diff --git a/Lib/test/test_int.py b/Lib/test/test_int.py
new file mode 100644
index 0000000000..307ca36bb4
--- /dev/null
+++ b/Lib/test/test_int.py
@@ -0,0 +1,521 @@
+import sys
+
+import unittest
+from test import support
+from test.test_grammar import (VALID_UNDERSCORE_LITERALS,
+                               INVALID_UNDERSCORE_LITERALS)
+
+L = [
+        ('0', 0),
+        ('1', 1),
+        ('9', 9),
+        ('10', 10),
+        ('99', 99),
+        ('100', 100),
+        ('314', 314),
+        (' 314', 314),
+        ('314 ', 314),
+        ('  \t\t  314  \t\t  ', 314),
+        (repr(sys.maxsize), sys.maxsize),
+        ('  1x', ValueError),
+        ('  1  ', 1),
+        ('  1\02  ', ValueError),
+        ('', ValueError),
+        (' ', ValueError),
+        ('  \t\t  ', ValueError),
+        ("\u0200", ValueError)
+]
+
+class IntSubclass(int):
+    pass
+
+class IntTestCases(unittest.TestCase):
+
+    def test_basic(self):
+        self.assertEqual(int(314), 314)
+        self.assertEqual(int(3.14), 3)
+        # Check that conversion from float truncates towards zero
+        self.assertEqual(int(-3.14), -3)
+        self.assertEqual(int(3.9), 3)
+        self.assertEqual(int(-3.9), -3)
+        self.assertEqual(int(3.5), 3)
+        self.assertEqual(int(-3.5), -3)
+        self.assertEqual(int("-3"), -3)
+        self.assertEqual(int(" -3 "), -3)
+        self.assertEqual(int("\N{EM SPACE}-3\N{EN SPACE}"), -3)
+        # Different base:
+        self.assertEqual(int("10",16), 16)
+        # Test conversion from strings and various anomalies
+        for s, v in L:
+            for sign in "", "+", "-":
+                for prefix in "", " ", "\t", "  \t\t  ":
+                    ss = prefix + sign + s
+                    vv = v
+                    if sign == "-" and v is not ValueError:
+                        vv = -v
+                    try:
+                        self.assertEqual(int(ss), vv)
+                    except ValueError:
+                        pass
+
+        s = repr(-1-sys.maxsize)
+        x = int(s)
+        self.assertEqual(x+1, -sys.maxsize)
+        self.assertIsInstance(x, int)
+        # should return int
+        self.assertEqual(int(s[1:]), sys.maxsize+1)
+
+        # should return int
+        x = int(1e100)
+        self.assertIsInstance(x, int)
+        x = int(-1e100)
+        self.assertIsInstance(x, int)
+
+
+        # SF bug 434186:  0x80000000/2 != 0x80000000>>1.
+        # Worked by accident in Windows release build, but failed in debug build.
+        # Failed in all Linux builds.
+        x = -1-sys.maxsize
+        self.assertEqual(x >> 1, x//2)
+
+        x = int('1' * 600)
+        self.assertIsInstance(x, int)
+
+
+        self.assertRaises(TypeError, int, 1, 12)
+
+        self.assertEqual(int('0o123', 0), 83)
+        self.assertEqual(int('0x123', 16), 291)
+
+        # Bug 1679: "0x" is not a valid hex literal
+        self.assertRaises(ValueError, int, "0x", 16)
+        self.assertRaises(ValueError, int, "0x", 0)
+
+        self.assertRaises(ValueError, int, "0o", 8)
+        self.assertRaises(ValueError, int, "0o", 0)
+
+        self.assertRaises(ValueError, int, "0b", 2)
+        self.assertRaises(ValueError, int, "0b", 0)
+
+        # SF bug 1334662: int(string, base) wrong answers
+        # Various representations of 2**32 evaluated to 0
+        # rather than 2**32 in previous versions
+
+        self.assertEqual(int('100000000000000000000000000000000', 2), 4294967296)
+        self.assertEqual(int('102002022201221111211', 3), 4294967296)
+        self.assertEqual(int('10000000000000000', 4), 4294967296)
+        self.assertEqual(int('32244002423141', 5), 4294967296)
+        self.assertEqual(int('1550104015504', 6), 4294967296)
