def test_count_substring_none():
test_string = "AGTCCCCTAGA"
test_substring = "AAA"
expected_count = 0
observed_count = count_substring(test_string, test_substring)
assert expected_count == observed_count
def test_count_substring_single():
test_string = "CGCTAGCGT"
test_substring = "TAG"
expected_count = 1
observed_count = count_substring(test_string, test_substring)
assert expected_count == observed_count
def test_count_substring_repeated():
test_string = "AGCTAGCAGT"
test_substring = "AGC"
expected_count = 2
observed_count = count_substring(test_string, test_substring)
assert expected_count == observed_count
def test_count_substring_none_case_insensitive2():
test_string = "agtcccctaga"
test_substring = "AAA"
expected_count = 0
observed_count = count_substring(test_string, test_substring)
assert expected_count == observed_count
def test_count_substring_none_case_insensitive1():
test_string = "AGTCcCCTAGA"
test_substring = "AAA"
expected_count = 0
observed_count = count_substring(test_string, test_substring)
assert expected_count == observed_count
def test_count_substring_repeated_case_insensitive3():
test_string = "AGCtAGCAGT"
test_substring = "AGC"
expected_count = 2
observed_count = count_substring(test_string, test_substring)
assert expected_count == observed_count
def test_count_substring_single_case_insensitive3():
test_string = "CGCTaGCgT"
test_substring = "TAG"
expected_count = 1
observed_count = count_substring(test_string, test_substring)
assert expected_count == observed_count