Refactor Koan with slow/fast process example

A combined solution of the examples provided by
@iamvery and myself.

lib/koans/15_processes.ex

@@ -17,21 +17,23 @@ defmodule Processes do
     assert is_pid(self()) == ___
   end
 
-  koan "Like our current process, new processes are spawned functions" do
+  koan "New processes are spawned functions" do
-    pid = spawn(fn -> nil end)
+    value = spawn(fn -> nil end)
 
-    assert is_pid(pid) == ___
+    assert is_pid(value) == ___
   end
 
-  koan "Processes exit after executing their function, unless they wait for something" do
+  koan "Processes die when their function exits" do
-    wait_forever = fn ->
+    fast_process = spawn(fn -> :timer.sleep(10) end)
-      receive do
+    slow_process = spawn(fn -> :timer.sleep(1000) end)
-      end
-    end
 
-    pid = spawn(wait_forever)
+    # All spawned functions are executed concurrently with the current process.
+    # You check back on slow_process and fast_process 50ms later. Let's
+    # see if they are still alive!
+    :timer.sleep(50)
 
-    assert Process.alive?(pid) == ___
+    assert Process.alive?(fast_process) == ___
+    assert Process.alive?(slow_process) == ___
   end
 
   koan "Processes can send and receive messages" do
@@ -42,6 +44,17 @@ defmodule Processes do
     end
   end
 
+  koan "A process will wait forever for a message" do
+    wait_forever = fn ->
+      receive do
+      end
+    end
+
+    pid = spawn(wait_forever)
+
+    assert Process.alive?(pid) == ___
+  end
+
   koan "Received messages are queued, first in first out" do
     send self(), "hola!"
     send self(), "como se llama?"

test/koans/processes_koans_test.exs

@@ -8,8 +8,9 @@ defmodule ProcessesTests do
       :running,
       true,
       true,
-      true,
+      {:multiple, [false, true]},
       "hola!",
+      true,
       {:multiple, ["hola!", "como se llama?"]},
       :how_are_you?,
       {:multiple, ["O", "HAI"]},