Do you run tests before checking in?

If not, why not?

That the CI will (should) run them is not an excuse for you not to.

I think it's right - but haven't checked, is not professional or good enough.

Even worse than simply relying on the CI to run all the tests of the work you've done is asking for someone else to review the changes before the CI has even run the automated checks against it. 

How would you feel if I asked you to review some of the work I've done but haven't verified it's correct and doesn't break some other part of the system?

The same applies to linting or ensuring that code meets the defined standards and formats. You shouldn't be relying on something checking this after you've said you have finished.
You really should be using tooling that does this as you go.

Some test suites do take a very long time to run. Have you tried running only the tests related to the area you're working on?

If your test suite takes too long to run:

- Have you run the bits relevant to your changes?

- What work is being done (or planned) by you and your team to make the test suite run faster?