4 ms·

TDD assumes you know what all the interfaces are going to be beforehand. If you discover that an interface needs to change you have to refactor all of your tes

by snarfy 11y ago

TDD assumes you know what all the interfaces are going to be beforehand. If you discover that an interface needs to change you have to refactor all of your tests. Unit tests are momentum against change. It also assumes a bug free app with 100% code coverage is the objective, regardless of the cost it takes to write all that test code. An app that has a few bugs but takes half the resources to develop can make better business sense.

mabbo 11y ago
> It also assumes a bug free app with 100% code coverage is the objective, regardless of the cost it takes to write all that test code. I disagree on this. 100% coverage is actually a bad thing, in my opinion, because there's always a lot of code you do not need to test (simple constructors, accessors/mutators, etc). A unit test should test things that you are relying on being correct. You write a unit test as a way to protect future developers (including yourself) from totally screwing things up by accidentally changing something important. An application with a few bugs that took half the resources to develop is nice- until the customer needs a few extra changes 18 months later, and you turn 'a few' bugs into 'a whole lot of' bugs.
sulami 11y ago
> Unit tests are momentum against change. I get the point, but feel different. When a project becomes large enough, changes can result in breakage in the weirdest places. Proper testing can help discovering this breakage before shipping. For me, tests are a safety net for changes in the tested code. Large projects without any tests are effectively unmaintainable, often times even for the original author, and most certainly for others.
- snarfy 11y ago
  I do agree with this, and have felt it from both ends. If you need to change a core class or interface which cascades throughout the system, those unit tests are sure nice to have. I'm not sure I'd be confident enough to change the core class without the unit tests. In that sense, lack of unit tests is momentum against change.
hhandoko 11y ago
There is no such thing as bug-free app, and I do not agree for 100% code coverage (rather write test for what's important to you, i.e. prioritise). However, tests gives you a higher level of confidence when you perform refactoring. PS. Regression is far worse than momentum against change, when your app is `broken` you can't deliver it.

by snarfy 11y ago

mabbo 11y ago

> It also assumes a bug free app with 100% code coverage is the objective, regardless of the cost it takes to write all that test code. I disagree on this. 100% coverage is actually a bad thing, in my opinion, because there's always a lot of code you do not need to test (simple constructors, accessors/mutators, etc). A unit test should test things that you are relying on being correct. You write a unit test as a way to protect future developers (including yourself) from totally screwing things up by accidentally changing something important. An application with a few bugs that took half the resources to develop is nice- until the customer needs a few extra changes 18 months later, and you turn 'a few' bugs into 'a whole lot of' bugs.

sulami 11y ago

> Unit tests are momentum against change. I get the point, but feel different. When a project becomes large enough, changes can result in breakage in the weirdest places. Proper testing can help discovering this breakage before shipping. For me, tests are a safety net for changes in the tested code. Large projects without any tests are effectively unmaintainable, often times even for the original author, and most certainly for others.

snarfy 11y ago
I do agree with this, and have felt it from both ends. If you need to change a core class or interface which cascades throughout the system, those unit tests are sure nice to have. I'm not sure I'd be confident enough to change the core class without the unit tests. In that sense, lack of unit tests is momentum against change.

hhandoko 11y ago

There is no such thing as bug-free app, and I do not agree for 100% code coverage (rather write test for what's important to you, i.e. prioritise). However, tests gives you a higher level of confidence when you perform refactoring. PS. Regression is far worse than momentum against change, when your app is `broken` you can't deliver it.