w2d5

Question 1

What is a DSL?

Answer 1

A domain-specific language; used for a specific problem domain.

Question 2

What is the logic behind RSpec not testing private classes?

Answer 2

Private methods should support the public interface, so testing public methods should suffice.

Question 3

What is the directory structure for projects with RSpec?

Answer 3

my_cool_project
  lib/
    hello.rb
  spec/
    hello_spec.rb

Question 4

What requires must spec files have?

Answer 4

They must require ‘rspec’ and the name of the file they are testing.

Question 5

What is the ‘context’ keyword?

Answer 5

An alias for ‘describe’

Question 6

What is the difference between ‘describe’ and ‘it’?

Answer 6

Both take strings as arguments, but describe takes the name of a method and it takes a description of the behavior being tested in the ‘it’ block

Question 7

What are uses of the expect method?

Answer 7

expect(test_value).to eq(‘5’)

expect(test_value).to_not raise_error(ArgumentError)

Question 8

How can we create a shared group of tests?

Answer 8

RSpec.shared_examples “collections” do |collection_class|

Question 9

How can we use the ‘before’ method?

Answer 9

Use it to set up a context for testing:

before(:each) do
        board.make_move([3, 4], [2, 3])
        board.make_move([1, 2], [4, 5])
        board.make_move([5, 3], [5, 1])
        board.make_move([6, 3], [2, 4])
      end

Question 10

T/F: Ruby supports ‘!=’

Answer 10

F

Question 11

How can we define a subject for our tests?

Answer 11

subject(:robot) { Robot.new }

The symbol can then be accessed as an object:

‘robot.position’

Question 12

What is the proper TDD workflow

Answer 12

Red, Green, Refactor

Question 13

Where must the subject of an it block be declared?

Answer 13

Outside the it block.

Question 14

Say we have a function ‘fibs_rec’, which takes an argument ‘num’, dictating the number of fibonaccis to return. How can we right rspec stating that ‘fibs_rec’ should return the first 2 fibonacci numbers?

Answer 14

it “returns first two fib numbers” do
expect(fibs_rec(2)).to eq([0, 1])
end

Question 15

Let’s say ‘fibs_rec’ is a recursive function, and we expect it to call itself at least twice. What is the rspec to test this?

Answer 15

it “calls itself recursively” do
expect(self).to receive(:fibs_rec).at_least(:twice).and_call_original
fibs_rec(6)
end

Question 16

What goes inside a describe ‘string’ do end block?

Answer 16

Various it blocks.

Question 17

How can we create a variable ‘array’ with a value, and where should it be declared?

Answer 17

let(:array) { [1, 2, 3, 4, 5].shuffle }

It should be inside a do block but before the if blocks that reference it.

Question 18

How can we create a larger variable to use in rspec, like a large array?

Answer 18

use let (:object_name) do end

let(:dictionary) do
# a small dictionary of words
[“a”, “am”, “an”, “pa”, “pan”, “panama”]
end

Question 19

What is the difference between ‘let’ and ‘subject’

Answer 19

Subject can only be used once and is the main object for the tests in a describe block, whereas let is used for helper objects and can be used many times, although each time with a different scope for each it block.

Question 20

What is “memoization”?

Answer 20

Memoization means that the first time the method is invoked, the return value is cached and that same value is returned every subsequent time the method is invoked within the same scope.

Question 21

Does YAGNI apply when writing RSpec?

Answer 21

Absolutely; focus on getting down fundamental functionality first.

Question 22

How can we create a double with stub methods?

Answer 22

let(:customer) { double(“customer”, :email_address => “ned@appacademy.io”) }

Question 23

What is going on here, and how are method expectations set:

describe Order
let(:customer) { double(‘customer’) }
let(:product) { double(‘product’, :cost => 5.99) }
subject(:order) { Order.new(customer, product) }

it “subtracts item cost from customer account” do
expect(customer).to receive(:debit_account).with(5.99)
order.charge_customer
end
end

Answer 23

Here we want to test that when we call charge_customer on an Order object, it tells the customer to subtract the item price from the customer’s account. We also specify that we should check that we have passed #debit_account the correct price of the product.

Notice that we set the message expectation before we actually kick off the #charge_customer method. Expectations need to be set up in advance.

Question 24

What is distinct about integration tests?

Answer 24

Integration tests uses real objects instead of mocks in order to see if objects interact with one another correctly.