It DOES work…

For those who complain about the read-only issue: right click on the drive or device in question, select “get info” and go down to the very bottom and grant read-write access to “everyone” and the test will run just fine. Make sure you reset your “everyone” back to read-only when finished.

Standard results that I’ve tested are:
USB 2.0 = ~33 Mbps
SATA II = ~33 Mbps
WD MyCloud (1 Gbps connection) = ~40 Mbps
USB 3.0 = 100 or greater Mbps depending on device quality
Internal SATA III HD = ~100 Mbps
Internal SATA III SSD = ~500 Mbps

These are all in-line with industry expected results.

Sabino2son about Blackmagic Disk Speed Test, v2.2.2