Encapsulate ExpectationResult

src/core/ExpectationResult.js

@@ -1,20 +1,20 @@
 //TODO: expectation result may make more sense as a presentation of an expectation.
 jasmine.ExpectationResult = function(params) {
-  this.type = 'expect';
-  this.matcherName = params.matcherName;
-  this.passed_ = params.passed;
-  this.expected = params.expected;
-  this.actual = params.actual;
-  this.message = this.passed_ ? 'Passed.' : params.message;
-
+  var self = this;
   var trace = (params.trace || new Error(this.message));
-  this.trace = this.passed_ ? '' : trace;
-};
-
-jasmine.ExpectationResult.prototype.toString = function () {
-  return this.message;
-};
-
-jasmine.ExpectationResult.prototype.passed = function () {
-  return this.passed_;
+  var message = params.passed ? 'Passed.' : params.message;
+  return jasmine.util.extend(self, {
+    type: 'expect',
+    matcherName: params.matcherName,
+    expected: params.expected,
+    actual:  params.actual,
+    message: message,
+    trace: params.passed ? '' : trace,
+    toString: function() {
+      return message;
+    },
+    passed: function() {
+      return params.passed;
+    }
+  });
 };