Create an element using the factory providing the element_name and push the buffers in buffer_in to this
element.
The element should create the buffers equal to the buffers in buffer_out. We only check the size and the data of the
buffers. This function unrefs the buffers in the two lists. The last_flow_return parameter indicates the expected flow return value from
pushing the final buffer in the list. This can be used to set up a test which pushes some buffers and then an invalid buffer, when the
final buffer is expected to fail, for example.
| element_name |
name of the element that needs to be created |
| buffer_in |
a list of buffers that needs to be pushed to the element |
| caps_in |
the Caps expected of the sinkpad of the element |
| buffer_out |
a list of buffers that we expect from the element |
| caps_out |
the Caps expected of the srcpad of the element |
| last_flow_return |
the last buffer push needs to give this GstFlowReturn |