Python unittest, running only the tests that failed

I have a large python test file using unittest that I run from the command line. Some tests take a while to run. This is a mild pain point because I'm often only concerned with the last test I added. What I want is this:

1. add test.
2. run tests (one fails because I haven't written the code to make it pass)
3. implement the behaviour
4. run only the test that failed last time
5. fix the silly error I made when implementing the code
6. run only the failing test, which passes this time
7. run all the tests to find out what I broke.

Is it possible to do this from the command line?