How is it NOT a religious test?
If someone is being denied the ability to remain in the employ of the federal government based solely on whether or not they choose to include "so help me God" in an oath, how can this NOT be construed as being a 'religious test'? I suspect that the courts will agree with me on this one. Besides, I'm sure that there are dozens, if no hundreds, of other 'federal employees' who have not been 'let go' for exercising their rights to skip the aforementioned passage so this would provide many precedents which could be sited by counsel.
BTW, were you aware that even the use of the words 'swearing an oath' has religious overtones, which is why the Constitutions clearly allows that a person may either 'swear' or 'affirm' their intentions when taking office? This was included in the Constitution at the specific request of the Quakers for whom 'swearing an oath' was to violate scripture as stated in James 5:12. Other Christians believe this as well. Even Catholics were taught years ago that they could not be a member of any organization which required that they "swear an oath" before they were allowed to join.

OCU