Property based testing with StreamData

.formatter.exs

@@ -1,5 +1,5 @@
 [
-  import_deps: [:ecto, :phoenix],
+  import_deps: [:ecto, :phoenix, :stream_data],
   inputs: ["*.{ex,exs}", "priv/*/seeds.exs", "{config,lib,test}/**/*.{ex,exs}"],
   subdirectories: ["priv/*/migrations"]
 ]

README.md

@@ -3,4 +3,40 @@ Welcome to Elixir School's workshop on Real-Time Phoenix with Channels, PubSub,
 
 Collaborators can sign in with a username and click a button to start the "pointing party". Tickets are displayed for estimation and each user can cast their store point estimate vote. Once all the votes are cast, a winner is declared and the participants can move on to estimate the next ticket.
 
-The master branch of this app represents the starting state of the code for this workshop. Clone down and make sure you're on the master branch in order to follow along. 
+The master branch of this app represents the starting state of the code for this workshop. Clone down and make sure you're on the master branch in order to follow along.
+
+## Resources
+
+### Phoenix Channels
+
+* [Official guide](https://hexdocs.pm/phoenix/channels.html)
+* [API documentation](https://hexdocs.pm/phoenix/Phoenix.Channel.html#content)
+
+### Phoenix PubSub
+
+* [API documentation](https://hexdocs.pm/phoenix_pubsub/Phoenix.PubSub.html)
+
+### Phoenix LiveView
+
+* [LiveView announcement](https://dockyard.com/blog/2018/12/12/phoenix-liveview-interactive-real-time-apps-no-need-to-write-javascript) by Chris McCord
+* [API documentation](https://hexdocs.pm/phoenix_live_view/Phoenix.LiveView.html)
+* ["Walk-Through of Phoenix LiveView"](https://elixirschool.com/blog/phoenix-live-view/) by Sophie DeBenedetto
+* ["Building Real-Time Features with Phoenix Live View and PubSub"](https://elixirschool.com/blog/live-view-with-pub-sub/) by Sophie DeBenedetto
+* ["Using Channels with LiveView for Better UX"](https://elixirschool.com/blog/live-view-with-channels/) by Sophie DeBenedetto
+* ["Tracking Users in a Chat App with LiveView, PubSub Presence"](https://elixirschool.com/blog/live-view-with-presence/) by Sophie DeBenedetto
+
+### Property-based Testing and StreamData
+
+* [StreamData on GitHub](https://github.com/whatyouhide/stream_data)
+* [StreamData documentation](https://hexdocs.pm/stream_data/StreamData.html)
+* [Elixir School article on StreamData](https://elixirschool.com/en/lessons/libraries/stream-data/)
+* [_Property-Based Testing with PropEr, Erlang, and Elixir_ and _PropEr Testing_](https://propertesting.com/) by Fred Hebert
+* ["An introduction to property-based testing"](https://fsharpforfunandprofit.com/posts/property-based-testing/) by Scott Wlaschin
+* ["Choosing properties for property-based testing"](https://fsharpforfunandprofit.com/posts/property-based-testing-2/) by Scott Wlaschin
+
+### Estimation
+
+* [_Agile Estimating and Planning_](https://www.mountaingoatsoftware.com/books/agile-estimating-and-planning) by Mike Cohn of Mountain Goat Software
+* [planningpoker.com](https://www.planningpoker.com/) is a full-featured estimation tool that may work well for your team.
+
+Thanks to James Grenning and Mike Cohn for their inspiration and their work in software estimation!

config/cards.exs

@@ -15,7 +15,6 @@ config :pointing_party,
       Update the application to save an individual's vote and the final card points to the database.
       """
     },
-
     %{
       title: "Add Guardian dependency",
       description: """
@@ -34,5 +33,5 @@ config :pointing_party,
       description: """
       Update our existing authentication flow to use the newly created Auth module.
       """
-    },
+    }
   ]

lib/pointing_party/account.ex

@@ -11,6 +11,7 @@ defmodule PointingParty.Account do
 
   def create(attrs) do
     changeset = changeset(%Account{}, attrs)
+
     if changeset.valid? do
       account = apply_changes(changeset)
       {:ok, account}

lib/pointing_party/vote_calculator.ex

@@ -19,11 +19,7 @@ defmodule PointingParty.VoteCalculator do
   end
 
   defp get_points(score_card, users) do
-    votes =
-      users
-      |> Enum.map(fn {_username, %{metas: [%{points: points}]}} ->
-        points
-      end)
+    votes = Enum.map(users, fn {_username, %{metas: [%{points: points}]}} -> points end)
 
