Introduce property testing

lib/weather_loop/snapshot_conversions.ex

@@ -5,8 +5,7 @@ defmodule WeatherLoop.SnapshotConversions do
     |> round
   end
 
-  def cardinal_direction(nil), do: nil
-  def cardinal_direction(direction_degrees) do
+  def cardinal_direction(direction_degrees) when is_integer(direction_degrees) do
     case direction_degrees do
       x when x in 0..11 ->
         "N"
@@ -42,15 +41,21 @@ defmodule WeatherLoop.SnapshotConversions do
         "NNW"
       x when x in 349..360 ->
         "N"
+      _ ->
+        nil
     end
   end
+  def cardinal_direction(_), do: nil
 
   def wind_detail(nil, nil), do: nil
   def wind_detail(wind_direction, wind_speed) do
     "#{cardinal_direction(wind_direction)} at #{round(wind_speed)} mph"
   end
 
   def convert_epoch(nil), do: nil
+  def convert_epoch(epoch) when is_float(epoch), do: nil
+  def convert_epoch(epoch) when epoch < 0, do: nil
+  def convert_epoch(epoch) when epoch > 2147483647, do: nil
   def convert_epoch(epoch) do
     {:ok, time_string} =
       Calendar.DateTime.Parse.unix!(epoch)

mix.exs

@@ -58,7 +58,8 @@ defmodule WeatherLoop.MixProject do
       {:hackney, "~> 1.17"},
       {:tzdata, "~> 1.1"},
       {:calendar, "~> 1.0.0"},
-      {:tailwind, "~> 0.1", runtime: Mix.env() == :dev}
+      {:tailwind, "~> 0.1", runtime: Mix.env() == :dev},
+      {:propcheck, "~> 1.4", only: [:test, :dev]}
     ]
   end
 

mix.lock

@@ -24,6 +24,7 @@
   "ibrowse": {:hex, :ibrowse, "4.4.0", "2d923325efe0d2cb09b9c6a047b2835a5eda69d8a47ed6ff8bc03628b764e991", [:rebar3], [], "hexpm", "6a8e5988872086f0506bef68311493551ac5beae7c06ba2a00d5e9f97a60f1c2"},
   "idna": {:hex, :idna, "6.1.1", "8a63070e9f7d0c62eb9d9fcb360a7de382448200fbbd1b106cc96d3d8099df8d", [:rebar3], [{:unicode_util_compat, "~>0.7.0", [hex: :unicode_util_compat, repo: "hexpm", optional: false]}], "hexpm", "92376eb7894412ed19ac475e4a86f7b413c1b9fbb5bd16dccd57934157944cea"},
   "jason": {:hex, :jason, "1.3.0", "fa6b82a934feb176263ad2df0dbd91bf633d4a46ebfdffea0c8ae82953714946", [:mix], [{:decimal, "~> 1.0 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "53fc1f51255390e0ec7e50f9cb41e751c260d065dcba2bf0d08dc51a4002c2ac"},
+  "libgraph": {:hex, :libgraph, "0.16.0", "3936f3eca6ef826e08880230f806bfea13193e49bf153f93edcf0239d4fd1d07", [:mix], [], "hexpm", "41ca92240e8a4138c30a7e06466acc709b0cbb795c643e9e17174a178982d6bf"},
   "metrics": {:hex, :metrics, "1.0.1", "25f094dea2cda98213cecc3aeff09e940299d950904393b2a29d191c346a8486", [:rebar3], [], "hexpm", "69b09adddc4f74a40716ae54d140f93beb0fb8978d8636eaded0c31b6f099f16"},
   "mime": {:hex, :mime, "2.0.2", "0b9e1a4c840eafb68d820b0e2158ef5c49385d17fb36855ac6e7e087d4b1dcc5", [:mix], [], "hexpm", "e6a3f76b4c277739e36c2e21a2c640778ba4c3846189d5ab19f97f126df5f9b7"},
   "mimerl": {:hex, :mimerl, "1.2.0", "67e2d3f571088d5cfd3e550c383094b47159f3eee8ffa08e64106cdf5e981be3", [:rebar3], [], "hexpm", "f278585650aa581986264638ebf698f8bb19df297f66ad91b18910dfc6e19323"},
@@ -40,6 +41,8 @@
   "plug_cowboy": {:hex, :plug_cowboy, "2.5.2", "62894ccd601cf9597e2c23911ff12798a8a18d237e9739f58a6b04e4988899fe", [:mix], [{:cowboy, "~> 2.7", [hex: :cowboy, repo: "hexpm", optional: false]}, {:cowboy_telemetry, "~> 0.3", [hex: :cowboy_telemetry, repo: "hexpm", optional: false]}, {:plug, "~> 1.7", [hex: :plug, repo: "hexpm", optional: false]}], "hexpm", "ea6e87f774c8608d60c8d34022a7d073bd7680a0a013f049fc62bf35efea1044"},
   "plug_crypto": {:hex, :plug_crypto, "1.2.2", "05654514ac717ff3a1843204b424477d9e60c143406aa94daf2274fdd280794d", [:mix], [], "hexpm", "87631c7ad914a5a445f0a3809f99b079113ae4ed4b867348dd9eec288cecb6db"},
   "postgrex": {:hex, :postgrex, "0.16.3", "fac79a81a9a234b11c44235a4494d8565303fa4b9147acf57e48978a074971db", [:mix], [{:connection, "~> 1.1", [hex: :connection, repo: "hexpm", optional: false]}, {:db_connection, "~> 2.1", [hex: :db_connection, repo: "hexpm", optional: false]}, {:decimal, "~> 1.5 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}, {:table, "~> 0.1.0", [hex: :table, repo: "hexpm", optional: true]}], "hexpm", "aeaae1d2d1322da4e5fe90d241b0a564ce03a3add09d7270fb85362166194590"},
+  "propcheck": {:hex, :propcheck, "1.4.1", "c12908dbe6f572032928548089b34ff9d40672d5d70f1562e3a9e9058d226cc9", [:mix], [{:libgraph, "~> 0.13", [hex: :libgraph, repo: "hexpm", optional: false]}, {:proper, "~> 1.4", [hex: :proper, repo: "hexpm", optional: false]}], "hexpm", "e1b088f574785c3c7e864da16f39082d5599b3aaf89086d3f9be6adb54464b19"},
+  "proper": {:hex, :proper, "1.4.0", "89a44b8c39d28bb9b4be8e4d715d534905b325470f2e0ec5e004d12484a79434", [:rebar3], [], "hexpm", "18285842185bd33efbda97d134a5cb5a0884384db36119fee0e3cfa488568cbb"},
   "ranch": {:hex, :ranch, "1.8.0", "8c7a100a139fd57f17327b6413e4167ac559fbc04ca7448e9be9057311597a1d", [:make, :rebar3], [], "hexpm", "49fbcfd3682fab1f5d109351b61257676da1a2fdbe295904176d5e521a2ddfe5"},
   "ssl_verify_fun": {:hex, :ssl_verify_fun, "1.1.6", "cf344f5692c82d2cd7554f5ec8fd961548d4fd09e7d22f5b62482e5aeaebd4b0", [:make, :mix, :rebar3], [], "hexpm", "bdb0d2471f453c88ff3908e7686f86f9be327d065cc1ec16fa4540197ea04680"},
   "swoosh": {:hex, :swoosh, "1.7.1", "53bb5b8efaf5577bbad1480fb057d8bcb7b16097aa015ab9f369a01592c961ec", [:mix], [{:cowboy, "~> 1.1 or ~> 2.4", [hex: :cowboy, repo: "hexpm", optional: true]}, {:ex_aws, "~> 2.1", [hex: :ex_aws, repo: "hexpm", optional: true]}, {:finch, "~> 0.6", [hex: :finch, repo: "hexpm", optional: true]}, {:gen_smtp, "~> 0.13 or ~> 1.0", [hex: :gen_smtp, repo: "hexpm", optional: true]}, {:hackney, "~> 1.9", [hex: :hackney, repo: "hexpm", optional: true]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}, {:mail, "~> 0.2", [hex: :mail, repo: "hexpm", optional: true]}, {:mime, "~> 1.1 or ~> 2.0", [hex: :mime, repo: "hexpm", optional: false]}, {:plug_cowboy, ">= 1.0.0", [hex: :plug_cowboy, repo: "hexpm", optional: true]}, {:telemetry, "~> 0.4.2 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "8206d7da5038f0e11292b775b7e588fcd5dc74ac4dd8b661fe72f58207234747"},

