Testing 201, or: Great Expectations

Transcript

1. TESTING 201
   OR: GREAT EXPECTATIONS
   JOE MASTEY, AUGUST 2020
   

   View Slide

2. LOTS OF RSPEC,
   FACTORY BOT,
   AND RAILS
   

   View Slide

3. EVERYONE IS
   DOING THEIR BEST
   

   View Slide

4. HEURISTICS,
   NOT RULES
   

   View Slide

5. PROLOGUE: THE TROUBLE
   WITH A SIMPLE TEST
   

   View Slide

6. class CreateShipmentHistoryReport
   attr_accessor :user, :shipments
   def initialize(user)
   @user = user
   @shipments = user.shipments
   end
   def process
   shipments.sort_by(&:created_at)
   data = shipments.map do |shipment|
   shipment.to_json.values +
   [ shipment.user.name,
   shipment.product.name ]
   end
   file = CSV.open(tmp_filename) do |csv|
   csv << shipments.first.to_json.keys + ['user', 'product']
   data.map do |row|
   csv << row
   end
   end
   persist_csv_to_s3(file)
   notify_user(user.email)
   file
   end
   end
   

   View Slide

7. class CreateShipmentHistoryReport
   attr_accessor :user, :shipments
   def initialize(user)
   @user = user
   @shipments = user.shipments
   end
   

   View Slide

8. def process
   shipments.sort_by(&:created_at)
   data = shipments.map do |shipment|
   shipment.to_json.values +
   [ shipment.user.name,
   shipment.product.name ]
   end
   # continued below...
   

   View Slide

9. # ... process continued
   file = CSV.open(tmp_filename) do |csv|
   csv << shipments.first.to_json.keys + ['user', 'product']
   data.map do |row|
   csv << row
   end
   end
   persist_csv_to_s3(file)
   notify_user(user.email)
   file
   end
   

   View Slide

10. class CreateShipmentHistoryReport
    attr_accessor :user, :shipments
    def initialize(user)
    @user = user
    @shipments = user.shipments
    end
    def process
    shipments.order('created_at desc')
    data = shipments.map do |shipment|
    shipment.to_json.values +
    [ shipment.user.name,
    shipment.product.name ]
    end
    file = CSV.open(tmp_filename) do |csv|
    csv << shipments.first.to_json.keys + ['user', 'product']
    data.map do |row|
    csv << row
    end
    end
    persist_csv_to_s3(file)
    notify_user(user.email)
    file
    end
    end
    

    View Slide

11. describe CreateShipmentHistoryReport do
    describe "#process" do
    # ...
    it "generates an array of strings" do
    expect(csv_data.length).to eq(shipments.length)
    expect(csv_data).to all(be_an(Array))
    end
    it "matches the expected output" do
    expect(csv_data).to eq(output_records)
    end
    end
    end
    

    View Slide

12. let(:subject) { described_class.new(user).process }
    let(:csv_data) { CSV.parse(subject) }
    

    View Slide

13. let(:user) { create(:user, :signup_complete) }
    let(:subscription) { create(:subscription) }
    before do
    user.subscriptions << subscription
    expect(user)
    .to receive(:shipments)
    .and_return(shipments)
    end
    

    View Slide

14. let(:shipments) do
    [
    shipment_1,
    shipment_2,
    shipment_3,
    shipment_4
    ]
    end
    

    View Slide

15. let!(:shipment_1) { create(:shipment, product: product_1,
    created_at: 2.days.ago) }
    let!(:shipment_2) { create(:shipment, product: product_2,
    created_at: 3.days.ago) }
    let!(:shipment_3) { create(:shipment, product: product_3,
    created_at: 4.days.ago) }
    let!(:shipment_4) { create(:shipment, product: product_4,
    created_at: 5.days.ago) }
    

    View Slide

16. let(:product_1) { create(:product) }
    let(:product_2) { create(:product) }
    let(:product_3) { create(:product) }
    let(:product_4) { create(:product) }
    

    View Slide

17. let(:output_records) do
    [
    [shipment_4.created_on, shipment_4.completed_on,
    user.name, product_4.name],
    [shipment_3.created_on, shipment_3.completed_on,
    user.name, product_3.name],
    [shipment_2.created_on, shipment_2.completed_on,
    user.name, product_2.name],
    [shipment_1.created_on, shipment_1.completed_on,
    user.name, product_1.name],
    ]
    end
    

