test($compile): extend $onChanges() test to account for one more case

Discussed in https://github.com/angular/angular.js/pull/15098/files#r77770755.

Author: gkalpak

test/ng/compileSpec.js

@@ -4357,7 +4357,7 @@ describe('$compile', function() {
                   this.$onChanges = onChangesSpy;
                 }
               });
-          });
+            });
 
             inject(function($compile, $rootScope) {
               var template = '<test prop="a" attr="{{a}}"></test>' +
@@ -4377,6 +4377,19 @@ describe('$compile', function() {
                 prop: jasmine.objectContaining({currentValue: NaN}),
                 attr: jasmine.objectContaining({currentValue: 'NaN'})
               });
+
+              onChangesSpy.calls.reset();
+              $rootScope.$apply('a = "bar"; b = 42');
+
+              expect(onChangesSpy).toHaveBeenCalledTimes(2);
+              expect(onChangesSpy.calls.argsFor(0)[0]).toEqual({
+                prop: jasmine.objectContaining({previousValue: 'foo', currentValue: 'bar'}),
+                attr: jasmine.objectContaining({previousValue: 'foo', currentValue: 'bar'})
+              });
+              expect(onChangesSpy.calls.argsFor(1)[0]).toEqual({
+                prop: jasmine.objectContaining({previousValue: NaN, currentValue: 42}),
+                attr: jasmine.objectContaining({previousValue: 'NaN', currentValue: '42'})
+              });
             });
           });