Koans about processes including infrastructure.

lib/koans/10_processes.ex

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+defmodule Processes do
+  use Koans
+
+  koan "tests run in a process!" do
+    assert Process.alive?(self)
+  end
+
+  koan "can spew out information about a process" do
+    information = Process.info(self)
+
+    assert information[:status] == :running
+  end
+
+  koan "process can send messages to itself" do
+    send self(), "hola!"
+    receive do
+      message -> assert message == "hola!"
+    end
+  end
+
+  koan "a spawned process is independent of the current process" do
+    pid = spawn(fn -> receive do
+                         {:hello, thing} -> assert thing == "world"
+                         _ -> assert false
+                      end
+                 end)
+
+    send pid, {:hello, "world"}
+  end
+
+  koan "a common pattern is to include the sender in the message" do
+    pid = spawn(fn -> receive do
+                         {:hello, sender} -> send sender, :how_are_you?
+                         _ -> assert false
+                      end
+                 end)
+
+    send pid, {:hello, self()}
+    assert_receive :how_are_you?
+  end
+
+  koan "you don't have to wait forever for messages" do
+    parent = self
+    spawn(fn -> receive do
+                   _ -> assert false
+                after
+                  10 -> send parent, {:waited_too_long, "I am inpatient"}
+                end
+           end)
+
+    assert_receive {:waited_too_long, "I am inpatient"}
+  end
+end