test: migrate math/base/special/cos to ULP-based testing

[nirmaljb]

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Resolves #{{TODO: add issue number}}.

Description

What is the purpose of this pull request?

This pull request:

• Migrates existing test cases from relative error-based tolerance checks to ULP-based comparisons
• Uses @stdlib/assert/is-almost-same-value for testing

Related Issues

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This pull request has the following related issues:

• #{{TODO: add related issue number}}

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No.

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[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
math/base/special/cos	$\color{green}236/236$ $\color{green}+0.00%$	$\color{green}14/14$ $\color{green}+0.00%$	$\color{green}2/2$ $\color{green}+0.00%$	$\color{green}236/236$ $\color{green}+0.00%$

The above coverage report was generated for the changes in this PR.

[nirmaljb]

/stdlib update-copyright-years

[stdlib-bot]

/stdlib update-copyright-years

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[nirmaljb]

@kgryte I've addressed your reviews and made those changes.

[nirmaljb]

@anandkaranubc I've addressed the changes that you suggested, please take a look.

[kgryte]

LGTM.

@nirmaljb Before opening an RFC, we should also do a migration for a package requiring tolerances greater than 1 ULP. E.g., https://github.com/stdlib-js/stdlib/tree/8b19d00b71edcd61143c31573eab59cfc6936ab4/lib/node_modules/%40stdlib/math/base/special/ellipe.

I am thinking we should also provide a reference PR which is a little less straightforward and requires fiddling with the tolerances a bit.

[nirmaljb]

@kgryte Thank you for the merge. I will search for such functions that require greater than 1 ulp and confirm with you or @anandkaranubc before opening the RFC.

[anandkaranubc]

Completely second what @kgryte mentioned. Also, while making these changes, make sure the ULP difference you use is the smallest possible for that case. This also means that if you can use t.strictEqual(y, expected[i], ...) instead of t.strictEqual(isAlmostSameValue(y, expected[i], ...), ...), it is highly important to do so.

cc: @nirmaljb

[nirmaljb]

@anandkaranubc Wouldn't that mean that I have to use this branch?

if ( y === expected[ i ] ) {
    t.strictEqual( y, expected[ i ], ...);

[kgryte]

@nirmaljb No, he is suggesting that if you don't have to use approximate equality tests, then don't. So if all the test fixtures match the expected results exactly, there is no need to use isAlmostSameValue at all.

[nirmaljb]

Got it! @kgryte