Mantendo a Sanidade Testando Estado

Apesar de ser uma ferramenta poderosa, Teste Baseado em Propriedades é muito pouco aplicado. Vou falar um pouco sobre a técnica e seus trade-offs, ferramentas para Elixir e contar um pouco sobre como estamos aplicando em nossos micro-serviços, stateful.

Transcript

1. MANTENDO SANIDADE TESTANDO ESTADO @_andrewhr
10. Telephony Engine
12. Call Control
13. Call Control App Comandos Webhooks
14. Call Control App
15. Call Control App POST /dial
16. Call Control App POST /dial {"event": "call_initiated"}
17. Call Control App POST /dial {"event": "call_initiated"} {"event”: "call_answered"}
19. PROPERTY-BASED TEST
20. PropEr
21. PBT 101
22. EXEMPLO
23. test "sorts a list" do assert Enum.sort([3, 1, 2]) == [1, 2, 3] end
24. test "sorts a list" do assert Enum.sort([3, 1, 2]) == [1, 2, 3] end
25. test "sorts a list" do assert Enum.sort([3, 1, 2]) == [1, 2, 3] end
26. test "sorts an empty list" do assert Enum.sort([]) == [] end
27. test "sorts an empty list" test "sorts a list with a single item" test "sorts a list multiple equal items" test "sorts a list huge numbers" test "sorts a list negative numbers" test "sorts a big list with lots of items"
28. PROPRIEDADE
29. property "sorts a list" do forall x <- list(integer()) do Enum.sort(x) |> Enum.chunk_every(2, 1, :discard) |> Enum.all?(fn [a, b] -> a <= b end) end end
30. property "sorts a list" do forall x <- list(integer()) do Enum.sort(x) |> Enum.chunk_every(2, 1, :discard) |> Enum.all?(fn [a, b] -> a <= b end) end end
31. property "sorts a list" do forall x <- list(integer()) do Enum.sort(x) |> Enum.chunk_every(2, 1, :discard) |> Enum.all?(fn [a, b] -> a <= b end) end end
32. GERADORES
33. property "sorts a list" do forall x <- list(integer()) do Enum.sort(x) |> Enum.chunk_every(2, 1, :discard) |> Enum.all?(fn [a, b] -> a <= b end) end end
34. list(integer())
35. map(number(), binary())
36. phone_number()
37. dial_command()
38. SHRINKING
39. property "sorts a list" do forall unsorted <- list(integer()) do unsorted |> Enum.chunk_every(2, 1, :discard) |> Enum.all?(fn [a, b] -> a <= b end) end end
40. Failed: After 11 test(s). [1,2,15,6] Shrinking ....(4 time(s)) [1,0]
41. [1,2,15,6]
42. [1,0]
43. STATEFUL
44. forall cmds <- commands(TestModel) do {history, state, result} = run_commands(TestModel, cmds) (result == :ok) |> aggregate(command_names(cmds)) |> when_fail(& report(cmds, state, result, history)) end
45. forall cmds <- commands(TestModel) do {history, state, result} = run_commands(TestModel, cmds) (result == :ok) |> aggregate(command_names(cmds)) |> when_fail(& report(cmds, state, result, history)) end
46. MODELO
47. DOMAIN-DRIVEN?
48. init_state/0 command/1 next_state/3 precondition/2
49. V1
50. V1 dial/1
51. V1 dial/1
52. V1 dial/1 answer/1 V2
53. V1 dial/1 answer/1 V2 V3 dial/1
54. V1 dial/1 answer/1 V2 V3 hangup/1 dial/1
55. def initial_state() do %{available: ["+551234567890", "+551234567894", "+551234567892"]} end
56. def command(%{available: numbers}) do return({:call, TestShim, :dial, [elements(numbers)]}) end
57. def command(%{ongoing: ids}) do [ {:call, TestShim, :answer, [elements(ids)]}, {:call, TestShim, :hangup, [elements(ids)]} ] |> oneof() end
58. def precondition(state, {:call, _, :dial, [number]}) do available?(state, number) end
59. def next_state(state, call_id, {:call, _, :dial, [number]}) do state |> acquire_call(call_id, number) |> set_call_state(call_id, :ringing) end
60. forall cmds <- commands(TestModel) do {history, state, result} = run_commands(TestModel, cmds) (result == :ok) |> aggregate(command_names(cmds)) |> when_fail(& report(cmds, state, result, history)) end
61. ESTADO
62. init_state/0 command/1 next_state/3 precondition/2 postcondition/3 :call FAIL
63. {:call, TestShim, :dial, [elements(numbers)]}
64. defmodule TestShim do def dial(number) do
 # magic goes here end end
65. defmodule TestShim do def dial(number) do
 dial = Repo.insert!(Dial.changeset(number)) dial.call_id end end
66. defmodule TestShim do def dial(number) do
 CallControl.dial(number) end end
67. defmodule TestShim do def dial(number) do # build client and payload
 case Tesla.post(client, "/dial", payload) do # process response and return call_id end end end
68. def postcondition(_state, {:call, _, :dial, [_]}, call_id) when is_binary(call_id) do true end
69. ASYNC
70. Call Control App Comandos Webhooks
71. Call Control App GenServer.call/2 GenServer.reply/2
72. defmodule TestShim do use GenServer def dial(number) do
 GenServer.call( __MODULE __, {:dial, number}) end end
73. def handle_call({:command, :dial, number}, from, state) do {:ok, call_id} = CallControl.dial(number) # update state {:noreply, state} end
74. def handle_cast({:webhook, webhook, call_id, resp}, state) do # descobre `ref` a partir dos parâmetros if ref, do: GenServer.reply(ref, resp) {:noreply, state} end
75. MUTABILIDADE
76. forall cmds <- commands(TestModel) do TestShim.setup_parties() {history, state, result} = run_commands(TestModel, cmds) (result == :ok) |> aggregate(command_names(cmds)) |> when_fail(& report(cmds, state, result, history)) end
77. forall cmds <- commands(TestModel) do TestShim.setup_parties() {history, state, result} = run_commands(TestModel, cmds) (result == :ok) |> aggregate(command_names(cmds)) |> when_fail(& report(cmds, state, result, history)) end
78. dial/1 answer/1 hangup/1 V1 V3
79. dial/1 answer/1 hangup/1 V1 V3
80. dial/1 answer/1 V3
81. def initial_state() do %{available: ["+551234567890", "+551234567894", "+551234567892"]} end
82. def initial_state() do %{init: ["+551234567890", "+551234567894", "+551234567892"]} end
83. def command(%{init: numbers}) do return({:call, TestShim, :setup_parties, []}) end
84. def next_state(state, _, {:call, _, :setup_parties, []}) do %{available: state[:init], ongoing: %{}, busy: %{}} end
85. CASOS PROBLEMA
86. def command(%{busy: numbers}) do return({:call, TestShim, :dial_busy, [elements(numbers)]}) end
87. def postcondition(_state, {:call, _, :dial_busy, [_]}, {:error, :call_rejected}) do true end
88. OK: Passed 100 test(s). 34% {'Elixir.CallControl.TestShim',dial,1} 21% {'Elixir.CallControl.TestShim',hangup,1} 19% {'Elixir.CallControl.TestShim',dial_busy,1} 13% {'Elixir.CallControl.TestShim',answer,1} 10% {'Elixir.CallControl.TestShim',setup_parties,0}
89. MUITOS TESTES!
90. DEMORA…
91. POWER-TOOL
92. ROI
93. Obrigado! @_andrewhr