Some missing tests:
0) g/./s^@^@	- okay: NULs in commands
1) g/./s/^@/	- okay: NULs in patterns
2) a
   hello^V^Jworld	
   .		- okay: embedded newlines in insert mode
3) ed -x 	- verify: 8-bit clean
4) ed		- verify: long-line support
5) ed		- verify: interactive/help mode
6) G/pat/	- verify: global interactive command
7) V/pat/	- verify: global interactive command