First of all, reading unformatted code is really difficult. You really need to use code formatting when showing solution.

The next thing is, your problem is when missing num is 100. Try this assertion and see:

test.assert_equals(missing_no(list(range(100))), 100)

It is difficult to find problems in your solution without knowing what your solution is.

If the solution I see is your most recent one, it seems that indeed, it does not handle the case when the missing number is 100. I think you did some mistake when checking what input fails.

Anyway, your solution is buggy, it is not a kata issue.

Sorry, no errors in the tests.