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The process goes more like this: 1. Write some code 2. Test it 3. Debug your code 4. Test it 5. Debug your code 6. Test it ... 39. Debug your code 40.

The process goes more like this: 1. Write some code 2. Test it 3. Debug your code 4. Test it 5. Debug your code 6. Test it ... 39. Debug your code 40. Test it; now it finally seems to work If all your "test it" steps are being done manually, you're being very inefficient. A good unit test can actually make development go by faster with the added bonus of defending your code from changes down the road that might screw things up.

niccl 15y ago
That's all fine unless you're exploring a solution space. Then the overhead of writing tests which are thrown away _in entirety_ is outrageous. AFAIK TDD really only works if you're either a) prepared to waste a huge amount of time writing tests which will later be completely redundant or b) working to a very clear set of requirements with tools and frameworks you already know intimately. </Rant>
- pimeys 15y ago
  Of course you have to know your tools. I usually start by doing test cases, then writing the real features while spork and whatchr evaluates my new code every time I save. I rarely even open a browser, it's the final thing I do when my tests are green. It doesn't slow me down, and I can be sure that my feature is there and works even when somebody refactors our software.
- sfev 15y ago
  Sure, but what you're describing is prototyping. Prototype all you want without tests, but once you've settled on a design & are ready to make it production-ready you should spend time at least writing unit tests for your work or (ideally) take what you've learned & re-apply to a clean design written in a test-first manner. You might think this is a waste of time, but putting code into production without tests is going to give you more trouble in the long run.
- viscanti 15y ago
  I find I spend significantly more time refactoring/maintaining code than I spend writing exploratory code. It's silly to write tests for prototype work, but once you're actually close to having a working prototype, tests help. Having decent test coverage saves so much more time when refactoring/maintaining. TDD isn't "THE" way, but test coverage helps. It's not fun (at least not for me), but it's less aggravating than breaking something 6 months down the road in some non-obvious way. I'm human, so I assume I'll screw something up eventually. Having test coverage helps keep me from shooting myself in the foot later.
- mattbriggs 15y ago
  in TDD what you are talking about is called a "spike", just write a bunch of code to try out assumptions and find a direction to go that you are reasonably sure is a good one.
- peeters 15y ago
  Different levels of tests work here. I usually start with a very high-level test and then as I implement I do unit tests once I have a reasonably high confidence that the units are a good design. You should often be able to at least create an automated acceptance test for what you're doing (e.g., "as a user I want to click this button and see XYZ"). This is usually extremely decoupled from the implementation so it should survive refactoring. So then do your exploratory code, get the test passing, and then refactor, introducing lower-level tests. If that doesn't seem doable you might be taking on a task that doesn't have a good set of requirements. Writing code without any concrete use case in mind is fun and all but that kind of code should usually be limited to a prototyping sandbox.
  - colomon 15y ago
    "If that doesn't seem doable you might be taking on a task that doesn't have a good set of requirements." Or it might have perfectly good requirements which are very hard to write automated tests for. Consider (for instance) a program to translate ABC music format to proper sheet music. It's easy to say the basic requirement: "The program has to accurately translate ABC format to legible and easy to read sheet music." But even a start at automating a test for that would require converting a graphical representation of sheet music back to the basic notes, and that problem is at least an order of magnitude harder than writing the original program, without factoring in the "easy to read" bit at all. (PS This is a real issue for me, if someone knows of a decent open source sheet music to MIDI/ABC convertor I'd love to hear about it.)
    - tomgallard 15y ago
      The mistake here is that what you're describing is a functional test, not a unit test. A unit test for a piece of code like this might be "Given that the time signature for the music is 3:4, the software puts 3:4 in the appropriate place on each line of output". You then might write a variety of cases testing that it deals correctly with (say) a changing time signature at some point in the piece. The upside of this is when you try and fix another bug which has a knock on effect on this bit of code, lots of your tests are going to fail- immediately identifying where the problem is (or at least letting you know there is one!)
Retric 15y ago
That's mostly a beginners problem, I know several people where it's mostly: 1. Write a lot of code 2. Test it 3. It works! 4. Test it 5. It works! 6. Test it 7. It works! ... 15. Test it 16. It works! 17. Are you done? TDD in no way makes 17 any clear, because every test they thought of before writing the code works more or less the first time. And that's the core problem with testing, for a solid developer what fails is has nothing to do with the code it's always a question of edge cases they did not think. (Wait, some sales people are their own managers and outside consultants at the same time? well just bob) You can force these people to write tests, but it really does just slow them down.
- mattbriggs 15y ago
  I have never seen any half way decent developer write code for more then a few minutes without some sort of feedback, automated test suite or not. You are right that it will work more or less, but they work out the "less" part of that statement sooner rather then later. In my experience, that is a place you get to over time, only the people out of college write code for multiple hours straight, then debug everything afterwards. That is actually the primary goal of tdd, to free you from the more mundane aspects of the code/run/debug loop. The secondary goal is to give you a good base for changing the code later and finding out what broke, again without a ton of manual actions. But as useful as that is (and it is extremely useful), it doesn't hold a candle to the first benefit.
  - fragsworth 15y ago
    That's the point I was trying to make. The main benefit comes from eliminating the "run/debug" part of the "code/run/debug" loop. It then just becomes "code/test" where "test" takes all of a couple seconds each time.
    - alextgordon 15y ago
      But if you don't run it yourself, how do you know it's working? All you know is that the tests pass. Tests can easily do more harm than good if you let them give you a false sense of security.

