what happens with Schedule job and other processes during salesforce maintenance

There is no impact on the scheduled jobs, batch, scheduled, long-running transactions, or bulk API jobs prior to the maintenance. Salesforce will queue all jobs and process them once the maintenance is complete.

You can find more detailed explanation in this link: https://help.salesforce.com/apex/HTViewSolution?urlname=How-is-my-org-impacted-during-Salesforce-maintenance&language=en_US

In context of Test cases and deployment

• Salesforce saves the results of executed tests in chunks. Therefore, a small portion of tests might not have their results saved because they weren’t part of the last saved chunk. These tests are rerun when the deployment is restarted.

• If the deployment interruption happens before tests have started, the entire deployment restarts from the beginning.