added in description

Where?

Why in the first case sun comes bebore sat and in the second case sat comes before sun?

This example is from the description:

Input: [0, 1, 0, 0, 1, 1, 0]

Output: "mon, thu and Fri"

If we are supposed to put "close" days first, then why is the output "mon, thu and Fri" but not "thu, fri and mon"?

Borrowed this example from anter69:

Input: [1, 0, 0, 1, 1, 0, 1]: 'sun, wed, thu and sat' should equal 'sat, sun, wed and thu'

I think this case needs more clarification.

There are two pairs of "close" days. So what makes the answer "sat, sun, wed and thu" but not "wed, thu, sat and sun"?

added in description

You could now remove all other random tests, as they are redundant

Minor question: why 448 tests, when only 127 combinations? :-)

test_cases = []
for n in range(1, 128):
    test_cases.append(list(map(int, f"{n:07b}")))

This is still there:

Output: "mon, thu and Fri"

Inconsistent results:

[1, 0, 0, 0, 0, 0, 1] -> sun and sat
[1, 0, 1, 0, 0, 0, 1] -> sat, sun and tue

fixed the description

removed

test case added

add the statement in instruction

Input: [0, 0, 1, 1, 1, 0, 1]: 'tue to thu and sat' should equal 'sat and tue to thu'
Input: [1, 0, 0, 1, 1, 0, 1]: 'sun, wed, thu and sat' should equal 'sat, sun, wed and thu'
etc

Why?

As there is a limited number of possible inputs (127), all of them should be tested, in random order - that should replace the current random tests

Description:

The input list days will always have a length of 7.

Sample tests:

test.assert_equals(custom([]), '')    # len([]) != 7

#1:

If an alarm is scheduled for consecutive days, the output should indicate a range (e.g., "Mon to Wed").

vs

Input: [1, 1, 0, 1, 0, 0, 0]

Output: "sun, mon and wed"

Either fix the description ("at least 3 consecutive days") or fix the example ("sun to mon and wed")

#2:

output sholud be in lower case

vs

Output: "mon, thu and _F_ri"

output should indicate a range (e.g., "_M_on to _W_ed")