import random
import unittest

def get_random_line(filename):
    lines = []

    with open(filename) as f:
        for line in f:
            lines.append(line)

    return random.choice(lines)


class TestRandomLine(unittest.TestCase):
    def test_random_line(self):
        filename = 'test.txt'
        lines = 10

        with open(filename, 'w') as f:
            for i in range(lines):
                f.write('line number {0}\n'.format(i))

        seed = 1
        random.seed(seed)
        rand_num = random.randrange(lines)
        with open(filename) as f:
            line1 = ''
            for i in range(rand_num + 1):
                line1 = f.readline()

        random.seed(seed)
        line2 = get_random_line(filename)
        self.assertEqual(line1, line2)

        random.seed(seed + 1)
        line3 = get_random_line(filename)
        self.assertNotEqual(line1, line3)

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