I don't think it's a great idea to hide the test cases, especially if it turns out that the test cases are wrong. Aside from that, hiding the test cases is an act that totally contradicts a TDD approach. The TDD approach is, of course, based on total disclosure of what the tests are about.

I got "10 should equal 9" on Test #5 when I submitted my run.

This is because assertion #5 is wrong. It should say

test.assert_equals(levenshtein("nayvyedosf","sjxen"), 10)

and absolutely not

test.assert_equals(levenshtein("nayvyedosf","sjxen"), 9)

I opened Firefox :)

This algorithm ("get the equation of a line from a sequence") passed the tests. However, the submission failed with an "unknown error":

def get_function(sequence):
    slope = sequence[1] - sequence[0]
    intercept = sequence[0]
    if slope == 0:
        return 'f(x) = '+str(intercept)
    elif (slope == 1)and(intercept == 0):
        return 'f(x) = x'
    elif intercept == 0:
        return 'f(x) = '+str(slope)+'x'
    else:
        return 'f(x) = '+str(slope)+'x'+ ' + '+str(intercept)