This CoriantTypesTestSignalType value (default NONE) selects which standard test pattern a 10G WAN PHY client port framed as SONET generates when test-signal mode is active, used to verify the facility independent of live customer traffic. An administrator selects a specific test pattern to match what the test equipment or far-end node expects to receive during commissioning or fault isolation. For example, a technician bringing up 10G WAN SONET for the first time might select a defined test pattern here so a test set on the far end can verify bit-error performance before real traffic is switched on.