Constant SYSTEM_HELLO_REQUEST_JSON 

pub const SYSTEM_HELLO_REQUEST_JSON: &str = "{\n  \"jsonrpc\": \"2.0\",\n  \"id\": \"hello-1\",\n  \"method\": \"system.hello\",\n  \"params\": {\n    \"client\": {\n      \"name\": \"fixture-client\",\n      \"version\": \"0.1.0\"\n    },\n    \"protocol\": {\n      \"ranges\": [\n        {\n          \"major\": 1,\n          \"minMinor\": 0,\n          \"maxMinor\": 5\n        },\n        {\n          \"major\": 3,\n          \"minMinor\": 0,\n          \"maxMinor\": 0\n        }\n      ]\n    },\n    \"features\": {\n      \"required\": [],\n      \"optional\": [\n        \"action.protected.v1\",\n        \"device.routing.v1\",\n        \"device.semanticActions.v1\",\n        \"events.snapshot.v1\",\n        \"events.stream.v1\",\n        \"media.stream.v1\",\n        \"observation.uiSnapshot.v1\",\n        \"request.control.v1\",\n        \"session.export.page.v1\",\n        \"verdict.record.v1\"\n      ]\n    }\n  }\n}\n";

Canonical system.hello request fixture.