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As someone who spent a good chunk of their career teaching TDD, I agree and disagree. Yes, tests are crucial. However, which tests to write varies among other t

As someone who spent a good chunk of their career teaching TDD, I agree and disagree. Yes, tests are crucial. However, which tests to write varies among other things by language. When I write Ruby, I benefit from testing even the simplest things. When I write Rust or even Type Script or Swift I'll focus much more on tests for complex logic and on integration and acceptance tests. Static typing eliminates an entire, larger category of issue I need to address with tests.

pantulis 4y ago
Sure! But you need to be a testing practitioner anyway. I agree that perhaps the number of tests is different, but the teams processes and cultures should already be there. But to counter myself, the perceived lack of developer speed and flexiblity of a strongly typed language (with Rust, I always get the feeling that I'm fighting with the compiler!) is also solved in the long run with practice and tooling.
vidarh 4y ago
When I write Ruby, I test expected behaviours, and if there are type errors in there those tends to fall out from tests I needed anyway. If you need to test specifically for errors due types, then generally that suggests that either your application does not normally exercise those code paths at all and/or you fail to test behaviours of your application.
- Yoric 4y ago
  Does this include writing libraries for use by third-parties?
  - vidarh 4y ago
    To an extent. In libraries for third parties you do need to test contracts specified by your docs, but a well written Ruby library should intentionally avoid over-testing typing (both in separate tests and in code) and focus on testing behaviours. Sure, test for sane failure modes in line with the documented contract, and that may include the occasional test that is de facto a type test, but often testing for types, especially in languages with poor type systems, but also in Ruby where we have alternatives, ends up with tests for classes which is frequently the wrong thing. E.g. in Ruby never, ever check for somearg.kind_of?(IO) if all you ever do is somearg.read - if you absolutely must typecheck somearg, the Ruby way is to check for presence of "#read", e.g. somearg.respond_to?(:read), or try and fail responsibly (and often just allowing the NoMethodError to bubble up is the right way to fail). Also think it's just fine for people to add and ship Sorbet type declarations for gems etc. to then signal those contracts so people can verify them if they choose. There's no reason not to offer that when it's reasonable to do so.
    - Yoric 4y ago
      I have zero to no experience coding in Ruby, so I cannot comment in that case. In Python or JavaScript/TypeScript, though, my experience is that failing to validate types at the borders (i.e. every single function/method/constructor/generator/... exposed in your API) is pretty much guaranteed to end up, months later, with developers attempting to sherlock out surprising breakages in production from logs that make no sense and traces that do not show anything remotely close to the actual culprit. I have the scars to show it :) Of course, YMMV.
      - vidarh 4y ago
        The "Ruby way" in this respect tends to be to avoid being over-prescriptive. That doesn't mean "do no checks", but "do only the checks actually needed" with a very different expectation of "what is needed" than in many other languages. Hence don't check for an IO object when what you care about is the presence of a "#read" method. Or don't check if something is an Array if what matters is that it supports "#map". Instead, either somearg.respond_to?(:map), or if it needs more than map, somearg.respond_to?(Enumerable) (this seems broad, but supporting Enumerable only requires implementing "#each" and including the module, so a caller "worst case" can reopen a class or wrap their object), or call one of Array(somearg) (tries "#to_ary" then "#to_a" then falls back to returning [somearg]) or Array.try_convert(somearg) (tries "#to_ary" then falls back on nil). Consistently picking the most generic applicable options when faced with choices like that still enforces the contract on the boundary, but also tends to lead to code with much less ceremony. E.g. far fewer [something]Adapter classes, or glue code to convert data before calling methods that are being overly prescriptive. But for most statically typed languages, when people talk about static typing, they still talk about a class and a type as interchangeable (there are exceptions, and it's getting better, and with increased type inference coupled with increased support for type annotations and analysis of dynamic languages, I expect there to be an increasing convergence, though).
        Yoric 4y ago
        This makes sense, although there are downsides to not naming types, as these serve as documentation. Python documentation has a strong tendency to using descriptions to avoid giving names to types, which imho makes the documentation needlessly confusing. Note that I'm writing "types" and not "classes". Interfaces do just as well, if not better! For what it's worth, in the static realm, OCaml introduce features that let code check for presence of a method (instead of implementing an interface) ~25 years ago. Unfortunately, this proved rather unwieldy and, to the best of my knowledge, nobody uses that feature.
- ajmurmann 4y ago
  100% on testing behavior. That said, I still end up writing more and lower-level tests in Ruby to get fast feedback on silly errors, both in terms of locality of the failing test and in terms of not executing the entire stack to test variations of behavior somewhere deep inside.

