Cannot use "don't care" character "x" on inputs of the vector test function

Cannot use "don't care" character "x" on inputs of the vector test function

The vector test function on logical gates behaves strangely with "don't care" character "x" on inputs. The documentation says: For hex, octal, and binary values, a digit of 'x' specifies four, three, or one "don't care" bits.

For me this means: x can be either 0 or 1, but the vector testing is using "undefined" at least for one bit inputs. This will give an error signal on output wire of a gate and results in a failing test and is therefor not usable on input ports.

See example with a NAND gate test vector:

Test outcome:

Circuit state:

When using "don't care" character on inputs the vector testing should do tests on all input combination like the function Analyse Circuit does. The results of these tests can than be compared with the given test vectors to see if tests fail or pass Now "don't care" input and outputs can be masked in the compare process to allow a zero and an one.

Do we have a bug here of are "don't care" characters not intended to be used on gate inputs?