RSpec double/stubs

Question 1

How to stub value and return something?

Answer 1

before do
    # it calls stub 
    allow(animal).to receive(:name).and_return('hello') 
  end

it { expect(animal.name).to eq ‘hello’ }

Question 2

How to mock values with expectations?

Answer 2

# it calls mock
expect(animal).to receive(:name).and_return('hello')

Question 3

How to create spy?

Answer 3

allow(thing).to receive(:name).and_return("Fred")
# body of test
expect(thing).to have_received(:name)

Question 4

What are the full doubles?

Answer 4

Full double - entire objects that exist only to be

stubs

Question 5

What is partial doubles?

Answer 5

Partial doubles - can stub specific methods of existing

objects.

Question 6

How to create a full double?

Answer 6

let(:animal) { double(‘Optional name’, name: ‘hello’, age: 10) }

it { expect(animal.name).to eq ‘hello’ }

Question 7

How to return double itself if double does implement this method? ( 2 methods)

Answer 7

1) spy(‘Name’)

2) double(‘Optional name’).as_null_object

Question 8

What double types do you know? And what is the difference between them?

Answer 8

# allows any argument double('Project', name2: 'dd' )
1) double 
# allows to send only existing instance methods instance_double('Project', name: 'dd' )
2) instance_double 
# allows to send only existing class methods instance_double('Project', name: 'dd' )
3) class_double
# take an instance of obejct as the first argument object_double(Project.new, name: 'dd' )
4) object_double

Question 9

How to stub any instance of an object?

Answer 9

allow_any_instance_of(Project).to receive(:name).and_return(false)

Question 10

How to stub exception raising?

Answer 10

allow(animal).to receive(:name).and_raise(‘Error’)

Question 11

How to check that we run an object method twice?

Answer 11

expect(proj).to receive(:name).twice

Question 12

How to check that the object method doesn’t invoke?

Answer 12

expect(proj).not_to receive(:name)

Question 13

How to stub method with argument?

Answer 13

allow(animal).to receive(:name).with(1)

Question 14

How to stub method and call original?

Answer 14

allow(animal).to receive(:name).and_call_original

Question 15

How to check that we invoke something with a hash?

Answer 15

expect(animal).to receive(:name).with(a_hash_including(name: ‘Sample’))

Question 16

How to check that we invoke something with the specific argument type?

Answer 16

expect(animal).to receive(:name).with(a_kind_of(OpenStruct))

Question 17

How to check that we call some method twice in the cycle?

Answer 17

use and

expect { subject }.to publish(‘something’).with(
company: company1, employee_ids: employee_ids1).and publish(‘something’).with(
company: company2, employee_ids: employee_ids2
)

Question 18

What main stub/mock abstraction do you know? And what does they mean?

Answer 18

• Doubles (which act as fake collaborators in tests)
  double(upvotes: 0, downvotes: 5)
• Stubbing ( Sometimes however, we have to
  deal with collaborators that are hard-coded inside our object. We can isolate these objects too with a technique called stubbing.)
  allow(Link).to receive(:new).and_return(invalid_link)
• Mocking (When mocking an interaction with a collaborator we set up an expectation that it will receive a given message and then exercise the system to see if that does indeed happen.)
  expect(LinkMailer).to receive(:new_link).with(valid_link)
• Spying (Mocking can be a little weird because the expectation happens in the middle of the test. Spy checks expectation after the test was run)
  expect(LinkMailer).to have_received(:new_link).with(link)