+        self.assertEqual(int('211301422354', 7), 4294967296)
+        self.assertEqual(int('40000000000', 8), 4294967296)
+        self.assertEqual(int('12068657454', 9), 4294967296)
+        self.assertEqual(int('4294967296', 10), 4294967296)
+        self.assertEqual(int('1904440554', 11), 4294967296)
+        self.assertEqual(int('9ba461594', 12), 4294967296)
+        self.assertEqual(int('535a79889', 13), 4294967296)
+        self.assertEqual(int('2ca5b7464', 14), 4294967296)
+        self.assertEqual(int('1a20dcd81', 15), 4294967296)
+        self.assertEqual(int('100000000', 16), 4294967296)
+        self.assertEqual(int('a7ffda91', 17), 4294967296)
+        self.assertEqual(int('704he7g4', 18), 4294967296)
+        self.assertEqual(int('4f5aff66', 19), 4294967296)
+        self.assertEqual(int('3723ai4g', 20), 4294967296)
+        self.assertEqual(int('281d55i4', 21), 4294967296)
+        self.assertEqual(int('1fj8b184', 22), 4294967296)
+        self.assertEqual(int('1606k7ic', 23), 4294967296)
+        self.assertEqual(int('mb994ag', 24), 4294967296)
+        self.assertEqual(int('hek2mgl', 25), 4294967296)
+        self.assertEqual(int('dnchbnm', 26), 4294967296)
+        self.assertEqual(int('b28jpdm', 27), 4294967296)
+        self.assertEqual(int('8pfgih4', 28), 4294967296)
+        self.assertEqual(int('76beigg', 29), 4294967296)
+        self.assertEqual(int('5qmcpqg', 30), 4294967296)
+        self.assertEqual(int('4q0jto4', 31), 4294967296)
+        self.assertEqual(int('4000000', 32), 4294967296)
+        self.assertEqual(int('3aokq94', 33), 4294967296)
+        self.assertEqual(int('2qhxjli', 34), 4294967296)
+        self.assertEqual(int('2br45qb', 35), 4294967296)
+        self.assertEqual(int('1z141z4', 36), 4294967296)
+
+        # tests with base 0
+        # this fails on 3.0, but in 2.x the old octal syntax is allowed
+        self.assertEqual(int(' 0o123  ', 0), 83)
+        self.assertEqual(int(' 0o123  ', 0), 83)
+        self.assertEqual(int('000', 0), 0)
+        self.assertEqual(int('0o123', 0), 83)
+        self.assertEqual(int('0x123', 0), 291)
+        self.assertEqual(int('0b100', 0), 4)
+        self.assertEqual(int(' 0O123   ', 0), 83)
+        self.assertEqual(int(' 0X123  ', 0), 291)
+        self.assertEqual(int(' 0B100 ', 0), 4)
+
+        # without base still base 10
+        self.assertEqual(int('0123'), 123)
+        self.assertEqual(int('0123', 10), 123)
+
+        # tests with prefix and base != 0
+        self.assertEqual(int('0x123', 16), 291)
+        self.assertEqual(int('0o123', 8), 83)
+        self.assertEqual(int('0b100', 2), 4)
+        self.assertEqual(int('0X123', 16), 291)
+        self.assertEqual(int('0O123', 8), 83)
+        self.assertEqual(int('0B100', 2), 4)
+
+        # the code has special checks for the first character after the
+        #  type prefix
+        self.assertRaises(ValueError, int, '0b2', 2)
+        self.assertRaises(ValueError, int, '0b02', 2)
+        self.assertRaises(ValueError, int, '0B2', 2)
+        self.assertRaises(ValueError, int, '0B02', 2)
+        self.assertRaises(ValueError, int, '0o8', 8)
+        self.assertRaises(ValueError, int, '0o08', 8)
+        self.assertRaises(ValueError, int, '0O8', 8)
+        self.assertRaises(ValueError, int, '0O08', 8)
+        self.assertRaises(ValueError, int, '0xg', 16)
+        self.assertRaises(ValueError, int, '0x0g', 16)
+        self.assertRaises(ValueError, int, '0Xg', 16)
+        self.assertRaises(ValueError, int, '0X0g', 16)
+
+        # SF bug 1334662: int(string, base) wrong answers
+        # Checks for proper evaluation of 2**32 + 1
+        self.assertEqual(int('100000000000000000000000000000001', 2), 4294967297)
+        self.assertEqual(int('102002022201221111212', 3), 4294967297)
