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Vincent Palatin and I have some fairly simple instructions on how to test to see if a USB Type-A to Type-C cable, or a USB Type-B receptacle to Type-C adapter is spec compliant.
The both of us are on the Pixel team, so these instructions are only for people who have Chromebook Pixel 2015 laptops.
Put it into dev mode. Plug in the suspect USB cable and plug the other end into a DCP charging wall wart (preferably one you don't have any sort of sentimental attachment to)
From a root shell run this :
ectool --name=cros_pd usbpdpower 0
Here's a good cable :
localhost ~ # ectool --name=cros_pd usbpdpower
Port 0: SNK Charger DCP 4920mV / 2000mA, max 5000mV / 2000mA / 10000mW
Port 1: Disconnected
Here's a bad cable :
localhost ~ # ectool --name=cros_pd usbpdpower
Port 0: SNK Charger Type-C 5147mV / 3000mA, max 5000mV / 3000mA / 15000mW
Port 1: Disconnected
In the bad case, it shows up as Type-C with a 3000mA max, which means the resistor setting is wrong. You'll know when it's using a "Default USB Power" setting because after SNK Charger, you'll see something in this set of possibilities :
