Sojourn time tests are applied to m-sequences with characteristic primitive pen tanomials. Some of the tested m-sequences with characteristic pentanomials are evidently rejected by the sojourn time tests, but their graphs of simulation do not show explicit gaps. This makes clear contrast with the case of m-sequences with characteristic trinomials, which showed explicit graphical gaps. We further propose a combination of chi-square test and Kolmogorov Smirnov test.