rspec.md

   1 ---
   2 title: RSpec
   3 category: Ruby
   4 layout: 2017/sheet
   5 ---
   6
   7 ### About
   8 {: .-intro}
   9
  10 RSpec is a Ruby library for testing.
  11
  12 - <https://rspec.info/>
  13
  14 ### Invoking tests
  15
  16 ```sh
  17 rake -T spec      # List spec tasks
  18
  19 rake spec         # Run all
  20
  21 rake spec/models/mymodel_spec.rb
  22 rake spec/models/mymodel_spec.rb:27
  23 ```
  24
  25 ## Writing tests
  26
  27 ```rb
  28 describe "A User (in general)" do
  29   include UserSpecHelper
  30
  31   subject { Person.new }
  32
  33   let(:admin) { Person.new(role: :admin) }
  34
  35   context "setter methods" do
  36     it "should do this" do
  37       pending "some other thing"
  38
  39       expect(subject.name).to eq 'x'
  40     end
  41   end
  42 end
  43 ```
  44
  45 ### Before/after
  46
  47 ```rb
  48 before :each do
  49   # before all tests
  50 end
  51
  52 before do
  53   # before this suite
  54 end
  55
  56 after do
  57   # after this suite
  58 end
  59 ```
  60
  61 ### Subjects
  62
  63 ```rb
  64 subject { CheckingAccount.new }
  65 it { is_expected.to be_empty }
  66
  67 # also names: subject(:account) { ... }
  68 ```
  69
  70 ## Expectations
  71
  72 ```rb
  73 target.should eq 1
  74 target.should_not eq 1
  75
  76 expect(target).to eq 1
  77 expect(target).not_to eq 1
  78 ```
  79
  80 ### Numeric
  81
  82 ```rb
  83 expect(5).to be < 6
  84 expect(5).to == 5
  85 expect(5).to equal value
  86 expect(5).to be_between(1, 10)
  87 expect(5).to be_within(0.05).of value
  88 ```
  89
  90 ### Compound expectations
  91
  92 ```rb
  93 expect(1).to (be < 2).or be > 5
  94 ```
  95
  96 Use `or`/`and` to string multiple matchers together. See: [Compound expectations](https://relishapp.com/rspec/rspec-expectations/docs/compound-expectations)
  97
  98 ### Comparison
  99
 100 ```rb
 101 expect(x).to be value
 102 expect(x).to satisfy { |arg| ... }
 103 expect(x).to match /regexp/
 104 ```
 105
 106 ### Predicate
 107
 108 ```rb
 109 expect(x).to be_zero    # FixNum#zero?
 110 expect(x).to be_empty   # Array#empty?
 111 expect(x).to have_key   # Hash#has_key?
 112 ```
 113
 114 ### Objects
 115
 116 ```rb
 117 expect(obj).to be_an_instance_of MyClass
 118 expect(obj).to be_a_kind_of MyClass
 119 expect(obj).to respond_to :save!
 120 ```
 121
 122 ### Control flow
 123
 124 ```rb
 125 expect { user.save! }.to raise_error
 126 expect { user.save! }.to raise_error(ExceptionName, /msg/)
 127 expect { user.save! }.to throw :symbol
 128 ```
 129
 130 ### Enumerables/arrays
 131
 132 ```rb
 133 expect(list).to include(<object>)
 134
 135 expect(list).to have(1).things
 136 expect(list).to have_at_least(2).things
 137 expect(list).to have_at_most(3).things
 138
 139 expect(list).to have(2).errors_on(:field)
 140 ```
 141
 142 ### Change
 143
 144 ```rb
 145 expect { thing.approve! }.to \
 146   change(thing, :status)
 147   .from(Status::AWAITING_APPROVAL)
 148   .to(Status::APPROVED)
 149
 150 expect { thing.destroy }.to \
 151   change(Thing, :count)
 152   .by(-1)
 153 ```
 154
 155 ## Doubles
 156
 157 ```rb
 158 book = double('book')
 159 book = instance_double('Book', pages: 250)
 160 ```
 161
 162 ### Method stubs
 163
 164 ```rb
 165 allow(die).to receive(:roll)
 166 allow(die).to receive(:roll) { 3 }
 167 allow_any_instance_of(Die).to receive(:roll)
 168
 169 expect(die).to receive(:roll)
 170   .with(1)
 171   .with(1, true)
 172   .with(boolean)
 173   .with(anything)
 174   .with(any_args)
 175   .with(1, any_args)
 176   .with(no_args)
 177   .with(hash_including(a: 1))
 178   .with(hash_excluding(a: 1))
 179   .with(array_including(:a, :b))
 180   .with(array_excluding(:a, :b))
 181   .with(instance_of(Fixnum))
 182   .with(kind_of(Numeric))
 183   .with(<matcher>)
 184
 185   .once
 186   .twice
 187   .exactly(n).times
 188   .at_least(:once)
 189   .at_least(:twice)
 190   .at_least(n).times
 191   .at_most(:once)
 192   .at_most(:twice)
 193   .at_most(n).times
 194 ```
 195
 196 https://relishapp.com/rspec/rspec-mocks/docs
 197
 198 ## Spec helpers
 199
 200 ```rb
 201 module UserSpecHelper
 202   def valid_user_attributes
 203     { :email => "joe@bloggs.com",
 204       :username => "joebloggs",
 205       :password => "abcdefg"}
 206   end
 207 end
 208 ```
 209
 210 ```rb
 211 describe User do
 212   include UserSpecHelper
 213
 214   ...
 215 end
 216 ```