Regex Negative look ahead in ADFS claim rule

Question

I need to grant a claim to everyone not matching a particular LDAP attribute. I want to use a regex with a negative look ahead to perform this "not" clause

c1:[Type == "http://schemas.xmlsoap.org/ws/2005/05/identity/claims/name", Value =~ "^(?!Test User).*$"]
 => issue(Type = "http://goofyclaim", Value = "youre not a tester");

the above rule doesn't seem to get satisfied by my test users. Something wrong with the regex? or does ADFS4.0 not support it. I don't see any errors in the ADFS event logs.

this is a win2016srv on a win2012r2 AD domain.

for reference, this rule does work:

c1:[Type == "http://schemas.xmlsoap.org/ws/2005/05/identity/claims/name", Value =~ "(?i)^Test User1"]  
 => issue(Type = "http://somethignelseentreily", Value = "imispellwhendriving");

Answer 1

first I need to use (found here ADFS rules language terminals) for REGEXP_NOT_MATCH

!~

Next, I had to restructure the regex mode modifier a little, by having the case insensitivity inside the ^ idenifier

c1:[Type == "http://schemas.xmlsoap.org/ws/2005/05/identity/claims/name", Value !~ "^(?i)Test User"]
 => issue(Type = "http://somethignelseentreily", Value = "imispellwhendriving");

Answer 2

(leaving my other answer so other can see its not the right answer)

NOT EXISTS([Type == "http://schemas.xmlsoap.org/ws/2005/05/identity/claims/name", Value =~ "^Test User"])
 => issue(Type = "http://somethignelseentreily", Value = "all");