mbed-os/tools/test_configs/no_network.json

{
    "config": {
        "echo-server-addr" : {
            "help" : "IP address of echo server",
            "value" : null
        },
        "echo-server-port" : {
            "help" : "Port of echo server",
            "value" : null
        }
    },
    "target_overrides": {
        "*": {
            "target.network-default-interface-type": null
        }
    }
}