     update_score_card(score_card, :votes, votes)
   end
@@ -57,9 +53,10 @@ defmodule PointingParty.VoteCalculator do
 
   defp handle_tie(%{majority: nil, calculated_votes: calculated_votes}) do
     calculated_votes
-    |> Enum.sort_by(&elem(&1, 1))
-    |> Enum.take(2)
+    |> Enum.sort_by(&elem(&1, 1), &>=/2)
     |> Enum.map(&elem(&1, 0))
+    |> Enum.sort()
+    |> Enum.take(2)
   end
 
   defp handle_tie(%{majority: majority}), do: majority

lib/pointing_party_web/channels/presence.ex

@@ -1,4 +1,5 @@
 defmodule PointingPartyWeb.Presence do
-  use Phoenix.Presence, otp_app: :pointing_party,
-                        pubsub_server: PointingParty.PubSub
+  use Phoenix.Presence,
+    otp_app: :pointing_party,
+    pubsub_server: PointingParty.PubSub
 end

lib/pointing_party_web/channels/room_channel.ex

@@ -32,6 +32,7 @@ defmodule PointingPartyWeb.RoomChannel do
   end
 
   defp initialize_state(%{assigns: %{cards: _cards}} = socket), do: socket
+
   defp initialize_state(socket) do
     [first | cards] = Card.cards()
 

lib/pointing_party_web/controllers/session_controller.ex

@@ -15,13 +15,13 @@ defmodule PointingPartyWeb.SessionController do
         |> put_session(:username, username)
         |> redirect(to: "/cards")
         |> halt()
+
       {:error, changeset} ->
         render(conn, "new.html", changeset: changeset)
     end
   end
 
   def delete(conn, _params) do
-    clear_session(conn)
-    |> redirect(to: "/login") |> halt()
+    clear_session(conn) |> redirect(to: "/login") |> halt()
   end
 end

lib/pointing_party_web/plugs/auth.ex

@@ -12,6 +12,6 @@ defmodule PointingPartyWeb.Plugs.Auth do
   end
 
   defp authenticate(conn) do
-     get_session(conn, :username)
+    get_session(conn, :username)
   end
 end

mix.exs

@@ -41,7 +41,9 @@ defmodule PointingParty.MixProject do
       {:gettext, "~> 0.11"},
       {:jason, "~> 1.0"},
       {:plug_cowboy, "~> 2.0"},
-      {:ex_machina, "~> 2.3", only: :test}
+      {:ex_machina, "~> 2.3", only: :test},
+      {:mix_test_watch, "~> 0.8", only: :dev, runtime: false},
+      {:stream_data, "~> 0.1", only: :test}
     ]
   end
 end