    View Slide

18. before do
    expect_any_instance_of(described_class)
    .to receive(:save_to_s3)
    .and_return(true)
    expect_any_instance_of(described_class)
    .to receive(:email_user)
    .and_return(true)
    end
    

    View Slide

19. it "matches the expected output" do
    expect(csv_data).to eq(output_records)
    end
    

    View Slide

20. describe CreateShipmentHistoryReport do
    describe "#process" do
    let(:user) { create(:user, :signup_complete) }
    let(:subscription) { create(:subscription) }
    let(:product_1) { create(:product) }
    let(:product_2) { create(:product) }
    let(:product_3) { create(:product) }
    let(:product_4) { create(:product) }
    let!(:shipment_1) { create(:shipment, product: product_1,
    created_at: 2.days.ago) }
    let!(:shipment_2) { create(:shipment, product: product_2,
    created_at: 3.days.ago) }
    let!(:shipment_3) { create(:shipment, product: product_3,
    created_at: 4.days.ago) }
    let!(:shipment_4) { create(:shipment, product: product_4,
    created_at: 5.days.ago) }
    let(:subject) { described_class.new(user).process }
    let(:csv_data) { CSV.parse(subject) }
    let(:shipments) do
    [
    shipment_1,
    shipment_2,
    shipment_3,
    shipment_4
    ]
    end
    let(:output_records) do
    [
    [shipment_4.created_on, shipment_4.completed_on,
    user.name, product_4.name],
    [shipment_3.created_on, shipment_3.completed_on,
    user.name, product_3.name],
    [shipment_2.created_on, shipment_2.completed_on,
    user.name, product_2.name],
    [shipment_1.created_on, shipment_1.completed_on,
    user.name, product_1.name],
    ]
    end
    before do
    user.subscriptions << subscription
    expect(user)
    .to receive(:shipments)
    .and_return(shipments)
    expect_any_instance_of(described_class)
    .to receive(:save_to_s3)
    .and_return(true)
    expect_any_instance_of(described_class)
    .to receive(:email_user)
    .and_return(true)
    end
    it "generates an array of strings" do
    expect(csv_data.length).to eq(shipments.length)
    expect(csv_data).to all(be_an(Array))
    end
    it "matches the expected output" do
    expect(csv_data).to eq(output_records)
    end
    end
    end
    

    View Slide

21. FOCUSING ON THE
    WRONG THINGS
    

    View Slide

22. THE 3 ROLES
    OF TESTING (IN ORDER)
    

    View Slide

23. 1. DESIGN FEEDBACK
    2. DOCUMENTATION
    3. VERIFICATION
    

    View Slide

24. TESTS AS
    DESIGN FEEDBACK
    

    View Slide

25. A NOTE ON TDD
    

    View Slide

26. CODE THAT’S DIFFICULT TO
    TEST IS TRYING TO TELL YOU
    SOMETHING IMPORTANT
    

    View Slide

27. IT’S EASIER TO WORK WITH
    OBJECTS IN SMALL CHUNKS.
    

    View Slide

28. let(:csv_data) { CSV.parse(subject) }
    before do
    expect_any_instance_of(described_class)
    .to receive(:save_to_s3)
    .and_return(true)
    expect_any_instance_of(described_class)
    .to receive(:email_user)
    .and_return(true)
    end
    

    View Slide

29. def data(shipments: @shipments)
    shipments.sort_by!(&:created_at)
    shipments.map do |shipment|
    shipment.to_json.values +
    [ shipment.user.name,
    shipment.product.name ]
    end
    end
    def headers
    shipments.first.to_json.keys + ['user', 'product']
    end
    

    View Slide

30. file = CSV.open(tmp_filename) do |csv|
    csv << headers
    data(shipments).map { |row| csv << row }
    end
    

    View Slide

31. it "matches the expected output" do
    subject = described_class.new(user)
    expect(subject.data).to eq(output_records)
    end
    

