In VBS, with Option Explicit a runtime error is thrown if the interpreter executes a statement containing an undeclared variable.
The shortfall is: this is done at runtime, at execution time. It can take TC very long to get there, just to stop with a runtime error.
TC shall check VBS modules for undeclared/misspelled variable names and inhibit the test run, as it does for syntax errors.
I'm aware that it will probably not be possible to catch all of the typos like this, misspelled members of classes may be impossible to find. But: finding undeclared variables would help.