How does KPSSTEST function actually work?

Hi all, I'm using the built-in MATLAB function kpsstest to do stationary test for an input sequence, but I find the output is not as expected. I paste the results as bellow. My questions are: (1) why x = [1 1] is rejected while x = [1 1 1] is accepted? (2) why x = ones(1, 10^6) is rejected while x = zeros(1, 10^6) is accepted?

>> x = [0 0]; >> kpsstest(x, 'alpha', .01, 'trend', false)

ans =

     0

>> x = [0 1]; >> kpsstest(x, 'alpha', .01, 'trend', false)

ans =

     0

>> x = [1 0]; >> kpsstest(x, 'alpha', .01, 'trend', false)

ans =

     0

>> x = [1 1]; >> kpsstest(x, 'alpha', .01, 'trend', false)

*ans =

     1*

>> x = [1 1 1]; >> kpsstest(x, 'alpha', .01, 'trend', false)

ans =

     0

>> x = [1 1 1 1]; >> kpsstest(x, 'alpha', .01, 'trend', false)

ans =

     0

>> x = ones(1, 10^6); >> kpsstest(x, 'alpha', .01, 'trend', false)

*ans =

     1*

>> x = zeros(1, 10^6); >> kpsstest(x, 'alpha', .01, 'trend', false)

ans =

     0