def test_isint_returns_False_for_strings(x):
    assert not isint(x)
def test_isint_returns_True_for_real_numbers(x):
    assert isint(x)
def test_isint_returns_False_for_strings_example():
    assert not isint('45')
    assert not isint('invalid')
def test_isint_returns_True_for_real_numbers_example():
    assert isint(-45)
    assert isint(45)
def test_isint_returns_False_for_strings(x):
    assert not isint(x)
def test_isint_returns_False_for_strings_example():
    assert not isint('45')
    assert not isint('invalid')
def test_isint_returns_True_for_real_numbers(x):
    assert isint(x)
def test_isint_returns_True_for_real_numbers_example():
    assert isint(-45)
    assert isint(45)