Tests: Update CLI test and test fixture to remove stacktrace ambiguity.

Unfortunately, we cannot use real errors here because the stack trace
representation changes across Node versions (and therefore the
expectations fail).

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

@@ -1,3 +1,7 @@
+"use strict";
+
+const path = require( "path" );
+
 // Expected outputs from the TapReporter for the commands run in CLI tests
 module.exports = {
 	"qunit":
@@ -97,21 +101,25 @@ not ok 1 Unhandled Rejections > test passes just fine, but has a rejected promis
   ---
   message: "Error thrown in non-returned promise!"
   severity: failed
-  actual: {}
+  actual: {
+  "message": "Error thrown in non-returned promise!",
+  "stack": "Error: Error thrown in non-returned promise!\\n    at /some/path/wherever/unhandled-rejection.js:13:11"
+}
   expected: undefined
   stack: Error: Error thrown in non-returned promise!
-    at /Users/rjackson/src/open-source/qunit/test/cli/fixtures/unhandled-rejection.js:13:11
-    at <anonymous>
+    at /some/path/wherever/unhandled-rejection.js:13:11
   ...
 not ok 2 global failure
   ---
   message: "outside of a test context"
   severity: failed
   actual: {
-  "message": "outside of a test context"
+  "message": "outside of a test context",
+  "stack": "Error: outside of a test context\\n    at Object.<anonymous> (/some/path/wherever/unhandled-rejection.js:20:18)"
 }
   expected: undefined
-  stack:     at runTest (/Users/rjackson/src/open-source/qunit/dist/qunit.js:1478:30)
+  stack: Error: outside of a test context
+    at Object.<anonymous> (/some/path/wherever/unhandled-rejection.js:20:18)
   ...
 1..2
 # pass 0

test/cli/fixtures/unhandled-rejection.js

@@ -10,12 +10,25 @@ QUnit.module( "Unhandled Rejections", function() {
 			setTimeout( resolve );
 		} )
 			.then( function() {
-				throw new Error( "Error thrown in non-returned promise!" );
+
+				// throwing a non-Error here because stack trace representation
+				// across Node versions is not stable (they continue to get better)
+				throw {
+					message: "Error thrown in non-returned promise!",
+					stack: `Error: Error thrown in non-returned promise!
+    at /some/path/wherever/unhandled-rejection.js:13:11`
+				};
 			} );
 
 		// prevent test from exiting before unhandled rejection fires
 		setTimeout( done, 10 );
 	} );
 
-	Promise.reject( { message: "outside of a test context" } );
+	// rejecting with a non-Error here because stack trace representation
+	// across Node versions is not stable (they continue to get better)
+	Promise.reject( {
+		message: "outside of a test context",
+		stack: `Error: outside of a test context
+    at Object.<anonymous> (/some/path/wherever/unhandled-rejection.js:20:18)`
+	} );
 } );