'''''XpPitfalls'''''

* '''Problem:''' YAGNI can encourage careless or unprofessional coding.

Solution: Don't Be Stupid.



* '''Problem:''' YAGNI seems to conflict with Refactoring.  It can appear that "the simplest thing" is to leave the code alone and move on to the next story.

Solution: RefactoringTrumpsYagni.  It's more important to maintain
code quality (a Developer right) than to increase business value by
adding a feature (a Customer right).  But note also that adding a
feature too early may actually decrease overall velocity, by reducing
code quality, thus reducing business value (or more precisely,
reducing the rate of increase of business value).

The attitude that the Developer's rights trump the Customer's rights almost sounds like its own XP pitfall.  Alternatively stated: It's more important to maintain the customer's right to "change your mind, to substitute functionality, and to change priorities without paying exorbitant costs" (CustomerBillOfRights) than to increase business value by adding a feature.

Solution: Often, refactoring '''before''' implementing a feature -- that
is, sitting down with a new story, and instead of starting with a
test, starting with a refactoring of the areas of code that will need
to be altered -- will actually make it much easier to implement that
feature.

Solution: Realize that YAGNI and Refactoring ARE IN NO WAY
OPPOSED. They never come into conflict, so there is never a need for
one to "trump" the other. They are both implied by Assume Simplicity,
applied at different times relative to the code in question:

* "You Ain't Gonna Need It" says to '''not add''' complexity until you actually need it.
* "Refactor Mercilessly" says to '''remove''' complexity when you realize you don't need it.

I guess the confusion arises when folks assume that refactoring implies
introducing generality, which is not the case. Sometimes refactoring
involves evolving the code from several special cases to one general case;
but if introducing generality makes the code more complex, that ain't
refactoring, and you ain't gonna need it. -JustinSampson

Solution: "Simple" in "the simplest thing" refers to cleanliness of
design, not "minimal changes from whatever I happen to have right
now."  The latter has its place (see thrashing, above), but if taken
too far, everything turns into molasses.  -JimKingdon