Some business applications are interactive, i.e., they have a graphical user interface or user interface and users can query/modify/input data and view results instantaneously. They can also run reports instantaneously. Some business applications run in batch mode: they are set up to run based on a predetermined event/time and a business user does not need to initiate them or monitor them.
While automation saves you a lot of time, it still takes time. You can't run all your tests all the time. It takes too long and would generate an unmanageable analysis and maintenance effort. In my group, we've taken both manual and automation testing to three levels: sanity, end-to-end, and full. In addition to our feature tests, on every code commit, we run a set of high level, cross-feature tests to make sure that a code change in one feature hasn't broken another one. Only then do we run a set of more extended tests specific to the feature for which the code was committed. Then, we run our suite of feature-level sanity tests on our continuous delivery environment every three hours to make sure all features are in good shape. We only do this on one browser though, because we've found that if a test fails, it doesn't usually depend on the browser. Finally, we run feature end-to-end testing on our nightly environment.
Paying bills isn't as much fun as sending out invoices, but it has to be done. You may already be managing this task through your bank's website, which may or may not excel at this service. There are few other options online for standalone bill-pay, and the ones that exist have restrictions. Bill.com rules when it comes to supporting both invoices and bills; you'll be charged $29 per user per month for payables automation only. If that's more than you want to pay, you could subscribe to Wave, which is free, and just use its bill-paying tools.
Selenium is possibly the most popular open-source test automation framework for Web applications. Being originated in the 2000s and evolved over a decade, Selenium has been an automation framework of choice for Web automation testers, especially for those who possess advanced programming and scripting skills. Selenium has become a core framework for other open-source test automation tools such as Katalon Studio, Watir, Protractor, and Robot Framework.