Testing a model on a tree with a single tip

[Boussau]

Hi, I'd like to test a substitution matrix on a single branch through the rev language. Has anybody successfully done that before? For a tree with one taxon, I seem to have difficulties to use the dnBDP, or similar distributions for branch-lengh trees, or to read a tree with a single branch into RevBayes.
In that latter case it seems it reads the name incorrectly: after reading a tree file containing:
(t1:1.0);
I get
print(startingTree.names())
,t1
The comma worries me, and when I use dnPhyloCTMC with that tree and a sequence file, I get
Error: Ambiguous taxon name.
Any other idea of what I should use?
Thanks!