1 files changed, 65 insertions, 0 deletions
diff --git a/test/test_observer.rb b/test/test_observer.rb
new file mode 100644
index 0000000000..e2c159ad09
--- /dev/null
+++ b/test/test_observer.rb
@@ -0,0 +1,65 @@
+require 'test/unit'
+require 'observer'
+
+class TestObserver < Test::Unit::TestCase
+  class TestObservable
+    include Observable
+
+    def notify(*args)
+      changed
+      notify_observers(*args)
+    end
+  end
+
+  class TestWatcher
+    def initialize(observable)
+      @notifications = []
+      observable.add_observer(self)
+    end
+
+    attr_reader :notifications
+
+    def update(*args)
+      @notifications << args
+    end
+  end
+
+  def test_observers
+    observable = TestObservable.new
+
+    assert_equal(0, observable.count_observers)
+
+    watcher1 = TestWatcher.new(observable)
+
+    assert_equal(1, observable.count_observers)
+
+    observable.notify("test", 123)
+
+    watcher2 = TestWatcher.new(observable)
+
+    assert_equal(2, observable.count_observers)
+
+    observable.notify(42)
+
+    assert_equal([["test", 123], [42]], watcher1.notifications)
+    assert_equal([[42]], watcher2.notifications)
+
+    observable.delete_observer(watcher1)
+
+    assert_equal(1, observable.count_observers)
+
+    observable.notify(:cats)
+
+    assert_equal([["test", 123], [42]], watcher1.notifications)
+    assert_equal([[42], [:cats]], watcher2.notifications)
+
+    observable.delete_observers
+
+    assert_equal(0, observable.count_observers)
+
+    observable.notify("nope")
+
+    assert_equal([["test", 123], [42]], watcher1.notifications)
+    assert_equal([[42], [:cats]], watcher2.notifications)
+  end
+end