+        self.assertEqual(int('10000000000000001', 4), 4294967297)
+        self.assertEqual(int('32244002423142', 5), 4294967297)
+        self.assertEqual(int('1550104015505', 6), 4294967297)
+        self.assertEqual(int('211301422355', 7), 4294967297)
+        self.assertEqual(int('40000000001', 8), 4294967297)
+        self.assertEqual(int('12068657455', 9), 4294967297)
+        self.assertEqual(int('4294967297', 10), 4294967297)
+        self.assertEqual(int('1904440555', 11), 4294967297)
+        self.assertEqual(int('9ba461595', 12), 4294967297)
+        self.assertEqual(int('535a7988a', 13), 4294967297)
+        self.assertEqual(int('2ca5b7465', 14), 4294967297)
+        self.assertEqual(int('1a20dcd82', 15), 4294967297)
+        self.assertEqual(int('100000001', 16), 4294967297)
+        self.assertEqual(int('a7ffda92', 17), 4294967297)
+        self.assertEqual(int('704he7g5', 18), 4294967297)
+        self.assertEqual(int('4f5aff67', 19), 4294967297)
+        self.assertEqual(int('3723ai4h', 20), 4294967297)
+        self.assertEqual(int('281d55i5', 21), 4294967297)
+        self.assertEqual(int('1fj8b185', 22), 4294967297)
+        self.assertEqual(int('1606k7id', 23), 4294967297)
+        self.assertEqual(int('mb994ah', 24), 4294967297)
+        self.assertEqual(int('hek2mgm', 25), 4294967297)
+        self.assertEqual(int('dnchbnn', 26), 4294967297)
+        self.assertEqual(int('b28jpdn', 27), 4294967297)
+        self.assertEqual(int('8pfgih5', 28), 4294967297)
+        self.assertEqual(int('76beigh', 29), 4294967297)
+        self.assertEqual(int('5qmcpqh', 30), 4294967297)
+        self.assertEqual(int('4q0jto5', 31), 4294967297)
+        self.assertEqual(int('4000001', 32), 4294967297)
+        self.assertEqual(int('3aokq95', 33), 4294967297)
+        self.assertEqual(int('2qhxjlj', 34), 4294967297)
+        self.assertEqual(int('2br45qc', 35), 4294967297)
+        self.assertEqual(int('1z141z5', 36), 4294967297)
+
+    def test_underscores(self):
+        for lit in VALID_UNDERSCORE_LITERALS:
+            if any(ch in lit for ch in '.eEjJ'):
+                continue
+            self.assertEqual(int(lit, 0), eval(lit))
+            self.assertEqual(int(lit, 0), int(lit.replace('_', ''), 0))
+        for lit in INVALID_UNDERSCORE_LITERALS:
+            if any(ch in lit for ch in '.eEjJ'):
+                continue
+            self.assertRaises(ValueError, int, lit, 0)
+        # Additional test cases with bases != 0, only for the constructor:
+        self.assertEqual(int("1_00", 3), 9)
+        self.assertEqual(int("0_100"), 100)  # not valid as a literal!
+        self.assertEqual(int(b"1_00"), 100)  # byte underscore
+        self.assertRaises(ValueError, int, "_100")
+        self.assertRaises(ValueError, int, "+_100")
+        self.assertRaises(ValueError, int, "1__00")
+        self.assertRaises(ValueError, int, "100_")
+
+    @support.cpython_only
+    def test_small_ints(self):
+        # Bug #3236: Return small longs from PyLong_FromString
+        self.assertIs(int('10'), 10)
+        self.assertIs(int('-1'), -1)
+        self.assertIs(int(b'10'), 10)
+        self.assertIs(int(b'-1'), -1)
+
+    def test_no_args(self):
+        self.assertEqual(int(), 0)
+
+    def test_keyword_args(self):
+        # Test invoking int() using keyword arguments.
+        self.assertEqual(int('100', base=2), 4)
+        with self.assertRaisesRegex(TypeError, 'keyword argument'):
+            int(x=1.2)
+        with self.assertRaisesRegex(TypeError, 'keyword argument'):
+            int(x='100', base=2)
+        self.assertRaises(TypeError, int, base=10)
+        self.assertRaises(TypeError, int, base=0)
+
+    def test_int_base_limits(self):
+        """Testing the supported limits of the int() base parameter."""
