What should I name this helper class? [closed]

Question

Usually when writing unit tests I create a helper class with extension methods. I use these methods exclusively for generating generic data for things that I am too lazy to type out. I usually name these classes something relevant to the class under test - for example, I'll follow a pattern like TestHelper.cs.

I've read that helper classes don't promote good design; however I know SOLID principles pretty well and I don't see how using "helpers" in the way described is violating any principles.

I think the issue I'm having is with the name of my "TestHelper" ... Should I simply come up with a new naming scheme or am I really violating a SOLID Principle by utilizing these helpers?