Create an element using the factory providing the element_name and push the buffer_in to this element.
The element should create one buffer and this will be compared with buffer_out. We only check the caps and the data of the
buffers. This function unrefs the buffers.
| element_name |
name of the element that needs to be created |
| buffer_in |
push this buffer to the element |
| caps_in |
the Caps expected of the sinkpad of the element |
| buffer_out |
compare the result with this buffer |
| caps_out |
the Caps expected of the srcpad of the element |