fix: firefox ut failures in worker comm

Author: abose

src/worker/WorkerComm.js

@@ -293,7 +293,9 @@
                     }
                 }
             } catch (err) {
-                response.err = err.stack || err.toString();
+                response.err = err.message || err.stack ?
+                    {message: err.message, stack: err.stack}
+                    : err.toString();
             }
             postTarget.postMessage(JSON.stringify(response));
         }

test/spec/WorkerComm-test.js

@@ -48,7 +48,7 @@ define(function (require, exports, module) {
         });
 
         afterAll(function () {
-            //_myWorker.terminate();
+            _myWorker.terminate();
         });
 
         describe("execPeer API tests", function () {
@@ -69,7 +69,7 @@ define(function (require, exports, module) {
                 } catch (e) {
                     thrown = e;
                 }
-                expect(thrown.startsWith("Error: oops")).toBeTrue();
+                expect(thrown.message).toBe("oops");
             });
 
             it("Should throw if promise rejected in worker", async function () {
@@ -95,7 +95,7 @@ define(function (require, exports, module) {
                     throw new Error("throw_me");
                 });
                 let result = await exports.execPeer("execAndRejectInMainThread");
-                expect(result.startsWith("Error: throw_me")).toBeTrue();
+                expect(result.message).toBe("throw_me");
             });
         });