import math
# 6A: This function fails its positive-count contract. Record expected/actual
# results, find a smaller failing input and trace count before proposing a fix.
def count_active(values):
    for value in values:
        count = 0
        if value > 0:
            count += 1
    return count
# 6B: Implement a mean with an explicit ValueError for empty input.
def mean_minutes(values):
    raise NotImplementedError("Write your solution")
# Add ordinary, single-value, zero-only and empty-input tests for 6A and 6B.
# 6C: Use math.isclose to check 0.1 + 0.2 against 0.3 with a tight tolerance,
# and prove that 0.31 is NOT close to 0.3 at that tolerance.
# Explain what each test guards. Do not catch every error.
assert count_active([10, 0, 20]) == 2
assert count_active([]) == 0
assert math.isclose(mean_minutes([10, 20, 30]), 20)