The Linear Complexity test determines whether or not the sequence is complex enough to be considered random. A short feedback register implies non-randomness. The cumulative sum may be considered as a random walk. For a random sequence, the random walk should oscillate around zero. Large values of the walk indicate too many zeros or ones near the start of the sequence.
Small values indicate that the zeros and ones are intermixed too evenly.
The Random Excursions Variant test extends the Random Excursions test by examining level crossing distributions across multiple excursions between zero level crossings. The source code for the tests was developed in ANSI C on a SUN workstation running under the Solaris operating system. Other systems may require modifications to the source code to run properly. Instructions are provided in NIST SP 800-22 for installing, modifying, and operating the test code and interpreting the results. Sample generators are provided along with the test code that can be used to run with the tests and compare against the expected results that are provided in the document.