tests: use more complex file storage test
The previous test was attempting to to test delta storage behavior.
It didn't do a very good job at it because there was a good chance
a delta wasn't being used in storage.
Let's switch the test to yield a delta in storage so an upcoming
change to delegate delta logic to storage has the desired effect.
Differential Revision: https://phab.mercurial-scm.org/D4723
{
// Enforcing
"eqeqeq" : true, // true: Require triple equals (===) for comparison
"forin" : true, // true: Require filtering for..in loops with obj.hasOwnProperty()
"freeze" : true, // true: prohibits overwriting prototypes of native objects such as Array, Date etc.
"nonbsp" : true, // true: Prohibit "non-breaking whitespace" characters.
"undef" : true, // true: Require all non-global variables to be declared (prevents global leaks)
// Environments
"browser" : true // Web Browser (window, document, etc)
}