Hardware testing of the 1:1 connection for opens and shorts

Question

I have a board (DUT = device under test), featuring (in addition to other things, which are not important for this question) 2 connectors - A and B. The connectors are connected 1:1 at the DUT.

 +--------------+  
 |      DUT     |
-|A1----------B1|-
-|A2----------B2|-
-|A3----------B3|-
-|A4----------B4|-
-|A5----------B5|-
 |              |
 +--------------+  

I need to test, that the signal path of these two connectors are not open and ideally as a bonus, also they are not shorted. My intention is to use a GPIO board, which I have an experience with.

Test approach for first 2 pins of each connector:

loopback    +-----------+     GPIO board          
       |----|A1| DUT |B1|---- O                   
       |----|A2|     |B2|---- I                  
            +-----------+                        

1. A1 and A2 pins are shortened using a hardware loopback
2. B1 pin is set to output at the GPIO board, pin B2 to input
3. The output pin is set to H and then to L accordingly. The same states are expected to be read at the input pin.

Test approach for the latter 3 pins of each connector:

As the total number of the pins is not even, the remaining odd number of pins would be shortened and tested together:

loopback    +-----------+     GPIO board          
       |----|A3| DUT |B3|---- O                   
       |----|A4|     |B4|---- I                  
       |----|A5|     |B5|---- I                  
            +-----------+                        

1. A3, A4 and A5 pins are shorted together with a hardware loopback
2. B3 pin is set to output at the GPIO board, pins B4 and B5 to input
3. The test step would be similar to the previous state with 2 pins, just two outputs will be read at once.

My questions are:

1. This approach will test, if there are any opens in the DUT signal paths. Is this approach robust enough to test any potential opens?
2. This approach will not test any potential shorts. Is there any additional easy approach to test for the shorts also?

Answer 1

If you want to verify no wires are open and no wires are shorted but not verify that the end-to-end wiring is correct (for example, pin 1 on one end is not connected to pin 2 on the other end instead), you could do a two-step approach.

Test 1 is done with the far end disconnected. Run through each line, setting that line high and verifying that all other lines input low. This tests for shorts.

Test 2 is done by shorting together the far end pins, as you specified. Here, it is sufficient to set one line high and verify that all other lines read high.

To avoid noise, all inputs must have pull-down resistors, but not so large small a value that all put in parallel won't overload the output.