test(invariant): add test code

[ssi02014]

The first argument of the invariant function is named condition, and given the use case, it would be nice to define it as a boolean type, what do you think?

Is there a reason why the type is unknown?

I additionally added test code for type narrowing for the invariant function.

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Name	Status	Preview	Comments	Updated (UTC)
es-toolkit	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Nov 9, 2024 3:38pm

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.11%. Comparing base (0feabb4) to head (7c8fa9e).

Additional details and impacted files

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##             main     #789   +/-   ##
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  Coverage   99.11%   99.11%           
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  Files         305      305           
  Lines        2727     2727           
  Branches      800      800           
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  Hits         2703     2703           
  Misses         23       23           
  Partials        1        1           

[raon0211]

Actually it is common practice to write code like if (!number) or if (obj) -- that's the reason why we have unknown here. So I would like to stick with the current code.

[ssi02014]

@raon0211
I understand. The naming of condition can be confusing, but as you said, it is correct to keep the current code to allow different types of values.

1. Have you ever thought about renaming the argument?
2. What do you think of the test code added by this work?

[raon0211]

Yeah, the test code will definitely help. In the meantime, I thought using if (condition) is pretty common in JavaScript, so I figured condition would be a good name. Do you have any thoughts on the name?

[ssi02014]

@raon0211 It would be nice to have a name that encompasses both, since it can take a value as an argument in addition to the usual condition, but unfortunately I don't have a good idea yet. 😭

So, I'm going to keep the existing code and just add the test code.

[ssi02014]

@raon0211 I reverted the existing modifications, leaving only the test code. Thanks for the review. 🤗

[raon0211]

Thanks!