How to safely assert that no shared preferences are present

I tried to find out how to safely assert that preferences aren't stored anywhere. It seems that haven't understood the caching mechanism yet and the docs don开发者_高级运维't clarify it. This is what I did:

File prefsFile = new File("/data/data/"+context.getPackageName() + "/shared_prefs/"
    + context.getPackageName() + "_preferences.xml");
prefsFile.delete();
assertFalse(prefsFile.exists()); // success

// This assertion could fail - why?
assertEquals(0, context.getSharedPreferences(context.getPackageName()+"_preferences",
    MODE_PRIVATE).getAll().size());

Although I deleted the prefs file, it is still possible that getAll().size() returns a non-zero value.

Could someone explain why?

I tried to find out how to safely assert that preferences aren't stored anywhere.

Why?

Could someone explain why?

Off the top of my head:

• You are not actually testing to see if the file exists before deleting it, or if the directory exists
• You are hard-coding a path that may not be correct on all devices
• You are assuming that deleting a file deletes the in-process copy of the SharedPreferences
• You are not bothering to look at the HashMap returned by getAll() to see if your data is there, or if it is some system-supplied initial values

If you want to clear out SharedPreferences, do not try deleting the file. Either call edit().clear().commit() or edit().clear().apply() on your SharedPreferences object.