如何在Ruby中删除整个数组并使用RSpec进行测试

Question

I'm fairly new to Ruby and am currently taking a full stack course. For one of my projects we are building an addressbook. I have set up how to add an entry to the addressbook, however, I can't seem to figure out how to delete an entry (I make an attempt with the remove_entry method in the AddressBook class below but am not having any luck). We are also supposed to test first with RSpec, have the test fail and then write some code to get it to pass. If I didn't include all the info needed for this question let me know (rookie here). Anyway, here is what I have so far:

RSpec

context ".remove_entry" do
    it "removes only one entry from the address book" do
      book = AddressBook.new
      entry = book.add_entry('Ada Lovelace', '010.012.1815', 'augusta.king@lovelace.com')
      book.remove_entry(entry)

      expect(entry).to eq nil
    end
  end

AddressBook class

require_relative "entry.rb"

class AddressBook
  attr_accessor :entries

  def initialize
    @entries = []
  end

  def add_entry(name, phone, email)
    index = 0
    @entries.each do |entry|
      if name < entry.name
        break
      end
      index += 1
    end

    @entries.insert(index, Entry.new(name, phone, email))
  end

  def remove_entry(entry)
    @entries.delete(entry)
  end
end

Entry class

class Entry
  attr_accessor :name, :phone_number, :email

  def initialize(name, phone_number, email)
    @name = name
    @phone_number = phone_number
    @email = email
  end

  def to_s
    "Name: #{@name}\nPhone Number: #{@phone_number}\nEmail: #{@email}"
  end
end

When testing my code with RSpec I receive the following error message:

.....F

Failures:

  1) AddressBook.remove_entry removes only one entry from the address book
     Failure/Error: expect(entry).to eq nil

       expected: nil
            got: [#<Entry:0x00000101bc82f0 @name="Ada Lovelace", @phone_number="010.012.1815", @email="augusta.king@lovelace.com">]

       (compared using ==)
     # ./spec/address_book_spec.rb:49:in `block (3 levels) in <top (required)>'

Finished in 0.02075 seconds (files took 0.14221 seconds to load)
6 examples, 1 failure

Failed examples:

rspec ./spec/address_book_spec.rb:44 # AddressBook.remove_entry removes only one entry from the address book

Answer 1

I think your expect has an issue. The entry variable is not set to nil , but the entry inside book would be nil .

I think something like this would work better:

expect(book.entries.find { |e| e.name == "Ada Lovelace" }).to eq nil

Better still, your AddressBook could have its own find method, which would make the expect param much nicer, like book.find(:name => "Ada Lovelace") .

Finally, I would also put an expect call before the remove_entry call, to make sure its result equals entry .

Answer 2

Just test that the book.entries association is empty:

expect(book.entries).to be_empty

As book is a local variable in your test, you will not get a false negative result if you keep your test atomic. Some best practices on rspec.

Edit : You can also check the entry was not in the set:

expect(book.entries.index(entry)).to be_nil

or test the change of the array length with:

expect { book.remove_entry(entry) }.to change{book.entries.count}.by(-1)

If you wonder for the be_xxx syntax sugar, if the object respond to xxx? , then you can use be_xxx in your tests ( predicate matchers )