Add tests for support of binomial distribution

[devmotion]

#125 fixed #115. This PR just adds some tests.

[codecov-commenter]

Codecov Report

Merging #127 (a1560c4) into master (53e8888) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #127   +/-   ##
=======================================
  Coverage   37.41%   37.41%           
=======================================
  Files          12       12           
  Lines         417      417           
=======================================
  Hits          156      156           
  Misses        261      261           

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