Tests should be aware of the Current Culture Info

Hello,

As i'm French, my CultureInfo.CurrentCulture is set to "fr-FR" while running tests.
But for some tests, especially for the ToString() methods, tests are write to check "en-US" Culture.
Yes sure, I was thinking about that in my way to home !
I will rewrite this tests using the string.format, the responsability for the number formatting should not be here.