    View Slide

32. before do
    # expect_any_instance_of(described_class)
    # .to receive(:save_to_s3)
    # .and_return(true)
    # expect_any_instance_of(described_class)
    # .to receive(:email_user)
    # .and_return(true)
    end
    

    View Slide

33. before do
    expect(user)
    .to receive(:shipments)
    .and_return(shipments)
    end
    

    View Slide

34. class CreateShipmentHistoryReport
    def initialize(user, shipments = user.shipments)
    @user = user
    @shipments = shipments
    end
    end
    

    View Slide

35. before do
    # expect(user)
    # .to receive(:shipments)
    # .and_return(shipments)
    end
    described_class.new(user, shipments)
    

    View Slide

36. it "matches the expected output" do
    subject = described_class.new(user, shipments)
    expect(subject.data).to eq(output_records)
    end
    

    View Slide

37. def data(shipments)
    shipments.sort_by!(&:created_at)
    shipments.map do |shipment|
    shipment.to_json.values +
    [ shipment.user.name,
    shipment.product.name ]
    end
    end
    def headers
    shipments.first.to_json.keys + ['user', 'product']
    end
    

    View Slide

38. def serialize(shipment)
    {
    created_on: shipment.created_on,
    completed_on: shipment.completed_on,
    user: shipment.user.name,
    product: shipment.product.name,
    }
    end
    

    View Slide

39. def data(shipments)
    shipments.sort_by!(&:created_at)
    shipments.map { |shipment| serialize(shipment) }
    end
    def headers
    serialize(shipments.first).keys
    end
    

    View Slide

40. describe "#serialize" do
    it "serializes some shipment and user data" do
    shipment = create(:shipment)
    report = described_class.new(user, [])
    result = report.serialize(shipment)
    expect(result).to eq({
    created_on: shipment.created_on,
    completed_on: shipment.completed_on,
    user: shipment.user.name,
    product: shipment.product.name,
    })
    end
    end
    

    View Slide

41. # let(:output_records) do
    # [
    # [shipment_4.created_on, shipment_4.completed_on,
    # user.name, product_4.name],
    # [shipment_3.created_on, shipment_3.completed_on,
    # user.name, product_3.name],
    # [shipment_2.created_on, shipment_2.completed_on,
    # user.name, product_2.name],
    # [shipment_1.created_on, shipment_1.completed_on,
    # user.name, product_1.name],
    # ]
    # end
    

    View Slide

42. describe "ordering" do
    it "reorders shipments by their creation date" do
    report = described_class.new(user,[shipment_1, shipment_2])
    result = report.data
    expect(result.map(&:first)).to eq(
    [shipment_2.created_on, shipment_1.created_on]
    )
    end
    end
    

    View Slide

43. CREATE AS FEW RECORDS
    AS YOU CAN (AND ONLY
    RELATED ONES)
    

    View Slide

44. let(:user) { create(:user, :signup_complete) }
    let(:subscription) { create(:subscription) }
    before do
    user.subscriptions << subscription
    end
    

    View Slide

45. Factory AR records AR queries
    create(:user) 1 10
    create(:meal) 5 41
    create(:full_menu) 94 584
    create(:weekly_basket) 104 644
    create(:user, :with_order_history) 379 2336
    

    View Slide

46. let(:user) do
    instance_double(User, email: "[email protected]", shipments: shipments)
    end
    

    View Slide

47. let(:user) { User.new(email: "[email protected]", name: "Joe") }
    

    View Slide

48. describe "ordering" do
    it "reorders shipments by their creation date" do
    report = described_class.new(user, [shipment_1, shipment_2])
    result = report.data
    expect(result.map(&:first)).to eq(
    [shipment_2.created_on, shipment_1.created_on]
    )
    end
    end
    

    View Slide

49. PAY ATTENTION WHEN
    CLASSES DO TOO MUCH
    

    View Slide

50. def process
    def serialize(shipment)
    def data(shipments)
    def headers
    def save_to_s3(file)
    def notify_user(email)
    

    View Slide

51. TESTS AS
    DOCUMENTATION
    

    View Slide

52. OPTIMIZE TESTS FOR
    HUMAN UNDERSTANDING
    

    View Slide

53. it "matches the expected output" do
    expect(csv_data).to eq(output_records)
    end
    

