Having a passing test suite or CI pipeline doesn't tell you if your appliction works.
There could be scenarios or edge-cases that aren't covered within the test suite and contain bugs, but aren't covered by the test suite.
There could be untested code that isn't covered at all.
A passing test suite proves that the tests that have been written so far pass and that there are no regressions introduced by the latest change.
## Here's the thing
Instead of telling you that your application works by passing, the test suite tells you something is broken when it fails.
If a previously-passing test is failing, the application is broken and should not be deployed - not that the application is working if the tests don't fail.
