fix test

Author: tinayuangao

src/lib/radio/radio.ts

@@ -185,6 +185,7 @@ export class MdRadioGroup extends _MdRadioGroupMixinBase
   set disabled(value) {
     this._disabled = value;
     if (this._radios) {
+      // Update radios disabled state
       this._radios.forEach((r) => r._groupValueChanged());
     }
   }
@@ -400,9 +401,10 @@ export class MdRadioButton implements OnInit, AfterViewInit, OnDestroy {
   get disabled(): boolean {
     return this._disabled || (this.radioGroup != null && this.radioGroup.disabled);
   }
-
   set disabled(value: boolean) {
     this._disabled = coerceBooleanProperty(value);
+    // Update rippleDisabled
+    this._changeDetector.markForCheck();
   }
 
   /**