title: Unit test coverage report for tests written using unittest and pytest package
body: <p>In the project that I am currently working on, I have few of my colleagues who have written unit tests using unittest package and some using pytest package. When I run unit tests in CI pipeline, I invoke all of the unit tests. But, we now also need to get overall code coverage package. So, I have updated unit test invocation script by adding coverage (Please see script snippet below). But, I see that when I run below script I get coverage output of <code>coverage run -a -m pytest -v -m unittests</code> (line 7 below) only not the tests run before. But, if I remove the line <code>coverage run -a -m pytest -v -m unittests</code> (line 7 below), I get output of previous unit tests.</p>
  <pre><code>#!/bin/bash
  set -xe
  coverage run -m unittest test_a.py
  coverage run -a -m unittest test_b.py
  coverage run -a -m unittest test_c.py
  ...
  cd process/tests/
  coverage run -a -m pytest -v -m unittests
  coverage report -m --omit=*/venv/*
  </code></pre>
  <p>coverage only reports the output of <code>coverage run -a -m pytest -v -m unittests</code> ignoring the previously run unit tests.</p>
  <p>Can I please know how can I get a single report for all unit tests in above scenario?</p>