    View Slide

54. describe "ordering" do
    it "reorders shipments by their creation date" do
    old = create_shipment(date: 9.days.ago)
    new = create_shipment(date: 2.days.ago)
    report = described_class.new(user, [new, old])
    result = report.data
    expect(result.map(&:first)).to eq(
    [old.created_on, new.created_on]
    )
    end
    end
    

    View Slide

55. it "serializes users as passed into the service" do
    users = create_list(:user, 3)
    response = subject.new(User.all).process
    response = response[0][4]
    expect(response).to eq(users.first.name)
    end
    

    View Slide

56. it "serializes users as passed into the service" do
    users = create_list(:user, 3)
    serialized_users = subject.new.serialize(users)
    response = serialized_users.first.full_name
    expect(response).to eq(users.first.name)
    end
    

    View Slide

57. PAY ATTENTION TO
    SIMILARITY AND DIFFERENCE
    

    View Slide

58. let(:product_1) { create(:product) }
    let(:product_2) { create(:product) }
    let(:product_3) { create(:product) }
    let(:product_4) { create(:product) }
    

    View Slide

59. let!(:shipment_1) { create(:shipment, product: product_1,
    created_at: 2.days.ago) }
    let!(:shipment_2) { create(:shipment, product: product_2,
    created_at: 3.days.ago) }
    let!(:shipment_3) { create(:shipment, product: product_3,
    created_at: 4.days.ago) }
    let!(:shipment_4) { create(:shipment, product: product_4,
    created_at: 5.days.ago) }
    

    View Slide

60. let(:output_records) do
    [
    [shipment_4.created_on, shipment_4.completed_on,
    user.name, product_4.name],
    [shipment_3.created_on, shipment_3.completed_on,
    user.name, product_3.name],
    [shipment_2.created_on, shipment_2.completed_on,
    user.name, product_2.name],
    [shipment_1.created_on, shipment_1.completed_on,
    user.name, product_1.name],
    ]
    end
    

    View Slide

61. def create_shipment(date:)
    product = create(:product)
    create(:shipment, product: product, created_at: date)
    end
    

    View Slide

62. describe "ordering" do
    it "reorders shipments by their creation date" do
    old = create_shipment(date: 9.days.ago)
    new = create_shipment(date: 2.days.ago)
    report = described_class.new(user, [new, old])
    result = report.data
    expect(result.map(&:first)).to eq(
    [old.created_on, new.created_on]
    )
    end
    end
    

    View Slide

63. # let(:product_1) { create(:product) }
    # let(:product_2) { create(:product) }
    # let(:product_3) { create(:product) }
    # let(:product_4) { create(:product) }
    # let!(:shipment_1) { create(:shipment,
    product: product_1,
    # created_at:
    2.days.ago) }
    # let!(:shipment_2) { create(:shipment,
    product: product_2,
    # created_at:
    3.days.ago) }
    # let!(:shipment_3) { create(:shipment,
    product: product_3,
    # created_at:
    4.days.ago) }
    # let!(:shipment_4) { create(:shipment,
    product: product_4,
    # created_at:
    5.days.ago) }
    #
    # let(:shipments) do
    # [
    # shipment_1,
    # shipment_2,
    # shipment_3,
    # shipment_4
    # ]
    # end
    # let(:output_records) do
    # [
    # [shipment_4.created_on,
    shipment_4.completed_on,
    # user.name, product_4.name],
    # [shipment_3.created_on,
    shipment_3.completed_on,
    # user.name, product_3.name],
    # [shipment_2.created_on,
    shipment_2.completed_on,
    # user.name, product_2.name],
    # [shipment_1.created_on,
    shipment_1.completed_on,
    # user.name, product_1.name],
    # ]
    # end
    

    View Slide

64. TRY TO STICK TO A GIVEN/
    WHEN/THEN STRUCTURE
    

    View Slide

65. describe "ordering" do
    it "reorders shipments by their creation date" do
    old = create_shipment(date: 9.days.ago)
    new = create_shipment(date: 2.days.ago)
    report = described_class.new(user, [new, old])
    result = report.data
    expect(result.map(&:first)).to eq(
    [old.created_on, new.created_on]
    )
    end
    end
    

