[TASK] Refactor unit test to cover stdWrap_round

- Refactor the origninal test of stdWrap_round to test the method round
  instead.
- Improve that test.
- Add another test to show that stdWrap_round delegates to round.

Releases: master
Resolves: #76774
Change-Id: I406c102efd374269262d8fc6813d0ba7a4bf3f8b
Reviewed-on: https://review.typo3.org/48680


Reviewed-by: Daniel Goerz <ervaude@gmail.com>
Tested-by: Daniel Goerz <ervaude@gmail.com>
Tested-by: Bamboo TYPO3com <info@typo3.com>
Reviewed-by: Susanne Moog <typo3@susannemoog.de>
Tested-by: Susanne Moog <typo3@susannemoog.de>