+        self.assertEqual(int('0', 5), 0)
+        with self.assertRaises(ValueError):
+            int('0', 1)
+        with self.assertRaises(ValueError):
+            int('0', 37)
+        with self.assertRaises(ValueError):
+            int('0', -909)  # An old magic value base from Python 2.
+        with self.assertRaises(ValueError):
+            int('0', base=0-(2**234))
+        with self.assertRaises(ValueError):
+            int('0', base=2**234)
+        # Bases 2 through 36 are supported.
+        for base in range(2,37):
+            self.assertEqual(int('0', base=base), 0)
+
+    def test_int_base_bad_types(self):
+        """Not integer types are not valid bases; issue16772."""
+        with self.assertRaises(TypeError):
+            int('0', 5.5)
+        with self.assertRaises(TypeError):
+            int('0', 5.0)
+
+    def test_int_base_indexable(self):
+        class MyIndexable(object):
+            def __init__(self, value):
+                self.value = value
+            def __index__(self):
+                return self.value
+
+        # Check out of range bases.
+        for base in 2**100, -2**100, 1, 37:
+            with self.assertRaises(ValueError):
+                int('43', base)
+
+        # Check in-range bases.
+        self.assertEqual(int('101', base=MyIndexable(2)), 5)
+        self.assertEqual(int('101', base=MyIndexable(10)), 101)
+        self.assertEqual(int('101', base=MyIndexable(36)), 1 + 36**2)
+
+    def test_non_numeric_input_types(self):
+        # Test possible non-numeric types for the argument x, including
+        # subclasses of the explicitly documented accepted types.
+        class CustomStr(str): pass
+        class CustomBytes(bytes): pass
+        class CustomByteArray(bytearray): pass
+
+        factories = [
+            bytes,
+            bytearray,
+            lambda b: CustomStr(b.decode()),
+            CustomBytes,
+            CustomByteArray,
+            memoryview,
+        ]
+        try:
+            from array import array
+        except ImportError:
+            pass
+        else:
+            factories.append(lambda b: array('B', b))
+
+        for f in factories:
+            x = f(b'100')
+            with self.subTest(type(x)):
+                self.assertEqual(int(x), 100)
+                if isinstance(x, (str, bytes, bytearray)):
+                    self.assertEqual(int(x, 2), 4)
+                else:
+                    msg = "can't convert non-string"
+                    with self.assertRaisesRegex(TypeError, msg):
+                        int(x, 2)
+                with self.assertRaisesRegex(ValueError, 'invalid literal'):
+                    int(f(b'A' * 0x10))
+
+    def test_int_memoryview(self):
+        self.assertEqual(int(memoryview(b'123')[1:3]), 23)
+        self.assertEqual(int(memoryview(b'123\x00')[1:3]), 23)
+        self.assertEqual(int(memoryview(b'123 ')[1:3]), 23)
+        self.assertEqual(int(memoryview(b'123A')[1:3]), 23)
+        self.assertEqual(int(memoryview(b'1234')[1:3]), 23)
+
+    def test_string_float(self):
+        self.assertRaises(ValueError, int, '1.2')
+
+    def test_intconversion(self):
+        # Test __int__()
+        class ClassicMissingMethods:
+            pass
+        self.assertRaises(TypeError, int, ClassicMissingMethods())
+
+        class MissingMethods(object):
+            pass
+        self.assertRaises(TypeError, int, MissingMethods())
+
+        class Foo0:
+            def __int__(self):
+                return 42
+
+        self.assertEqual(int(Foo0()), 42)
+
+        class Classic:
+            pass
+        for base in (object, Classic):
+            class IntOverridesTrunc(base):
+                def __int__(self):
+                    return 42
+                def __trunc__(self):
+                    return -12
+            self.assertEqual(int(IntOverridesTrunc()), 42)
+
+            class JustTrunc(base):
+                def __trunc__(self):
+                    return 42
+            self.assertEqual(int(JustTrunc()), 42)
+
+            class ExceptionalTrunc(base):
+                def __trunc__(self):
+                    1 / 0
+            with self.assertRaises(ZeroDivisionError):
+                int(ExceptionalTrunc())
+
+            for trunc_result_base in (object, Classic):
+                class Integral(trunc_result_base):
+                    def __int__(self):
+                        return 42
+
+                class TruncReturnsNonInt(base):
+                    def __trunc__(self):
+                        return Integral()
+                with self.assertWarns(DeprecationWarning):
+                    self.assertEqual(int(TruncReturnsNonInt()), 42)
+
+                class NonIntegral(trunc_result_base):
+                    def __trunc__(self):
+                        # Check that we avoid infinite recursion.
