I have been thinking about the core of a sure testimony of the restored gospel. It seems to me that a truly solid testimony of Mormonism must be based on personal revelation from God confirming a couple of things:
1. That God exists and is worthy of worship and emulation, and
2. That God inspired the founding of Mormonism and is currently guiding the church
That’s it. I submit that all the other stuff people focus on in publicly expressed testimonies is less core than these two.
I reckon that if one can personally communicate with God and have God convince them of those two things, one should be sufficiently anchored to handle anything that might otherwise shake their faith in the gospel. Further I think that if one can at any time turn to God and confirm 1 and 2 above one should be permanently inoculated against any surprises one comes across.
Of course if one cannot break through and receive any revelation from God at all then there are bigger problems to deal with than any other issues one has with Mormon culture/history/practices.