I live out of consulting, and my biggest projects is writing experimental consumer behavior simulation engines.
Is not that TDD does not have a value, it is just impractical
For once, since they are simulations, they are trying to predict the future, hence there is no right answer, there is the "Acceptable" answer, or the "Defensible" answer; so having a little test on the side that tells me that I am still producing the predicted result does not help much because there is no such thing as the correct predicted result
Sure I can do test to make sure I match the excel spreadsheet that I receive for spec, they would tell me that I copy the formulas correctly; but then, for seconds, I bring the results back and they test it with more real data, and they realize that we need to tweak 100s of different little formulas (which invalidate all the unit tests), change the order of a few of them, and introduced a couple of new ones (as I was told once "because I don't know what I was smoking that Tuesday, so we should use this new one"), and of course "can we have these changes for the end of the day?"
So it all unit tests are voided, make all those changes which are simple enough to be done in a couple of hours. And I am not going to know what is the correct result because there is no valid spreadsheet now, so I don't know in advance what is expected, hence I cannot write the test first
And wait until I try to tell them, the modifications will take 2 hours, but I need another 2 days to write the new set of unit tests, which since I wrote with the result of the modifications instead of before the modifications, they will not prove anything
Rinse and repeat 10s times a month for the last 4 years...
I live out of consulting, and my biggest projects is writing experimental consumer behavior simulation engines.
Is not that TDD does not have a value, it is just impractical
For once, since they are simulations, they are trying to predict the future, hence there is no right answer, there is the "Acceptable" answer, or the "Defensible" answer; so having a little test on the side that tells me that I am still producing the predicted result does not help much because there is no such thing as the correct predicted result
Sure I can do test to make sure I match the excel spreadsheet that I receive for spec, they would tell me that I copy the formulas correctly; but then, for seconds, I bring the results back and they test it with more real data, and they realize that we need to tweak 100s of different little formulas (which invalidate all the unit tests), change the order of a few of them, and introduced a couple of new ones (as I was told once "because I don't know what I was smoking that Tuesday, so we should use this new one"), and of course "can we have these changes for the end of the day?"
So it all unit tests are voided, make all those changes which are simple enough to be done in a couple of hours. And I am not going to know what is the correct result because there is no valid spreadsheet now, so I don't know in advance what is expected, hence I cannot write the test first
And wait until I try to tell them, the modifications will take 2 hours, but I need another 2 days to write the new set of unit tests, which since I wrote with the result of the modifications instead of before the modifications, they will not prove anything
Rinse and repeat 10s times a month for the last 4 years...