-shouldBe('stepUp("2010-W02", null, null, "0")', '"2010-W02"');
-shouldBe('stepDown("2010-W02", null, null, "0")', '"2010-W02"');
-shouldBe('stepUp("2010-W02", null, null, "foo")', '"2010-W02"');
-shouldBe('stepDown("2010-W02", null, null, "foo")', '"2010-W02"');
-shouldBe('stepUp("2010-W02", null, null, null)', '"2010-W02"');
-shouldBe('stepDown("2010-W02", null, null, null)', '"2010-W02"');
+shouldBeEqualToString('stepUp("2010-W02", null, null, "0")', '2010-W02');
+shouldBeEqualToString('stepDown("2010-W02", null, null, "0")', '2010-W02');
+shouldBeEqualToString('stepUp("2010-W02", null, null, "foo")', '2010-W02');
+shouldBeEqualToString('stepDown("2010-W02", null, null, "foo")', '2010-W02');
+shouldBeEqualToString('stepUp("2010-W02", null, null, null)', '2010-W02');
+shouldBeEqualToString('stepDown("2010-W02", null, null, null)', '2010-W02');