Devs must be able to change a test after it has been created and put into the central repository of tests (possibly by someone else).
For example, it could be that the steps of the test now need to be carried out in a slightly different way, by pushing different buttons at different times, or invoking different scripts with different arguments.
Or, it could be that there is a new behaviour that was introduced which should be tested by that test.
Or, it could be that a script now generates a slightly different output that still fulfills the same intent as before, and that therefore, the assertion checks on the output have to be changed.
All of the above need to be supported.