Add an agent to keep track of completed koans

test/tracker_test.exs

@@ -0,0 +1,25 @@
+defmodule TrackerTest do
+  use ExUnit.Case
+
+  @sample_modules [SampleKoan, PassingKoan]
+
+  test "can start" do
+    Tracker.start(@sample_modules)
+    assert Tracker.get == %{total: 2, current: 0}
+  end
+
+  test "can be notified of completed koans" do
+    Tracker.start(@sample_modules)
+    Tracker.completed(:"Hi there")
+    assert Tracker.get == %{total: 2, current: 1}
+  end
+
+  test "multiple comletions of the same koan count only once" do
+    Tracker.start(@sample_modules)
+    Tracker.completed(:"Hi there")
+    Tracker.completed(:"Hi there")
+    Tracker.completed(:"Hi there")
+    Tracker.completed(:"Hi there")
+    assert Tracker.get == %{total: 2, current: 1}
+  end
+end