+                        return NonIntegral()
+
+                class TruncReturnsNonIntegral(base):
+                    def __trunc__(self):
+                        return NonIntegral()
+                try:
+                    int(TruncReturnsNonIntegral())
+                except TypeError as e:
+                    self.assertEqual(str(e),
+                                      "__trunc__ returned non-Integral"
+                                      " (type NonIntegral)")
+                else:
+                    self.fail("Failed to raise TypeError with %s" %
+                              ((base, trunc_result_base),))
+
+                # Regression test for bugs.python.org/issue16060.
+                class BadInt(trunc_result_base):
+                    def __int__(self):
+                        return 42.0
+
+                class TruncReturnsBadInt(base):
+                    def __trunc__(self):
+                        return BadInt()
+
+                with self.assertRaises(TypeError):
+                    int(TruncReturnsBadInt())
+
+    def test_int_subclass_with_int(self):
+        class MyInt(int):
+            def __int__(self):
+                return 42
+
+        class BadInt(int):
+            def __int__(self):
+                return 42.0
+
+        my_int = MyInt(7)
+        self.assertEqual(my_int, 7)
+        self.assertEqual(int(my_int), 42)
+
+        self.assertRaises(TypeError, int, BadInt())
+
+    def test_int_returns_int_subclass(self):
+        class BadInt:
+            def __int__(self):
+                return True
+
+        class BadInt2(int):
+            def __int__(self):
+                return True
+
+        class TruncReturnsBadInt:
+            def __trunc__(self):
+                return BadInt()
+
+        class TruncReturnsIntSubclass:
+            def __trunc__(self):
+                return True
+
+        bad_int = BadInt()
+        with self.assertWarns(DeprecationWarning):
+            n = int(bad_int)
+        self.assertEqual(n, 1)
+        self.assertIs(type(n), int)
+
+        bad_int = BadInt2()
+        with self.assertWarns(DeprecationWarning):
+            n = int(bad_int)
+        self.assertEqual(n, 1)
+        self.assertIs(type(n), int)
+
+        bad_int = TruncReturnsBadInt()
+        with self.assertWarns(DeprecationWarning):
+            n = int(bad_int)
+        self.assertEqual(n, 1)
+        self.assertIs(type(n), int)
+
+        good_int = TruncReturnsIntSubclass()
+        n = int(good_int)
+        self.assertEqual(n, 1)
+        self.assertIs(type(n), int)
+        n = IntSubclass(good_int)
+        self.assertEqual(n, 1)
+        self.assertIs(type(n), IntSubclass)
+
+    def test_error_message(self):
+        def check(s, base=None):
+            with self.assertRaises(ValueError,
+                                   msg="int(%r, %r)" % (s, base)) as cm:
+                if base is None:
+                    int(s)
+                else:
+                    int(s, base)
+            self.assertEqual(cm.exception.args[0],
+                "invalid literal for int() with base %d: %r" %
+                (10 if base is None else base, s))
+
+        check('\xbd')
+        check('123\xbd')
+        check('  123 456  ')
+
+        check('123\x00')
+        # SF bug 1545497: embedded NULs were not detected with explicit base
+        check('123\x00', 10)
+        check('123\x00 245', 20)
+        check('123\x00 245', 16)
+        check('123\x00245', 20)
+        check('123\x00245', 16)
+        # byte string with embedded NUL
+        check(b'123\x00')
+        check(b'123\x00', 10)
+        # non-UTF-8 byte string
+        check(b'123\xbd')
+        check(b'123\xbd', 10)
+        # lone surrogate in Unicode string
+        check('123\ud800')
+        check('123\ud800', 10)
+
+    def test_issue31619(self):
+        self.assertEqual(int('1_0_1_0_1_0_1_0_1_0_1_0_1_0_1_0_1_0_1_0_1_0_1_0_1_0_1_0_1_0_1', 2),
+                         0b1010101010101010101010101010101)
+        self.assertEqual(int('1_2_3_4_5_6_7_0_1_2_3', 8), 0o12345670123)
+        self.assertEqual(int('1_2_3_4_5_6_7_8_9', 16), 0x123456789)
+        self.assertEqual(int('1_2_3_4_5_6_7', 32), 1144132807)
+
+
+if __name__ == "__main__":
+    unittest.main()