import sys, os
sys.path.insert(0, os.path.dirname(__file__))
from min_window_substring import min_window

def test_basic():
    assert min_window("ADOBECODEBANC", "ABC") == "BANC"
def test_a():
    assert min_window("a", "a") == "a"
def test_no():
    assert min_window("a", "aa") == ""
def test_empty_t():
    assert min_window("abc", "") == ""
def test_empty_s():
    assert min_window("", "a") == ""
def test_dup_t():
    assert min_window("aa", "aa") == "aa"
def test_unicode():
    assert min_window("a\u00e9b\u00e9c", "\u00e9\u00e9") == "\u00e9b\u00e9"
def test_single_char_missing():
    assert min_window("abc", "d") == ""