niccl 15y ago

That's all fine unless you're exploring a solution space. Then the overhead of writing tests which are thrown away _in entirety_ is outrageous. AFAIK TDD really only works if you're either a) prepared to waste a huge amount of time writing tests which will later be completely redundant or b) working to a very clear set of requirements with tools and frameworks you already know intimately. </Rant>

pimeys 15y ago
Of course you have to know your tools. I usually start by doing test cases, then writing the real features while spork and whatchr evaluates my new code every time I save. I rarely even open a browser, it's the final thing I do when my tests are green. It doesn't slow me down, and I can be sure that my feature is there and works even when somebody refactors our software.
sfev 15y ago
Sure, but what you're describing is prototyping. Prototype all you want without tests, but once you've settled on a design & are ready to make it production-ready you should spend time at least writing unit tests for your work or (ideally) take what you've learned & re-apply to a clean design written in a test-first manner. You might think this is a waste of time, but putting code into production without tests is going to give you more trouble in the long run.
viscanti 15y ago
I find I spend significantly more time refactoring/maintaining code than I spend writing exploratory code. It's silly to write tests for prototype work, but once you're actually close to having a working prototype, tests help. Having decent test coverage saves so much more time when refactoring/maintaining. TDD isn't "THE" way, but test coverage helps. It's not fun (at least not for me), but it's less aggravating than breaking something 6 months down the road in some non-obvious way. I'm human, so I assume I'll screw something up eventually. Having test coverage helps keep me from shooting myself in the foot later.
mattbriggs 15y ago
in TDD what you are talking about is called a "spike", just write a bunch of code to try out assumptions and find a direction to go that you are reasonably sure is a good one.
peeters 15y ago
Different levels of tests work here. I usually start with a very high-level test and then as I implement I do unit tests once I have a reasonably high confidence that the units are a good design. You should often be able to at least create an automated acceptance test for what you're doing (e.g., "as a user I want to click this button and see XYZ"). This is usually extremely decoupled from the implementation so it should survive refactoring. So then do your exploratory code, get the test passing, and then refactor, introducing lower-level tests. If that doesn't seem doable you might be taking on a task that doesn't have a good set of requirements. Writing code without any concrete use case in mind is fun and all but that kind of code should usually be limited to a prototyping sandbox.
- colomon 15y ago
  "If that doesn't seem doable you might be taking on a task that doesn't have a good set of requirements." Or it might have perfectly good requirements which are very hard to write automated tests for. Consider (for instance) a program to translate ABC music format to proper sheet music. It's easy to say the basic requirement: "The program has to accurately translate ABC format to legible and easy to read sheet music." But even a start at automating a test for that would require converting a graphical representation of sheet music back to the basic notes, and that problem is at least an order of magnitude harder than writing the original program, without factoring in the "easy to read" bit at all. (PS This is a real issue for me, if someone knows of a decent open source sheet music to MIDI/ABC convertor I'd love to hear about it.)
  - tomgallard 15y ago
    The mistake here is that what you're describing is a functional test, not a unit test. A unit test for a piece of code like this might be "Given that the time signature for the music is 3:4, the software puts 3:4 in the appropriate place on each line of output". You then might write a variety of cases testing that it deals correctly with (say) a changing time signature at some point in the piece. The upside of this is when you try and fix another bug which has a knock on effect on this bit of code, lots of your tests are going to fail- immediately identifying where the problem is (or at least letting you know there is one!)

Retric 15y ago

That's mostly a beginners problem, I know several people where it's mostly: 1. Write a lot of code 2. Test it 3. It works! 4. Test it 5. It works! 6. Test it 7. It works! ... 15. Test it 16. It works! 17. Are you done? TDD in no way makes 17 any clear, because every test they thought of before writing the code works more or less the first time. And that's the core problem with testing, for a solid developer what fails is has nothing to do with the code it's always a question of edge cases they did not think. (Wait, some sales people are their own managers and outside consultants at the same time? well just bob) You can force these people to write tests, but it really does just slow them down.

mattbriggs 15y ago
I have never seen any half way decent developer write code for more then a few minutes without some sort of feedback, automated test suite or not. You are right that it will work more or less, but they work out the "less" part of that statement sooner rather then later. In my experience, that is a place you get to over time, only the people out of college write code for multiple hours straight, then debug everything afterwards. That is actually the primary goal of tdd, to free you from the more mundane aspects of the code/run/debug loop. The secondary goal is to give you a good base for changing the code later and finding out what broke, again without a ton of manual actions. But as useful as that is (and it is extremely useful), it doesn't hold a candle to the first benefit.
- fragsworth 15y ago
  That's the point I was trying to make. The main benefit comes from eliminating the "run/debug" part of the "code/run/debug" loop. It then just becomes "code/test" where "test" takes all of a couple seconds each time.
  - alextgordon 15y ago
    But if you don't run it yourself, how do you know it's working? All you know is that the tests pass. Tests can easily do more harm than good if you let them give you a false sense of security.