Add tests for formatting empty content errors.

spec/core/ExceptionFormatterSpec.js

@@ -37,7 +37,7 @@ describe("ExceptionFormatter", function() {
       expect(message).toEqual('A Classic Mistake: you got your foo in my bar');
     });
 
-    it('formats thrown exceptions with message but no name', function() {
+    it('formats unnamed exceptions with message', function() {
       var unnamedError = {message: 'This is an unnamed error message.'};
 
       var exceptionFormatter = new jasmineUnderTest.ExceptionFormatter(),
@@ -46,6 +46,19 @@ describe("ExceptionFormatter", function() {
       expect(message).toEqual('This is an unnamed error message.');
     });
 
+    it('formats empty exceptions with toString format', function() {
+      var EmptyError = function() {};
+      EmptyError.prototype.toString = function() {
+        return '[EmptyError]';
+      };
+      var emptyError = new EmptyError();
+
+      var exceptionFormatter = new jasmineUnderTest.ExceptionFormatter(),
+          message = exceptionFormatter.message(emptyError);
+
+      expect(message).toEqual('[EmptyError] thrown');
+    });
+
     it("formats thrown exceptions that aren't errors", function() {
       var thrown = "crazy error",
           exceptionFormatter = new jasmineUnderTest.ExceptionFormatter(),