Eio_mock.FlowSourceMock Eio.Flow sources and sinks.
make label is a mock Eio flow. It can be used as a source, sink, or two-way flow.
on_read t actions configures the values to return from the mock's read function.
on_copy_bytes t actions configures the number of bytes to copy in each iteration.
set_copy_method t m configures t to use the given method to read from a source during a copy operation.