def test_is_empty():
s = String(["f", 's', ' '])
rez = s.is_empty()
assert False == rez
s1 = String([])
rez1 = s1.is_empty()
assert True == rez1
def test_len():
s = String(['u', 'n', 'o'])
result = s.length()
assert 3 == result
def test_concat():
s = String(['u', 'n', 'o'])
st = ['d', 'o', 'u', 's']
s.concat(st)
assert ['u', 'n', 'o', 'd', 'o', 'u', 's'] == s.list
def test_double():
s = String(['u', 'n', 'o'])
result = s.double(2)
assert ['u', 'n', 'o', 'u', 'n', 'o'] == result
def test_f():
s = String(['u', 'n', 'n', 'o'])
result = s.f('n')
result1 = s.f('l')
assert 1 == result
assert -1 == result1
def test_rf():
s = String(['u', 'o', 'n', 'o'])
result = s.rf('o')
result1 = s.rf('l')
assert 3 == result
assert -1 == result1
def test_slovo():
s = String(['u', 'n', 'o'])
result = s.is_slovo('no')
result1 = s.is_slovo('kkk')
assert True == result
assert False == result1
def test_big():
s = String(['u', 'G'])
result = s.big()
assert ['U', 'G'] == result
def test_small():
s = String(['u', 'G'])
result = s.small()
assert ['u', 'g'] == result
def test_space():
s = String([' ', 'u', 'g', ' '])
result = s.space()
assert ['u', 'g'] == result