change stream creation function names
refactor Buffer object encoding and decoding tests

* add a setUp function to initialize the testing environment
* add a tearDown function to clean the testing environment
* add a test vector with the reference samples
* extract internal test scopes into a function that sweeps the entire test vector
* create specific assert callback for each test case
finish stream encoding and decoding tests

* refactor stream encoding test
* add code to the stream decoding test
* rename some assertion descriptions