You are talking about, for example testing breakpoints:
1) Start test of breakpoint
2) test environment calls gdb with a test application as target
3) test environment runs "gdb command runner", connects to gdb and sets a breakpoint
4) test environment runs the debugger via "gdb command runner"
5) target runs into breakpoint gdb halts and returns to "gdb command runner"
6) test environment checks the output of "gdb command runner"
So you need a test environment that support the gdb calls (this can probably integrated in the "gdb command runner" program?) . You need a (or multiple) target application that trigger different gdb events (various signals, exceptions, has multiple variables ecc.). I don't think there will be a "easy" way to add tests...
I can see that you have implemented some tests. Are you not satisfied with them?