    View Slide

66. describe "ordering" do
    it "reorders shipments by their creation date" do
    # Given
    old = create_shipment(date: 9.days.ago)
    new = create_shipment(date: 2.days.ago)
    # When
    report = described_class.new(user, [new, old])
    result = report.data
    # Then
    expect(result.map(&:first)).to eq(
    [old.created_on, new.created_on]
    )
    end
    end
    

    View Slide

67. it "reorders shipments by their creation date" do
    old = create_shipment(date: 9.days.ago)
    new = create_shipment(date: 2.days.ago)
    report = described_class.new(user, [new, old])
    expect(report.data.map(&:first)).to eq([old, new])
    end
    

    View Slide

68. before do
    expect_any_instance_of(described_class)
    .to receive(:save_to_s3)
    .and_return(true)
    expect_any_instance_of(described_class)
    .to receive(:email_user)
    .and_return(true)
    end
    

    View Slide

69. USING G/W/T EMPHASIZES
    SAMENESS AND
    DIFFERENCE.
    

    View Slide

70. it "returns order units summed, divided by units per shipper" do
    create_store_order(count_units: 4)
    create_store_order(count_units: 8)
    subject = described_class.new(store_orders: store_orders)
    total_shippers = subject.total_shipper_count
    expect(total_shippers).to eq(3)
    end
    

    View Slide

71. it "returns a ceiling rounded value" do
    create_store_order(count_units: 7)
    subject = described_class.new(store_orders: store_orders)
    total_shippers = subject.total_shipper_count
    expect(total_shippers).to eq(2)
    end
    

    View Slide

72. let!(:shipment_1) { create(:shipment, product: product_1,
    created_at: 2.days.ago) }
    let!(:shipment_2) { create(:shipment, product: product_2,
    created_at: 3.days.ago) }
    let!(:shipment_3) { create(:shipment, product: product_3,
    created_at: 4.days.ago) }
    let!(:shipment_4) { create(:shipment, product: product_4,
    created_at: 5.days.ago) }
    

    View Slide

73. TESTS DON’T NEED TO BE
    (TOO) DRY
    

    View Slide

74. it "returns order units summed, divided by units per shipper" do
    create_store_order(count_units: 4)
    create_store_order(count_units: 8)
    subject = described_class.new(store_orders: store_orders)
    total_shippers = subject.total_shipper_count
    expect(total_shippers).to eq(3)
    end
    it "returns a ceiling rounded value" do
    create_store_order(count_units: 7)
    subject = described_class.new(store_orders: store_orders)
    total_shippers = subject.total_shipper_count
    expect(total_shippers).to eq(2)
    end
    

    View Slide

75. describe "#total_shipper_count" do
    subject { described_class.new(store_orders: StoreOrder.all) }
    context "even division" do
    let!(:order1) { create_store_order(count_units: 4) }
    let!(:order2) { create_store_order(count_units: 8) }
    let!(:expected_total) { 3 }
    # ... lots of other tests ...
    it "returns order units summed, divided by units per shipper" do
    expect(subject.total_shipper_count).to eq(expected_total)
    end
    end
    end
    

    View Slide

76. context "rounding" do
    let!(:order) { create_store_order(count_units: 7) }
    let!(:expected_total) { 2 }
    # ... lots of other tests ...
    it "returns order units summed, divided by units per shipper" do
    expect(subject.total_shipper_count).to eq(expected_total)
    end
    end
    

    View Slide

77. IF YOUR TESTS ARE SUPER
    DUPLICATIVE, THAT’S
    ACTUALLY DESIGN FEEDBACK
    

    View Slide

78. SAY WHAT YOU MEAN,
    LITERALLY
    

    View Slide

79. def user_summary(user)
    "(#{user.id}) #{user.full_name}, #{user.role}"
    end
    

    View Slide

80. it "returns a user summary for printing" do
    user = User.new(id: 5, full_name: "Dave G", role: :admin)
    expected = "(#{user.id}) #{user.full_name}, #{user.role}"
    summary = user_summary(user)
    expect(summary).to eq(expected)
    end
    

    View Slide

81. it "returns a user summary for printing" do
    user = User.new(id: 5, full_name: "Dave G", role: :admin)
    summary = user_summary(user)
    expect(summary).to eq("(5) Dave G, admin")
    end
    

