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Comment by tensor | Hacker News Reader

It addresses similar problems as static typing, yes, but it's not a compile time check. Instead, it's an optional runtime check. The idea is to use it during testing and development, and have it be disabled during production.

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Its also great at validating data!

We're running some of our specs in production to enforce guarantees on data coming in and out of the app :)

Yup, specs can be used at runtime as well. Very helpful to validate data, or perhaps a set of business rules. Insures the spec you use to test is the same logic you use at runtime.

>specs can be used at runtime as well.

What do you mean "as well"? I thought it was only a runtime check at all.

One of the stated goals of spec is generative testing. While technically runtime, it's is not runtime from the user's point of view.

i think they're talking about production run time versus development runtime. think of it as turning asserts off on production builds. but spec can conform data and explain the reason for non-conformance so some might leave some spec in production for logging, messages, etc.

^^ this, using spec at run time in your actual application logic

That's right spec is a runtime thing.

This Spectrum thing purports to evaluate your specs at compile time though:

https://github.com/arohner/spectrum

Macros are checked at compile time. So it is a static check to some extent.

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