Add exercises 4 and 5 from chapter 14

Author: Bernard Pietraga

chapter_14/working_with_multiple_processes_4.exs

@@ -0,0 +1,47 @@
+defmodule Linker2 do
+  import :timer, only: [sleep: 1]
+
+  def notify(sender) do
+    send sender, "Hello Kermit!"
+    raise RuntimeError, message: "Child raised error"
+  end
+
+  def read_message do
+    receive do
+      msg ->
+        IO.puts "MESSAGE RECIEVED #{inspect msg}"
+        read_message()
+    after 0 ->
+        IO.puts "No more messages in mailbox"
+    end
+  end
+
+  def run do
+    Process.flag(:trap_exit, true)
+    spawn_link(Linker2, :notify, [self()])
+    :timer.sleep(500)
+    read_message()
+  end
+end
+
+
+ExUnit.start
+
+defmodule Linker2Test do
+  use ExUnit.Case
+  import ExUnit.CaptureIO
+
+  test "run returns proper messages" do
+    messages_string = """
+    MESSAGE RECIEVED \"Hello Kermit!\"
+    MESSAGE RECIEVED {:EXIT, #PID<0.95.0>, {%RuntimeError{message: \"Child raised error\"}, [{Linker2, :notify, 1, [file: 'working_with_multiple_processes_4.exs', line: 6]}]}}
+    No more messages in mailbox
+    """
+
+    expected = capture_io fn ->
+      Linker2.run
+    end
+
+    assert expected == messages_string
+  end
+end

chapter_14/working_with_multiple_processes_5_a.exs

@@ -0,0 +1,48 @@
+defmodule Linker3 do
+  import :timer, only: [sleep: 1]
+
+  def notify(sender) do
+    send sender, "Hello Kermit!"
+    exit(:boom)
+  end
+
+  def read_message do
+    receive do
+      msg ->
+        IO.puts "MESSAGE RECIEVED #{inspect msg}"
+        read_message()
+    after 0 ->
+        IO.puts "No more messages in mailbox"
+    end
+  end
+
+  def run do
+    Process.flag(:trap_exit, true)
+    spawn_monitor(Linker3, :notify, [self()])
+    :timer.sleep(500)
+    read_message()
+  end
+end
+
+
+ExUnit.start
+
+defmodule Linker3Test do
+  use ExUnit.Case
+  import ExUnit.CaptureIO
+
+  test "run returns proper messages" do
+    # Use regex as dynamicaly reference changes
+    {:ok, regex_1} = Regex.compile("MESSAGE RECIEVED \"Hello Kermit!\"")
+    {:ok, regex_2} = Regex.compile("MESSAGE RECIEVED {:DOWN, ")
+    {:ok, regex_3} = Regex.compile("No more messages in mailbox")
+
+    expected = capture_io fn ->
+      Linker3.run
+    end
+
+    assert Regex.match?(regex_1, expected)
+    assert Regex.match?(regex_2, expected)
+    assert Regex.match?(regex_3, expected)
+  end
+end

chapter_14/working_with_multiple_processes_5_b.exs

@@ -0,0 +1,58 @@
+
+defmodule Linker4 do
+  import :timer, only: [sleep: 1]
+
+  def notify(sender) do
+    send sender, "Hello Kermit!"
+    raise RuntimeError, message: "Child raised error"
+  end
+
+  def read_message do
+    receive do
+      msg ->
+        IO.puts "MESSAGE RECIEVED #{inspect msg}"
+        read_message()
+    after 0 ->
+        IO.puts "No more messages in mailbox"
+    end
+  end
+
+  def run do
+    Process.flag(:trap_exit, true)
+    spawn_monitor(Linker4, :notify, [self()])
+    :timer.sleep(500)
+    read_message()
+  end
+end
+
+
+ExUnit.start
+
+defmodule Linker4Test do
+  use ExUnit.Case
+  import ExUnit.CaptureIO
+
+  test "run returns proper messages" do
+    {:ok, regex_1} = Regex.compile("MESSAGE RECIEVED \"Hello Kermit!\"")
+    {:ok, regex_2} = Regex.compile("MESSAGE RECIEVED {:DOWN, ")
+    {:ok, regex_3} = Regex.compile("{%RuntimeError{message: ")
+    {:ok, regex_4} = Regex.compile("\"Child raised error\"}, ")
+    {:ok, regex_5} = Regex.compile("Linker4, :notify, 1")
+    {:ok, regex_6} = Regex.compile("file: 'working_with_multiple_processes_5_b.exs',")
+
+    messages_string = """
+    No more messages in mailbox
+    """
+
+    expected = capture_io fn ->
+      Linker4.run
+    end
+
+    assert Regex.match?(regex_1, expected)
+    assert Regex.match?(regex_2, expected)
+    assert Regex.match?(regex_3, expected)
+    assert Regex.match?(regex_4, expected)
+    assert Regex.match?(regex_5, expected)
+    assert Regex.match?(regex_6, expected)
+  end
+end