Initial upload

elixir/take-a-number/test/take_a_number_test.exs

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+defmodule TakeANumberTest do
+  use ExUnit.Case
+
+  @tag task_id: 1
+  test "starts a new process" do
+    pid = TakeANumber.start()
+    assert is_pid(pid)
+    assert pid != self()
+    assert pid != TakeANumber.start()
+  end
+
+  @tag task_id: 2
+  test "reports its own state" do
+    pid = TakeANumber.start()
+    send(pid, {:report_state, self()})
+    assert_receive 0
+  end
+
+  @tag task_id: 2
+  test "does not shut down after reporting its own state" do
+    pid = TakeANumber.start()
+    send(pid, {:report_state, self()})
+    assert_receive 0
+
+    send(pid, {:report_state, self()})
+    assert_receive 0
+  end
+
+  @tag task_id: 3
+  test "gives out a number" do
+    pid = TakeANumber.start()
+    send(pid, {:take_a_number, self()})
+    assert_receive 1
+  end
+
+  @tag task_id: 3
+  test "gives out many consecutive numbers" do
+    pid = TakeANumber.start()
+    send(pid, {:take_a_number, self()})
+    assert_receive 1
+
+    send(pid, {:take_a_number, self()})
+    assert_receive 2
+
+    send(pid, {:take_a_number, self()})
+    assert_receive 3
+
+    send(pid, {:report_state, self()})
+    assert_receive 3
+
+    send(pid, {:take_a_number, self()})
+    assert_receive 4
+
+    send(pid, {:take_a_number, self()})
+    assert_receive 5
+
+    send(pid, {:report_state, self()})
+    assert_receive 5
+  end
+
+  @tag task_id: 4
+  test "stops" do
+    pid = TakeANumber.start()
+    assert Process.alive?(pid)
+    send(pid, {:report_state, self()})
+    assert_receive 0
+
+    send(pid, :stop)
+    send(pid, {:report_state, self()})
+    refute_receive 0
+    refute Process.alive?(pid)
+  end
+
+  @tag task_id: 5
+  test "ignores unexpected messages and keeps working" do
+    pid = TakeANumber.start()
+
+    send(pid, :hello?)
+    send(pid, "I want to speak with the manager")
+
+    send(pid, {:take_a_number, self()})
+    assert_receive 1
+
+    send(pid, {:report_state, self()})
+    assert_receive 1
+
+    # This is necessary because `Process.info/1` is not guaranteed to return up-to-date info immediately.
+    dirty_hacky_delay_to_ensure_up_to_date_process_info = 200
+    :timer.sleep(dirty_hacky_delay_to_ensure_up_to_date_process_info)
+
+    # Do not use `Process.info/1` in your own code.
+    # It's meant for debugging purposes only.
+    # We use it here for didactic purposes because there is no alternative that would achieve the same result.
+    assert Keyword.get(Process.info(pid), :message_queue_len) == 0
+  end
+end

elixir/take-a-number/test/test_helper.exs

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+ExUnit.start()
+ExUnit.configure(exclude: :pending, trace: true, seed: 0)