On Oct 8, 2012, at 2:04 PM, Brendan Eich wrote: > Allen Wirfs-Brock wrote: >> BTW, an issue that I have seen in some ES test is an implicit assumption >> that the implementation factoring and abstraction layering necessarily >> follows that used by the specification. Just because the spec. uses >> procedural abstraction to define some functionality doesn't mean that the >> functionality can be verify by exercising only one of multiple features that >> depend upon it. > > Indeed, such internal details should not be observable -- so were those tests > counting on leaky abstractions in certain implementation(s)?
For example, assuming that ToNumber of an object calls valueOf can be verified by just writing a test using prefix + and not testing that use case for any other operators. The problem isn't not so much that ToNumber is a leaky abstraction. It's the assumption that implementations will actually implement it as a call to a common procedure. If can get away with such assumptions if you are doing white box testing, but not for black box tested based upon a specification. Allen _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
