I've joined several projects in their maintenance phase which had no tests, and introduced some as I went about debugging, adding features, etc. Since the code was often untestable, I'd make a few refactorings over and over again to allow testing, and these just-so-happen to tease apart the pure computation from the effects; in essence making the code more functional.
An obvious example is to turn implicit state into explicit parameters, eg.
// BEFORE
function foo(x, y) {
b = x + y + a;
}
// AFTER
function foo(x, y) {
b = foo_pure(x, y, a);
}
function foo_pure(x, y, z) {
return x + y + z;
}
This doesn't make `foo` more functional or easier to test; but testing `foo_pure` is trivial. In particular this makes debugging logic errors much easier; since there's no need for elaborate/brittle test setup (eg. setting all the right globals, creating and cleaning up files, etc.).
I've joined several projects in their maintenance phase which had no tests, and introduced some as I went about debugging, adding features, etc. Since the code was often untestable, I'd make a few refactorings over and over again to allow testing, and these just-so-happen to tease apart the pure computation from the effects; in essence making the code more functional.
An obvious example is to turn implicit state into explicit parameters, eg.
This doesn't make `foo` more functional or easier to test; but testing `foo_pure` is trivial. In particular this makes debugging logic errors much easier; since there's no need for elaborate/brittle test setup (eg. setting all the right globals, creating and cleaning up files, etc.).