add test stack

lib/stack.ex

@@ -0,0 +1,19 @@
+defmodule MyStack do
+  use GenServer
+
+  def start_link(args) do
+    GenServer.start_link(__MODULE__, nil, name: args[:name])
+  end
+
+  def init(_) do
+    {:ok, []}
+  end
+
+  def handle_info({:push, el}, state) do
+    {:noreply, [el] ++ state}
+  end
+
+  def handle_call(:pop, _from, [head | tail]) do
+    {:reply, head, tail}
+  end
+end

test/test_helper.exs

@@ -0,0 +1 @@
+ExUnit.start()

test/test_stack.exs

@@ -0,0 +1,40 @@
+defmodule MyStack.Test do
+
+  require MyStack
+
+  use ExUnit.Case, async: true
+  
+  defmodule MySupervisor do
+    use Supervisor
+
+    def start_link do
+      Supervisor.start_link(__MODULE__, :ok)
+    end
+
+    def init(:ok) do
+      children = [
+        %{id: 1, start: {MyStack, :start_link, [[name: :my_server]]}},
+        %{id: 2, start: {MyStack, :start_link, [[name: :my_server2]]}}
+      ]
+
+      Supervisor.init(children, strategy: :one_for_one)
+    end
+  end
+
+  setup do
+    {:ok, supervisor: MySupervisor.start_link()}
+  end
+
+  test "server starts with an empty client list", %{supervisor: supervisor} do
+    send(:my_server, {:push, 2})
+    assert GenServer.call(:my_server, :pop) == 2
+    send(:my_server, {:push, 1})
+    send(:my_server, {:push, 4})
+    send(:my_server2, {:push, 3})
+    send(:my_server2, {:push, 8})
+    assert GenServer.call(:my_server2, :pop) == 8
+    assert GenServer.call(:my_server, :pop) == 4
+    assert GenServer.call(:my_server2, :pop) == 3
+    assert GenServer.call(:my_server, :pop) == 1
+  end
+end