buffer size test: copy text with 1 buffer size, ignore requests to shrink
abcdef
actual read/write buffer sizes: 1/1

buffer size test: copy text with 2 buffer size, ignore requests to shrink
ghijkl
actual read/write buffer sizes: 2/2

buffer size test: copy text with 1 buffer size, ignore requests to shrink
mnopqr
actual read/write buffer sizes: 2/2

formatting test: print a number
1234567890

memory stream test prep: prefill the VSTRING
VSTRING content length: 8/8, content: 01234567

memory stream test: open the VSTRING for writing, overwrite, close
initial memory VSTREAM write offset: 0/8
final memory VSTREAM write offset: 5/8
VSTRING content length: 5/8, content: hallo

memory stream test: open the VSTRING for append, write multiple, then overwrite 1
initial memory VSTREAM write offset: 5/8
final memory VSTREAM write offset: 11/16
VSTRING content length: 11/16, content: hallo world

replace second character and close
VSTRING content length: 11/16, content: hello world

memory stream test: open VSTRING for reading, then read
initial memory VSTREAM read offset: 0/11
reading memory VSTREAM: hello world
final memory VSTREAM read offset: 11/11
seeking to offset 12 should work: PASS
VSTREAM_GETC should return VSTREAM_EOF
PASS
final memory VSTREAM read offset: 12/11
VSTRING content length: 11/16, content: hello world