test/weather_loop/snapshot_conversions_property_test.exs

@@ -0,0 +1,61 @@
+defmodule WeatherLoop.SnapshotConversionsPropertyTest do
+  use ExUnit.Case
+  use PropCheck
+  alias WeatherLoop.SnapshotConversions
+
+  property ".cardinal_direction is string when valid" do
+    forall type <- range(0, 360) do
+      (SnapshotConversions.cardinal_direction(type) |> Kernel.is_binary) == true
+    end
+  end
+
+  property ".cardinal_direction is nil when negative" do
+    forall type <- neg_integer() do
+      SnapshotConversions.cardinal_direction(type) == nil
+    end
+  end
+
+  property ".cardinal_direction is nil when over 360" do
+    forall type <- range(361, 10000) do
+      SnapshotConversions.cardinal_direction(type) == nil
+    end
+  end
+
+  property ".cardinal_direction is nil when float" do
+    forall type <- float() do
+      SnapshotConversions.cardinal_direction(type) == nil
+    end
+  end
+
+  property ".convert_epoch is string when valid" do
+    forall epoch <- range(100000000, 200000000) do
+      SnapshotConversions.convert_epoch(epoch) |> Kernel.is_binary == true
+    end
+  end
+
+  property ".convert_epoch is nil when negative" do
+    forall epoch <- neg_integer() do
+      SnapshotConversions.convert_epoch(epoch) == nil
+    end
+  end
+
+  property ".convert_epoch is nil when float" do
+    forall epoch <- float() do
+      SnapshotConversions.convert_epoch(epoch) == nil
+    end
+  end
+
+  property ".convert_epoch is nil post epoch" do
+    forall epoch <- range(year_one_post_epoch(), year_ten_post_epoch()) do
+      SnapshotConversions.convert_epoch(epoch) == nil
+    end
+  end
+
+  def year_one_post_epoch do
+    Enum.random(2147483648..2179019647)
+  end
+
+  def year_ten_post_epoch do
+    Enum.random(2463016447..2494638847)
+  end
+end