Cleanup of mjsunit.js code and make assertEquals more strict.

test/mjsunit/mirror-number.js

 // Copyright 2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 32 matching lines @@
   assertTrue(mirror.isNumber());
   assertEquals('number', mirror.type());
   assertTrue(mirror.isPrimitive());
 
   // Test text representation
   assertEquals(String(n), mirror.toText());
 
   // Parse JSON representation and check.
   var fromJSON = eval('(' + json + ')');
   assertEquals('number', fromJSON.type);
-  if (!isNaN(n)) {
+  if (isFinite(n)) {
     assertEquals(n, fromJSON.value);
   } else {
-    // NaN values are encoded as strings.
+    // NaN and Infinity values are encoded as strings.
     assertTrue(typeof fromJSON.value == 'string');
     if (n === Infinity) {
       assertEquals('Infinity', fromJSON.value);
     } else if (n === -Infinity) {
       assertEquals('-Infinity', fromJSON.value);
     } else {
       assertEquals('NaN', fromJSON.value);
     }
   }
 }
 
 
 // Test a number of different numbers.
 testNumberMirror(-7);
 testNumberMirror(-6.5);
 testNumberMirror(0);
 testNumberMirror(42);
 testNumberMirror(100.0002);
 testNumberMirror(Infinity);
 testNumberMirror(-Infinity);
 testNumberMirror(NaN);