various small refactorings

test/models/is_taggable_test.rb

@@ -42,5 +42,33 @@ class IsTaggableTest < ActiveSupport::TestCase
     t.tag_with "a, b, e, f"
     assert_equal "a, b, e, f", t.tag_list, "should add e and f and remove c and d"
   end
+
+  def test_editing_using_taglist
+    t = Todo.create(:description => "test", :context => Context.first)
+    t.tag_list = "a, b, c"
+    assert_equal 3, t.tags.count
+    assert_equal "a, b, c", t.tag_list
+
+
+    t.tag_list = "d, e"
+    assert_equal 2, t.tags.count
+    assert_equal "d, e", t.tag_list
+  end
   
+  def test_tag_cast_to_string
+    t = Todo.create(:description => "test", :context => Context.first)
+
+    obj = "tag"
+    assert_equal ["tag"], t.tag_cast_to_string(obj)
+
+    obj = ["tag1", Tag.new(name: "tag2")]
+    assert_equal ["tag1", "tag2"], t.tag_cast_to_string(obj)
+
+    obj = {a: "hash"}
+    assert_raise(RuntimeError) { t.tag_cast_to_string(obj) } 
+
+    obj = ["string", {a: "hash"}]
+    assert_raise(RuntimeError) { t.tag_cast_to_string(obj) } 
+  end
+
 end