How to test a site (server) for fault tolerance?

Question

stress testing

Installed Debian+Wordpress+Woocommerce server on VPS. Set up.
Didn't do anything exotic - everything is more than standard. Everything worked fine, but after 3 days, for unknown reasons, the server "fell". What is there to fall when almost nothing is installed there is not clear.
Wordpress writes - I can't connect to the database, I can't access it via ftp - it's not clear what happened.
Rebooted the server. Does not work. Rebooted the second time - everything worked.
I don't like this situation.
How to test a site (server) for fault tolerance?
But preferably over a relatively long period of time. Not an hour or two like loadimpact and analogues.
PS
Hoster replied.
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All maintenances from node side you can always check on this page: https://billing.time4vps.eu/status/ It seems that was an issue not from node side. Could you check your server logs files? You should see more information about the cause of this issue. I would recommend using our prepared instruction: https://community.time4vps.eu/discussion/339/how-t...
If you have any further question, do not hesitate to contact us again. Have a nice day!
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From the links you can see that on April 6 something fell on them. But like, they write that it's not mine.
I fell from 6 to 8 April. It is not known exactly when.
Logs if you're interested.
https://cloud.mail.ru/public/Mqig/6JyugTAYU/LOGS/

Answer 1

Maybe the hoster did something with physical. server...
Monitor and/or ask the hoster: if this happens periodically, change the VPS hoster.

Answer 2

you have already tested.
the result is negative.
what else do you need?

Answer 3

Yandex.Tank as an option