def test_single4(self):
linq = Linq([1, 1, 2, 3, 5])
assert_equal(linq.single(cond_f=lambda x: x % 2 == 0), 2)
def test_single2(self):
linq = Linq([])
linq.single()
def test_single3(self):
linq = Linq([1, 2])
linq.single()
def test_single(self):
linq = Linq([1])
assert_equal(linq.single(), 1)
assert_equal(linq.single(), 1)
