Extracting an integer value from a JSON string

It is necessary to implement the get_value function, which takes a JSON-formatted string and returns the integer parameter contained within.

def get_value(json_string):
    pass

# Tests
import unittest

class GetValueTests(unittest.TestCase):
    def test_basic(self):
        self.assertEqual(get_value('{"value":42}'), 42)

if __name__ == '__main__':
    unittest.main()