Using Coverage in Flask framework, to be run along with the tests

manage.py

# Created with a NoneType
cov = None

if os.environ.get('COVERAGE'):
    import coverage
    # an instance of the coverage.coverage() class is created, using a probable "from_" function of the Coverage class
    cov = coverage.coverage(branch=True, include='gasify/*')
    cov.start()

app = create_app('default')

manager = Manager(app)
migrate = Migrate(app, db)


@manager.command
# using flask scripts, we can add a Boolean argument to the custom commands created, in this case coverage=False
def test(coverage=False):
    """Run the unittest"""

    # when the "COVERAGE" env variable is set, the scripts is restarted
    # and the cov.start() method is called again
    if coverage and not os.environ.get('COVERAGE'):
        import sys
        os.environ['COVERAGE'] = '1'
        os.execvp(sys.executable, [sys.executable] + sys.argv)

    import unittest
    tests = unittest.TestLoader().discover('tests')
    unittest.TextTestRunner(verbosity=2).run(tests)

    if cov:
        # after the "cov" variable is no longer None, and the Coverage instance has been created, the cov.stop() is called
        cov.stop()
        # then the coverage results is saved
        cov.save()
        print('Coverage summary: ')
        # Generate the results, on the CLI
        cov.report()
        # the basedir is created to point to the location of this file
        basedir = os.path.abspath(os.path.dirname(__file__))
        # covdir is the location of the coverage directory within the basedir
        covdir = os.path.join(basedir, 'tmp/coverage')
        # html report is generated at the covdir 
        cov.html_report(directory=covdir)
        print('HTML version: file://%s/index.html' % covdir)
        # erase the results
        cov.erase()