Added docblock to _configCache()
Made assertions in testNonFatalErrorsWithCacheDisable.
To avoid "R" (Risky)  in phpunit.
Merge pull request #4374 from kimegede/cache-test-update

Cache test update
Added assertion for PluginTest::testIgnoreMissingFiles()
Renamed testProvider() to ExceptionProvider().
And updated docblock @return
False tests

* False risky fix - testAuthNoAuth() is never calling write.
* ControllerTestCaseTest::testTestActionWithMultipleRedirect() not asserting anything...
* SessionHelperTest::testFlashIncomplete() not asserting anything...
* ResultSetTest::testRewind() not asserting anything...