CLI: Ensure an unhandled rejection results in a failed test.

bin/run.js

@@ -33,6 +33,11 @@ function run( args, options ) {
 		}
 	} );
 
+	// Listen for unhandled rejections, and call QUnit.onError.
+	process.on( "unhandledRejection", function( reason ) {
+		QUnit.onError( reason );
+	} );
+
 	const files = utils.getFilesFromArgs( args );
 
 	QUnit = requireQUnit();

reporter/html.js

@@ -979,5 +979,4 @@ export function escapeText( s ) {
 
 		return ret;
 	};
-
 }() );

test/cli/fixtures/expected/tap-outputs.js

@@ -89,6 +89,22 @@ Available custom reporters from dependencies are: npm-reporter
 	/* eslint-disable max-len */
 	"qunit hanging-test": `Error: Process exited before tests finished running
 Last test to run (hanging) has an async hold. Ensure all assert.async() callbacks are invoked and Promises resolve. You should also set a standard timeout via QUnit.config.testTimeout.
-`
+`,
 	/* eslint-enable max-len */
+	"qunit unhandled-rejection.js":
+`TAP version 13
+not ok 1 Unhandled Rejections > test passes just fine, but has a rejected promise
+  ---
+  message: "Error thrown in non-returned promise!"
+  severity: failed
+  actual: null
+  expected: undefined
+  stack: undefined:undefined
+  ...
+1..1
+# pass 0
+# skip 0
+# todo 0
+# fail 1
+`
 };

test/cli/fixtures/unhandled-rejection.js

@@ -0,0 +1,19 @@
+"use strict";
+
+QUnit.module( "Unhandled Rejections", function() {
+	QUnit.test( "test passes just fine, but has a rejected promise", function( assert ) {
+		assert.ok( true );
+
+		const done = assert.async();
+
+		new Promise( function( resolve ) {
+			setTimeout( resolve );
+		} )
+			.then( function() {
+				throw new Error( "Error thrown in non-returned promise!" );
+			} );
+
+		// prevent test from exiting before unhandled rejection fires
+		setTimeout( done, 10 );
+	} );
+} );

test/cli/main.js

@@ -105,6 +105,22 @@ QUnit.module( "CLI Main", function() {
 		}
 	} ) );
 
+	QUnit.test( "unhandled rejections fail tests", co.wrap( function* ( assert ) {
+		const command = "qunit unhandled-rejection.js";
+
+		try {
+			const result = yield execute( command );
+			assert.pushResult( {
+				result: false,
+				actual: result.stdout
+			} );
+		} catch ( e ) {
+			assert.equal( e.code, 1 );
+			assert.equal( e.stderr, "" );
+			assert.equal( e.stdout, expectedOutput[ command ] );
+		}
+	} ) );
+
 	QUnit.module( "filter", function() {
 		QUnit.test( "can properly filter tests", co.wrap( function* ( assert ) {
 			const command = "qunit --filter 'single' test single.js 'glob/**/*-test.js'";