self.new prm1, prm2
return if ##cache.key?([prm1, prm2])
#prm1 = ...
#prm2 = ...
##cache[[prm1, prm2]] = [#prm1, #prm2]
super
end
end
p Foo.new(1, 2)
p Foo.new(3, 4)
p Foo.new(1, 2)
# => #<Foo:0x897c4f0>
# => #<Foo:0x897c478>
# => nil
You could use a class-level instance variable to store results from previous object instantiations:
class Foo
#object_cache = {}
def initialize(param1, param2)
#foo1 = #object_cache[param1] || #object_cache[param1] = expensive_calculation
#foo2 = #object_cache[param2] || #object_cache[param2] = expensive_calculation
end
private
def expensive_calculation
...
enf
end
As you probably know you have reinvented the factory method design pattern and it's a perfectly valid solution using your name for the factory method. In fact, it's probably better to do it without redefining new if anyone else is going to have to understand it.
But, it can be done. Here is my take:
class Test
##cache = {}
class << self
alias_method :real_new, :new
end
def self.new p1
o = ##cache[p1]
if o
s = "returning cached object"
else
##cache[p1] = o = real_new(p1)
s = "created new object"
end
puts "%s (%d: %x)" % [s, p1, o.object_id]
o
end
def initialize p
puts "(initialize #{p})"
end
end
Test.new 1
Test.new 2
Test.new 1
Test.new 2
Test.new 3
And this results in:
(initialize 1)
created new object (1: 81176de0)
(initialize 2)
created new object (2: 81176d54)
returning cached object (1: 81176de0)
returning cached object (2: 81176d54)
(initialize 3)