mix.lock

@@ -11,6 +11,7 @@
   "gettext": {:hex, :gettext, "0.17.0", "abe21542c831887a2b16f4c94556db9c421ab301aee417b7c4fbde7fbdbe01ec", [:mix], [], "hexpm"},
   "jason": {:hex, :jason, "1.1.2", "b03dedea67a99223a2eaf9f1264ce37154564de899fd3d8b9a21b1a6fd64afe7", [:mix], [{:decimal, "~> 1.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm"},
   "mime": {:hex, :mime, "1.3.1", "30ce04ab3175b6ad0bdce0035cba77bba68b813d523d1aac73d9781b4d193cf8", [:mix], [], "hexpm"},
+  "mix_test_watch": {:hex, :mix_test_watch, "0.9.0", "c72132a6071261893518fa08e121e911c9358713f62794a90c95db59042af375", [:mix], [{:file_system, "~> 0.2.1 or ~> 0.3", [hex: :file_system, repo: "hexpm", optional: false]}], "hexpm"},
   "phoenix": {:hex, :phoenix, "1.4.9", "746d098e10741c334d88143d3c94cab1756435f94387a63441792e66ec0ee974", [:mix], [{:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}, {:phoenix_pubsub, "~> 1.1", [hex: :phoenix_pubsub, repo: "hexpm", optional: false]}, {:plug, "~> 1.8.1 or ~> 1.9", [hex: :plug, repo: "hexpm", optional: false]}, {:plug_cowboy, "~> 1.0 or ~> 2.0", [hex: :plug_cowboy, repo: "hexpm", optional: true]}, {:telemetry, "~> 0.4", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm"},
   "phoenix_ecto": {:hex, :phoenix_ecto, "4.0.0", "c43117a136e7399ea04ecaac73f8f23ee0ffe3e07acfcb8062fe5f4c9f0f6531", [:mix], [{:ecto, "~> 3.0", [hex: :ecto, repo: "hexpm", optional: false]}, {:phoenix_html, "~> 2.9", [hex: :phoenix_html, repo: "hexpm", optional: true]}, {:plug, "~> 1.0", [hex: :plug, repo: "hexpm", optional: false]}], "hexpm"},
   "phoenix_html": {:hex, :phoenix_html, "2.13.3", "850e292ff6e204257f5f9c4c54a8cb1f6fbc16ed53d360c2b780a3d0ba333867", [:mix], [{:plug, "~> 1.5", [hex: :plug, repo: "hexpm", optional: false]}], "hexpm"},
@@ -21,5 +22,6 @@
   "plug_crypto": {:hex, :plug_crypto, "1.0.0", "18e49317d3fa343f24620ed22795ec29d4a5e602d52d1513ccea0b07d8ea7d4d", [:mix], [], "hexpm"},
   "postgrex": {:hex, :postgrex, "0.14.3", "5754dee2fdf6e9e508cbf49ab138df964278700b764177e8f3871e658b345a1e", [:mix], [{:connection, "~> 1.0", [hex: :connection, repo: "hexpm", optional: false]}, {:db_connection, "~> 2.0", [hex: :db_connection, repo: "hexpm", optional: false]}, {:decimal, "~> 1.5", [hex: :decimal, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}], "hexpm"},
   "ranch": {:hex, :ranch, "1.7.1", "6b1fab51b49196860b733a49c07604465a47bdb78aa10c1c16a3d199f7f8c881", [:rebar3], [], "hexpm"},
+  "stream_data": {:hex, :stream_data, "0.4.3", "62aafd870caff0849a5057a7ec270fad0eb86889f4d433b937d996de99e3db25", [:mix], [], "hexpm"},
   "telemetry": {:hex, :telemetry, "0.4.0", "8339bee3fa8b91cb84d14c2935f8ecf399ccd87301ad6da6b71c09553834b2ab", [:rebar3], [], "hexpm"},
 }

priv/repo/migrations/20190708014847_create_cards.exs

@@ -3,11 +3,10 @@ defmodule PointingParty.Repo.Migrations.CreateCards do
 
   def change do
     create table(:cards) do
-      add :title, :string
-      add :description, :string
+      add(:title, :string)
+      add(:description, :string)
 
       timestamps()
     end
-
   end
 end

priv/repo/migrations/20190714140153_add_points_to_cards.exs

@@ -3,7 +3,7 @@ defmodule PointingParty.Repo.Migrations.AddPointsToCards do
 
   def change do
     alter table("cards") do
-      add :points, :integer, default: 0
+      add(:points, :integer, default: 0)
     end
   end
 end

priv/repo/seeds.exs

@@ -10,7 +10,6 @@
 # We recommend using the bang functions (`insert!`, `update!`
 # and so on) as they will fail if something goes wrong.
 
-
 alias PointingParty.{Card, Repo}
 
 cards = [
@@ -21,7 +20,7 @@ cards = [
   %{title: "Fifth card", description: "This is a description of the fifth card."},
   %{title: "Sixth card", description: "This is a description of the sixth card."},
   %{title: "Seventh card", description: "This is a description of the seventh card."},
-  %{title: "Eighth card", description: "This is a description of the eighth card."},
+  %{title: "Eighth card", description: "This is a description of the eighth card."}
 ]
 
 Enum.each(cards, fn card ->

test/pointing_party/vote_calculator_test.exs

@@ -1,23 +1,96 @@
 defmodule PointingParty.VoteCalculatorTest do
   use ExUnit.Case, async: true
+  use ExUnitProperties
 
-   @users_with_winner %{
-    "sean" => %{metas: [%{points: 1}]},
-    "michael" => %{metas: [%{points: 3}]},
-    "sophie" => %{metas: [%{points: 3}]}
-   }
+  alias PointingParty.{Card, VoteCalculator}
 
