cmHSSITestmode is a read-only enumeration reporting whether the DCE side of a HSSI port is currently in a test/loopback mode (on) or in normal operation (off). An administrator checks this alongside cmHSSILoopback when a HSSI circuit isn't passing traffic, to rule out that the far-end DCE equipment has been left in a test state. For example, if a HSSI port won't pass data and cmHSSITestmode reads on(2), the operator would ask the carrier or CSU/DSU operator to take that device out of test mode.