Add keyword arguments (with correct answers).

src/about_keyword_arguments.rb

@@ -0,0 +1,31 @@
+require File.expand_path(File.dirname(__FILE__) + '/edgecase')
+
+class AboutMethods < EdgeCase::Koan
+
+  def method_with_keyword_arguments(one: 1, two: 'two')
+    [one, two]
+  end
+
+  def test_keyword_arguments
+    assert_equal __(Array), method_with_keyword_arguments.class
+    assert_equal __([1, 'two']), method_with_keyword_arguments
+    assert_equal __(['one', 'two']), method_with_keyword_arguments(one: 'one')
+    assert_equal __([1, 2]), method_with_keyword_arguments(two: 2)
+  end
+
+  def method_with_keywork_arguments_with_mandatory_argument(one, two: 2, three: 3)
+    [one, two, three]
+  end
+
+  def test_keyword_arguments_with_wrong_number_of_arguments
+    exception = assert_raise (___(ArgumentError)) do
+      method_with_keywork_arguments_with_mandatory_argument
+    end
+    assert_match(/#{__("wrong number of arguments")}/, exception.message)
+  end
+
+  # THINK ABOUT IT:
+  #
+  # Keyword arguments always have a default value, making them optional to the caller
+
+end