-  @users_with_tie %{
-   "sean" => %{metas: [%{points: 1}]},
-   "michael" => %{metas: [%{points: 2}]},
-   "sophie" => %{metas: [%{points: 3}]}
-  }
+  # Properties
+  # --------------
+  # When there is a tie, the result will be a list
+  # The tie list will be sorted in increasing order
+  # The tie list will contain unique elements
+  # The tie list will have exactly two elements
+  # The tie list contains only integers
+  # The tie list integers must be valid voting options
+  # The greatest element in the tie list will not be greater than the highest vote
+  #
+  # When there is a winner, the result will be an integer
+  # When there is a winner, the result will be one of the valid voting options
+  # When there is a winner, it will not be greater than the highest vote
+  #
+  # Notes
+  # --------------
+  # Ties can happen when there are even or odd numbers of players
+  # Winning votes can also have an even or odd number of players
+  # Single-player games will always have a winner
 
-  test "calculate_votes/1 calculates when there is a winner" do
-    {"winner", 3} = PointingParty.VoteCalculator.calculate_votes(@users_with_winner)
-  end
 
-  test "calculate_votes/1 calculates when there is a tie" do
-    {"tie", [1,2]} = PointingParty.VoteCalculator.calculate_votes(@users_with_tie)
+  describe "calculate_votes/1" do
+    setup do
+      points_map = fixed_map(%{
+        points: member_of(Card.points_range())
+      })
+      metas_map = fixed_map(%{
+        metas: list_of(points_map, length: 1)
+      })
+      user_generator = nonempty(map_of(string(:alphanumeric), metas_map))
+
+      [user_generator: user_generator]
+    end
+
+    property "calculated vote is a list or an integer", %{user_generator: user_generator} do
+      check all users <- user_generator,
+                {_event, winner} = VoteCalculator.calculate_votes(users),
+                max_runs: 20 do
+        assert is_list(winner) || is_integer(winner)
+      end
+    end
+
+    property "the winning value is not more than the highest vote", %{user_generator: user_generator} do
+      check all users <- user_generator,
+                max_runs: 20 do
+        max_vote =
+          users
+          |> Enum.map(fn {_username, %{metas: [%{points: points}]}} -> points end)
+          |> Enum.max()
+
+        case PointingParty.VoteCalculator.calculate_votes(users) do
+          {"winner", winner} -> assert winner <= max_vote
+          {"tie", [_lesser, greater]} -> assert greater <= max_vote
+        end
+      end
+    end
+
+    property "when there is a winner, calculated vote is a valid integer", %{user_generator: user_generator} do
+      check all users <- user_generator,
+                {event, winner} = PointingParty.VoteCalculator.calculate_votes(users),
+                max_runs: 20 do
+        if event == "winner" do
+          assert winner in Card.points_range()
+        end
+      end
+    end
+
+    property "when there is a tie, calculated vote is a list with two sorted values", %{user_generator: user_generator} do
+      check all users <- user_generator,
+                {event, votes} = PointingParty.VoteCalculator.calculate_votes(users),
+                max_runs: 20 do
+        if event == "tie" do
+          [lesser, greater] = votes
+
+          assert lesser < greater
+        end
+      end
+    end
+
+    property "when there is a tie, calculated vote is a list of valid integers", %{user_generator: user_generator} do
+      check all users <- user_generator,
+                {event, votes} = PointingParty.VoteCalculator.calculate_votes(users),
+                max_runs: 20 do
+        if event == "tie" do
+          assert Enum.all?(votes, fn vote -> vote in Card.points_range() end)
+        end
+      end
+    end
   end
 end

test/pointing_party_web/controllers/card_controller_test.exs

@@ -4,7 +4,7 @@ defmodule PointingPartyWeb.CardControllerTest do
   @username "test_user"
 
   describe "authenticated user" do
-    setup  %{conn: conn} do
+    setup %{conn: conn} do
       auth_conn = Plug.Test.init_test_session(conn, username: @username)
       {:ok, %{conn: auth_conn}}
     end

test/pointing_party_web/controllers/page_controller_test.exs

@@ -4,9 +4,9 @@ defmodule PointingPartyWeb.PageControllerTest do
   @username "test_user"
 
   describe "authenticated user" do
-    setup  %{conn: conn} do
-      conn = conn
-      |> Plug.Conn.assign(:username, @username)
+    setup %{conn: conn} do
+      conn = Plug.Conn.assign(conn, :username, @username)
+
       {:ok, %{conn: conn}}
     end