How to run another shell and have all current shell dectaration copied to that new shell?

I would like to have available all current declarations in a new shell. That are functions, aliases, variables.

I need to test some functions that use the 'exit', but running it in current shell on 'exit' will close the shell, which I do not like.

# export thing=hello
# echo $thing
hello
# bash
# echo $thing
hello
#

I had a similar issue recently and found that I could use the "return" command and it wouldn't kill my session.
ex:
return 10

This is under ksh.

The problem is:
The only EXPORTED variables are copyed.
I need many functions and declared not exported variables.
I am running functions which change and define variables.
Some of them need to be run in separate process, in '()': like >(funct_boo)
I do not want redeclare all functions, aliases and variables in the new process

src> alias boo="echo boo-boo"
src> foo()
> {
> echo "foo from func";
> }
src> foo
foo from func
src> boo
boo-boo
src> var=variable
src> echo $var
variable
src> hm
dca0701> bash
executing file .bashrc - starting the bash shell--
----> Start of the .myset file  <---
----> End   of the .myset file  <---
src> foo
bash: foo: command not found
src> boo
bash: boo: command not found
src> echo $var

src>

Still have no idea how to do it.
Is it possible to run another shell and have all FUNCTIONS and ALIASES from current shell be available in new one?

bash has an -a option to automatically export all variables and functions, dunno if this is a bashism but I would guess it's POSIX. Try "set -a" at the top of the script.

In bash, it seems you can't export aliases. All the more reason to use functions instead of aliases.