The langage used by behave is Gherkin: the same langage as cucumber:

https://github.com/cucumber/cucumber/wiki/Gherkin

The behave documentation:

http://pythonhosted.org/behave/

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A few tips:

The test code should be in the folder features/steps in a file named steps_*.py

* "Given" are used for initial conditions.
* "When" are actions actually performed with the software or a third party
application
* "Then" is used to check if teh actions performed actually resulted in the
expected results. Therefor, it should always contain at least one "assert"

When checking the result of "videostitch-cmd" always delete the output file,
it will avoid false positive