[ci skip] make assert messages consistent

activemodel/test/cases/validations_test.rb

@@ -18,11 +18,11 @@ def teardown
   def test_single_field_validation
     r = Reply.new
     r.title = "There's no content!"
-    assert r.invalid?, "A reply without content shouldn't be savable"
+    assert r.invalid?, "A reply without content should be invalid"
     assert r.after_validation_performed, "after_validation callback should be called"
 
     r.content = "Messa content!"
-    assert r.valid?, "A reply with content should be savable"
+    assert r.valid?, "A reply with content should be valid"
     assert r.after_validation_performed, "after_validation callback should be called"
   end