    View Slide

82. LEVERAGE YOUR TOOLS TO
    HELP GUIDE READERS
    

    View Slide

83. describe "#process" do
    it “has a correct return value"
    end
    describe "#process" do
    it "returns the number of records correctly persisted"
    end
    

    View Slide

84. describe CreateShipmentHistoryReport do
    describe "#sorted_shipments" do
    it "returns an empty array when there are no shipments"
    end
    end
    

    View Slide

85. rspec ./spec/services/create_shipment_history_report_spec.rb
    --format=‘documentation’
    CreateShipmentHistoryReport#sorted_shipments returns an empty array
    when there are no shipments
    

    View Slide

86. it “picks randomly, but correctly” do
    double1 = double
    double2 = double
    result = [double1, double2].sample
    expect(result).to eq(double1)
    end
    # expected: #
    # got: #
    

    View Slide

87. it “picks randomly, but correctly” do
    double1 = double("first record")
    double2 = double("second record”)
    result = [double1, double2].sample
    expect(result).to eq(double1)
    end
    # expected: #
    # got: #
    

    View Slide

88. it "checks result size" do
    arr = [1,2,3]
    response = arr.length
    expect(response > 3).to be_true
    end
    # expected true
    # got false
    

    View Slide

89. it "checks result size" do
    arr = [1,2,3]
    response = arr.length
    expect(response).to be > 3
    end
    # expected: > 3
    # got: 3
    

    View Slide

90. it "checks validity of a record" do
    thing = double(valid?: true)
    expect(thing.valid?).to be_false
    end
    # expected: false
    # got: true
    

    View Slide

91. it "checks validity of a record" do
    thing = double("order", valid?: true)
    expect(thing).not_to be_valid
    end
    # expected `#.valid?` to return false, got true
    

    View Slide

92. TESTS AS
    VERIFICATION
    

    View Slide

93. TEST WHAT’S COMPLICATED,
    RISKY, OR CHEAP
    

    View Slide

94. YOU CAN’T HAVE
    100% COVERAGE
    

    View Slide

95. DON’T TEST WHAT YOU
    DON’T OWN
    

    View Slide

96. class JobLog < ActiveRecord::Base
    validate :status, presence: true
    end
    it { should validate_presence_of(:status) }
    

    View Slide

97. class JobLog < ActiveRecord::Base
    validate :failure_message, presence: true, if: :failed?
    end
    it "requires failure_message for failures” do
    job = JobLog.new(status: :failed)
    expect(job).to validate_presence_of(:failure_message)
    job = JobLog.new(status: :completed)
    expect(job).not_to validate_presence_of(:failure_message)
    end
    

    View Slide

98. DON’T BE AFRAID TO
    DELETE YOUR TESTS
    

    View Slide

99. it "generates an array of strings” do
    expect(csv_data.length).to eq(shipments.length)
    expect(csv_data).to all(be_an(Array))
    end
    

    View Slide

100. BEWARE OF
     OVER-MOCKING
     

     View Slide

101. def user_summary(user)
     "(#{user.id}) #{user.full_name}, #{user.role}"
     end
     it "returns a user summary for printing, bad" do
     user = double(id: 5, full_name: "Dave G", role: :admin)
     response = user_summary(user)
     expect(response).to eq("(5) Dave G, admin")
     end
     

     View Slide

102. it "returns a user summary for printing, better" do
     user = instance_double(User, id: 5,
     full_name: "Dave G",
     role: :admin)
     response = user_summary(user)
     expect(response).to eq("(5) Dave G, admin")
     end
     

     View Slide

103. it "returns a user summary for printing, better" do
     user = User.new(id: 5,
     full_name: "Dave G",
     role: :admin)
     expect(user_summary(user)).to eq("(5) Dave G, admin")
     end
     

     View Slide

104. IN SUMMARY!
     

     View Slide

105. IT GETS EASIER
     WITH PRACTICE
     

     View Slide

106. 2. WRITE TESTS FOR HUMANS
     3. VERIFICATION COMES LAST
     1. USE TESTS TO DRIVE DESIGN
     

     View Slide

107. THANKS!
     

     View Slide