test: verify tracing channel doesn't swallow unhandledRejection

Add a test to verify that TracingChannel.tracePromise doesn't swallow
unhandledRejection events in case no then/catch handler is set by user.
PR-URL: #59974
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>

Author: Flarna

test/parallel/test-diagnostics-channel-tracing-channel-promise-unhandled.js

@@ -0,0 +1,38 @@
+'use strict';
+
+constcommon=require('../common');
+constdc=require('diagnostics_channel');
+constassert=require('assert');
+
+constchannel=dc.tracingChannel('test');
+
+constexpectedError=newError('test');
+constinput={foo: 'bar'};
+constthisArg={baz: 'buz'};
+
+process.on('unhandledRejection',common.mustCall((reason)=>{
+assert.deepStrictEqual(reason,expectedError);
+}));
+
+functioncheck(found){
+assert.deepStrictEqual(found,input);
+}
+
+consthandlers={
+start: common.mustCall(check),
+end: common.mustCall(check),
+asyncStart: common.mustCall(check),
+asyncEnd: common.mustCall(check),
+error: common.mustCall((found)=>{
+check(found);
+assert.deepStrictEqual(found.error,expectedError);
+})
+};
+
+channel.subscribe(handlers);
+
+// Set no then/catch handler to verify unhandledRejection happens
+channel.tracePromise(function(value){
+assert.deepStrictEqual(this,thisArg);
+returnPromise.reject(value);
+},input,thisArg,expectedError);