pantulis 4y ago

Sure! But you need to be a testing practitioner anyway. I agree that perhaps the number of tests is different, but the teams processes and cultures should already be there. But to counter myself, the perceived lack of developer speed and flexiblity of a strongly typed language (with Rust, I always get the feeling that I'm fighting with the compiler!) is also solved in the long run with practice and tooling.

vidarh 4y ago

When I write Ruby, I test expected behaviours, and if there are type errors in there those tends to fall out from tests I needed anyway. If you need to test specifically for errors due types, then generally that suggests that either your application does not normally exercise those code paths at all and/or you fail to test behaviours of your application.

Yoric 4y ago
Does this include writing libraries for use by third-parties?
- vidarh 4y ago
  To an extent. In libraries for third parties you do need to test contracts specified by your docs, but a well written Ruby library should intentionally avoid over-testing typing (both in separate tests and in code) and focus on testing behaviours. Sure, test for sane failure modes in line with the documented contract, and that may include the occasional test that is de facto a type test, but often testing for types, especially in languages with poor type systems, but also in Ruby where we have alternatives, ends up with tests for classes which is frequently the wrong thing. E.g. in Ruby never, ever check for somearg.kind_of?(IO) if all you ever do is somearg.read - if you absolutely must typecheck somearg, the Ruby way is to check for presence of "#read", e.g. somearg.respond_to?(:read), or try and fail responsibly (and often just allowing the NoMethodError to bubble up is the right way to fail). Also think it's just fine for people to add and ship Sorbet type declarations for gems etc. to then signal those contracts so people can verify them if they choose. There's no reason not to offer that when it's reasonable to do so.
  - Yoric 4y ago
    I have zero to no experience coding in Ruby, so I cannot comment in that case. In Python or JavaScript/TypeScript, though, my experience is that failing to validate types at the borders (i.e. every single function/method/constructor/generator/... exposed in your API) is pretty much guaranteed to end up, months later, with developers attempting to sherlock out surprising breakages in production from logs that make no sense and traces that do not show anything remotely close to the actual culprit. I have the scars to show it :) Of course, YMMV.
    - vidarh 4y ago
      The "Ruby way" in this respect tends to be to avoid being over-prescriptive. That doesn't mean "do no checks", but "do only the checks actually needed" with a very different expectation of "what is needed" than in many other languages. Hence don't check for an IO object when what you care about is the presence of a "#read" method. Or don't check if something is an Array if what matters is that it supports "#map". Instead, either somearg.respond_to?(:map), or if it needs more than map, somearg.respond_to?(Enumerable) (this seems broad, but supporting Enumerable only requires implementing "#each" and including the module, so a caller "worst case" can reopen a class or wrap their object), or call one of Array(somearg) (tries "#to_ary" then "#to_a" then falls back to returning [somearg]) or Array.try_convert(somearg) (tries "#to_ary" then falls back on nil). Consistently picking the most generic applicable options when faced with choices like that still enforces the contract on the boundary, but also tends to lead to code with much less ceremony. E.g. far fewer [something]Adapter classes, or glue code to convert data before calling methods that are being overly prescriptive. But for most statically typed languages, when people talk about static typing, they still talk about a class and a type as interchangeable (there are exceptions, and it's getting better, and with increased type inference coupled with increased support for type annotations and analysis of dynamic languages, I expect there to be an increasing convergence, though).
      - Yoric 4y ago
        This makes sense, although there are downsides to not naming types, as these serve as documentation. Python documentation has a strong tendency to using descriptions to avoid giving names to types, which imho makes the documentation needlessly confusing. Note that I'm writing "types" and not "classes". Interfaces do just as well, if not better! For what it's worth, in the static realm, OCaml introduce features that let code check for presence of a method (instead of implementing an interface) ~25 years ago. Unfortunately, this proved rather unwieldy and, to the best of my knowledge, nobody uses that feature.
ajmurmann 4y ago
100% on testing behavior. That said, I still end up writing more and lower-level tests in Ruby to get fast feedback on silly errors, both in terms of locality of the failing test and in terms of not executing the entire stack to test variations of behavior somewhere deep inside.