undefined | Better HN

0 pointskbd6y ago0 comments

For one meaning of "test", sort of, but repls are useful for far more than "do outputs match what I expect". Test writing is not very good for exploratory programming.

0 comments

marcrosoft6y ago

Tests are perfect for "do outputs match what I expect". If you don't know what you are expecting yet just to `t.Error("")`. When you are done fiddling around and want to solidify what you expect add the `if foo != expectation`.

jpittis6y ago

To add to this, editor commands to quickly switch to your test file, auto generate test boilerplate and run the currently highlighted test are super helpful to speed up this loop.

wc-6y ago

This sounds really helpful, can you provide any links to read more about setting these helpers up?

1 more reply

sreque6y ago

I disagree with this to some extent. Unit tests are a pretty good poor-mans REPL in languages that don't have REPLs. For instance, I've seen people write fake unit tests to do things like query a database for analysis purposes; it was just the fastest way they could come up with to do the exploratory work. What makes a unit test a good poor-mans REPL in a language like java with an IDE is:

* Java IDEs, especially eclipse, are amazing at fast, incremental compilation. You make one change, and then only recompile what you need to.

* Java has no relatively expensive link stage like C++, C, even C# to a lesser extent, when running tests from an IDE. Your IDE can run your unit tests and also be smart enough to only load the classes it needs to run the test.

Most dynamic languages already have a REPL, so the technique of using unit tests for exploratory work isn't necessary, but I think it's very useful for Java at least.

stcredzero6y ago

Unit tests are a pretty good poor-mans REPL in languages that don't have REPLs.

Java IDEs, especially eclipse, are amazing at fast, incremental compilation. You make one change, and then only recompile what you need to.

I always found this lugubrious compared to the experience in many Smalltalks. The Java vs. Smalltalk USENET flame wars in the 90's were partly motivated by the downgrade in developer UX caused by the taking of the Smalltalk runtime model and deliberately crippling it.

Granted, Java has made amazing progress since then, as have IDEs generally. Is there a non-Smalltalk environment that lets one "code in the debugger" to the same extent as Smalltalk? I know of Clojure and the kind of experience shown with LightTable. (To elaborate, to "code in the debugger" in Smalltalk is very nimble and powerful. It's kind of like the turn-based version of LightTable but with pausing in the debugger and manual tinkering/time-travel with the context stack.)

sreque6y ago

The JVM is less dynamic in its ability to reload code, but the payoff is that java code can be 10-100x faster than smalltalk code. I personally think the performance gain is worth it. Hotspot has some limited support for hot code reloading, which is a pre-requisite to being able to "code in your debugger", but it's limited enough that I don't bother with it. Alternatively, you can code in a dynamic language on the JVM such as JRuby or Clojure and have full support for "coding in the debugger". These languages are also a lot slower than Java.

skybrian6y ago

We are talking Go here, which has a fast compiler. The IDE integration isn't always as good as Java, though.

_ivvf6y ago

Go has a fast compiler but to my knowledge has zero support for incremental compilation. It has to recompile the entire project, transitively with all its dependencies, before you can run your code modification. I haven't code in go, but IMO this does not scale well as projects grow in size.

stcredzero6y ago

I find GoLand to be quite good.

1 more reply

weberc26y ago

This tends to be more important in dynamic languages where "the outputs" are often hilariously far from what is reasonable to expect. At least that's where I find I use a REPL in Python--load in some poorly-documented 3rd party library to see what the return type of a function is (for some given inputs) and what properties are available on that object (since the "type" isn't much good given the aforementioned poor state of the docs). In Go, however, you get all the information you need from the type and godoc.org.

stcredzero6y ago

This tends to be more important in dynamic languages where "the outputs" are often hilariously far from what is reasonable to expect.

Most of my experience with dynamic language programming is far from what you describe above. About the only place where I've encountered the like is with Javascript.

https://archive.org/details/wat_destroyallsoftware

I once experienced "magic" jumps in the debugger in Smalltalk, but that was because of some liberties taken with custom methods implemented in C, or because of missing_method style metaprogramming. (#doesNotUndedrstand: in Smalltalk)

weberc26y ago

This experience is commonplace in Python. Can’t speak so much for other languages.

j / k navigate · click thread line to collapse

0 comments

marcrosoft6y ago

jpittis6y ago

To add to this, editor commands to quickly switch to your test file, auto generate test boilerplate and run the currently highlighted test are super helpful to speed up this loop.

wc-6y ago

This sounds really helpful, can you provide any links to read more about setting these helpers up?

1 more reply

sreque6y ago

* Java IDEs, especially eclipse, are amazing at fast, incremental compilation. You make one change, and then only recompile what you need to.

Most dynamic languages already have a REPL, so the technique of using unit tests for exploratory work isn't necessary, but I think it's very useful for Java at least.

stcredzero6y ago

Unit tests are a pretty good poor-mans REPL in languages that don't have REPLs.

Java IDEs, especially eclipse, are amazing at fast, incremental compilation. You make one change, and then only recompile what you need to.

sreque6y ago

skybrian6y ago

We are talking Go here, which has a fast compiler. The IDE integration isn't always as good as Java, though.

_ivvf6y ago

stcredzero6y ago

I find GoLand to be quite good.

1 more reply

weberc26y ago

stcredzero6y ago

This tends to be more important in dynamic languages where "the outputs" are often hilariously far from what is reasonable to expect.

Most of my experience with dynamic language programming is far from what you describe above. About the only place where I've encountered the like is with Javascript.

https://archive.org/details/wat_destroyallsoftware

weberc26y ago

This experience is commonplace in Python. Can’t speak so much for other languages.

j / k navigate · click thread line to collapse