Improve pseudo random seed state feature

config/config.exs

@@ -0,0 +1,5 @@
+use Mix.Config
+
+config :orangeade, default_start_seed: 1
+
+import_config "#{Mix.env()}.exs"

config/dev.exs

@@ -0,0 +1 @@
+use Mix.Config

config/prod.exs

@@ -0,0 +1 @@
+use Mix.Config

config/test.exs

@@ -0,0 +1,3 @@
+use Mix.Config
+
+config :orangeade, default_start_seed: ExUnit.configuration()[:seed]

lib/orangeade.ex

@@ -20,6 +20,10 @@ defmodule Orangeade do
   defdelegate term(), to: Gen.Term, as: :stream
 
   def start(_type, _args) do
-    Orangeade.Supervisor.start_link(1)
+    Orangeade.Application.Supervisor.start_link(start_seed: get_default_seed())
+  end
+
+  defp get_default_seed do
+    Application.get_env(:orangeade, :default_start_seed)
   end
 end

lib/orangeade/seed_state.ex → lib/orangeade/application/seed_state.ex

@@ -1,4 +1,4 @@
-defmodule Orangeade.SeedState do
+defmodule Orangeade.Application.SeedState do
   use Agent
 
   alias Psi.LinearCongruentialGenerator, as: LCG
@@ -7,12 +7,12 @@ defmodule Orangeade.SeedState do
   Starts a new seed state which is a big natural numbers stream which is created
   with start_seed passed by supervisor.
   """
-  def start_link(start_seed: start_seed) do
+  def start_link(start_seed: seed) do
     Agent.start_link(
       fn ->
         LCG.stream(
           generator: Orangeade.Generator.BigNatural.instance(),
-          seed: start_seed
+          seed: seed
         )
       end,
       name: __MODULE__

lib/orangeade/application/supervisor.ex

@@ -0,0 +1,18 @@
+defmodule Orangeade.Application.Supervisor do
+  use Supervisor
+
+  def start_link(start_seed: seed) do
+    Supervisor.start_link(__MODULE__, seed)
+  end
+
+  def init(seed) do
+    children = [
+      %{
+        id: SeedState,
+        start: {Orangeade.Application.SeedState, :start_link, [[start_seed: seed]]}
+      }
+    ]
+
+    Supervisor.init(children, strategy: :one_for_one)
+  end
+end

lib/orangeade/generator/big_natural.ex

@@ -2,7 +2,7 @@ defmodule Orangeade.Generator.BigNatural do
   alias Psi.LinearCongruentialGenerator, as: LCG
 
   def stream() do
-    alias Orangeade.SeedState
+    alias Orangeade.Application.SeedState
 
     seed = SeedState.get_next()
     LCG.stream(generator: Orangeade.Generator.BigNatural.instance(), seed: seed)

lib/orangeade/generator/bound_natural.ex

@@ -1,7 +1,7 @@
 defmodule Orangeade.Generator.BoundNatural do
   def stream(limit: i) do
     alias Psi.LinearCongruentialGenerator, as: LCG
-    alias Orangeade.SeedState
+    alias Orangeade.Application.SeedState
 
     seed = SeedState.get_next()
     s = LCG.stream(generator: Orangeade.Generator.BigNatural.instance(), seed: seed)

test/orangeade/seed_state_test.exs → test/orangeade/application/seed_state_test.exs

@@ -1,7 +1,7 @@
-defmodule Orangeade.SeedStateTest do
+defmodule Orangeade.Application.SeedStateTest do
   use ExUnit.Case
 
-  alias Orangeade.SeedState
+  alias Orangeade.Application.SeedState
 
   test "Check if each next seed from get_next/1 is different" do
     list_of_seeds = for _n <- 1..100, do: SeedState.get_next()

test/orangeade/generator/big_natural_test.exs

@@ -1,16 +1,20 @@
 defmodule Orangeade.Generator.BigNaturalTest do
-  use ExUnit.Case, async: true
-  import Orangeade.Generator.BigNatural, only: [stream: 0]
+  use ExUnit.Case
+  alias Orangeade.Generator.BigNatural
 
-  test "check 5 first generated elements" do
-    generated = Caffeine.Stream.take(stream(), 5)
+  test "generated elements are always natural" do
+    list_of_elements =
+      BigNatural.stream()
+      |> Caffeine.Stream.take(10)
 
-    assert generated == [
-             1,
-             7_806_831_264_735_756_412,
-             9_396_908_728_118_811_419,
-             11_960_119_808_228_829_710,
-             7_062_582_979_898_595_269
-           ]
+    assert Enum.all?(list_of_elements, &is_natural/1)
+  end
+
+  defp is_natural(n) when n >= 0 do
+    true
+  end
+
+  defp is_natural(_n) do
+    false
   end
 end

test/test_helper.exs

@@ -1 +1,2 @@
-ExUnit.start()
+seed = Application.get_env(:orangeade, :default_start_seed)
+ExUnit.start(seed: seed)