cpython/Lib/test/json_tests/test_dump.py

from io import StringIO
from test.json_tests import PyTest, CTest

from test.support import bigmemtest, _1G

class TestDump:
    def test_dump(self):
        sio = StringIO()
        self.json.dump({}, sio)
        self.assertEqual(sio.getvalue(), '{}')

    def test_dumps(self):
        self.assertEqual(self.dumps({}), '{}')

    def test_encode_truefalse(self):
        self.assertEqual(self.dumps(
                 {True: False, False: True}, sort_keys=True),
                 '{"false": true, "true": false}')
        self.assertEqual(self.dumps(
                {2: 3.0, 4.0: 5, False: 1, 6: True}, sort_keys=True),
                '{"false": 1, "2": 3.0, "4.0": 5, "6": true}')

    # Issue 16228: Crash on encoding resized list
    def test_encode_mutated(self):
        a = [object()] * 10
        def crasher(obj):
            del a[-1]
        self.assertEqual(self.dumps(a, default=crasher),
                 '[null, null, null, null, null]')


class TestPyDump(TestDump, PyTest): pass

class TestCDump(TestDump, CTest):

    # The size requirement here is hopefully over-estimated (actual
    # memory consumption depending on implementation details, and also
    # system memory management, since this may allocate a lot of
    # small objects).

    @bigmemtest(size=_1G, memuse=1)
    def test_large_list(self, size):
        N = int(30 * 1024 * 1024 * (size / _1G))
        l = [1] * N
        encoded = self.dumps(l)
        self.assertEqual(len(encoded), N * 3)
        self.assertEqual(encoded[:1], "[")
        self.assertEqual(encoded[-2:], "1]")
        self.assertEqual(encoded[1:-2], "1, " * (N - 1))