You shouldn't be hearing "test" as part of the exchange. Part of a "CQ" maybe. That said...
The classic CW shortcut for 599 is 5nn but sometimes speed demons shorten that to "snn"
Further, there's the use of "cut" numbers for the zone - like a "T" for a zero - which is very common.
So...maybe you heard "T4" for (zone) "04" ? Was it a statesider giving the exchange?
Since it appears you might not know much about CW shorthand (ie cut numbers), some other cut numbers commonly used:
Cut # = Actual Meaning
A = 1
T = 0
N = 9
K = 1000 (in the case of power levels as part of the exchange - however not used in the CQWW CW test)
so a commonly seen exchange in the CQW CW contest might be '5nn t3 t3' which is 5 9 9 (standard contest RST) followed by '03 03' which would be Zone 3 (western US/Canada). Much quicker to send 'T' than 'Ø'.
Also as mentioned, 'TEST' is just a shorthand for 'CONTEST' and is easy to hear I think. My ears listen for TEST rather then CONtest. In fact my ringtone on my cellphone is 20WPM "CQ TEST W5DQ" which I can hear in a noisy environment much better any other ringtone I've tried.