Property-based testing with Stream Data for VoteCalculator

Author: SophieDeBenedetto

.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"]
 ]

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_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 +41,8 @@ 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},
+      {:stream_data, "~> 0.1", only: :test}
     ]
   end
 end

mix.lock

@@ -21,5 +21,6 @@
   "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 +1,84 @@
 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}]}
-   }
+  describe "calculate_votes/1" do
+    setup do
+      points_map = fixed_map(%{points: integer(1..5)})
 
-  @users_with_tie %{
-   "sean" => %{metas: [%{points: 1}]},
-   "michael" => %{metas: [%{points: 2}]},
-   "sophie" => %{metas: [%{points: 3}]}
-  }
+      metas_map =
+        fixed_map(%{
+          metas: list_of(points_map, length: 1)
+        })
 
-  test "calculate_votes/1 calculates when there is a winner" do
-    {"winner", 3} = PointingParty.VoteCalculator.calculate_votes(@users_with_winner)
-  end
+      users = nonempty(map_of(string(:alphanumeric), metas_map))
+      [users: users]
+    end
+
+    property "winning value is a list or a integer", %{users: users} do
+      check all users <- users do
+        {_event, winner} = PointingParty.VoteCalculator.calculate_votes(users)
+        assert is_list(winner) || is_integer(winner)
+      end
+    end
+
+    property "tie when winning value is a list, winner when winning value is an integer", %{users: users} do
+      check all users <- users do
+        {event, winner} = PointingParty.VoteCalculator.calculate_votes(users)
+
+        cond do
+          is_list(winner) ->
+            assert event == "tie"
+
+          is_integer(winner) ->
+            assert event == "winner"
+        end
+      end
+    end
+
+    property "the winning value is not more than the highest point value", %{users: users} do
+      check all users <- users do
+        {_event, winner} = PointingParty.VoteCalculator.calculate_votes(users)
+
+        max_vote =
+          users
+          |> Enum.map(fn {_username, %{metas: [%{points: points}]}} -> points end)
+          |> Enum.max()
+
+        cond do
+          is_list(winner) ->
+            assert Enum.max(winner) <= max_vote
+
+          is_integer(winner) ->
+            assert winner <= max_vote
+        end
+      end
+    end
+
+    property "when the winner is a list of two sorted values", %{users: users} do
+      check all users <- users do
+        {_event, winner} = PointingParty.VoteCalculator.calculate_votes(users)
+
+        if is_list(winner) do
+          assert length(winner) == 2
+
+          votes = Enum.map(users, fn {_username, %{metas: [%{points: points}]}} -> points end)
+
+          calculated_votes =
+            Enum.reduce(votes, %{}, fn vote, acc ->
+              value = (acc[vote] || 0) + 1
+              Map.put(acc, vote, value)
+            end)
+
+          sorted =
+            calculated_votes
+            |> Enum.sort_by(fn ({_k, v}) -> v end)
+            |> Enum.map(fn ({a, _b}) -> a end)
+            |> Enum.take(2)
 
-  test "calculate_votes/1 calculates when there is a tie" do
-    {"tie", [1,2]} = PointingParty.VoteCalculator.calculate_votes(@users_with_tie)
+          assert sorted == winner
+        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