to what the shell produces for tilde expansions, when the expansion
of the tilde prefix ends with '/' and the character immediately following
is another '/' - previously /bin/sh (and most other shells, but not all)
retained both slashes, and this test expected that behaviour.
No longer, now only one of the two will appear. Adjust the expected
test results accordingly, and add an extra loop iteration to make sure
this is thoroughly tested (one more tilde expansion value).
Also, add two new test cases that test for the new (explicit - though
it was always stated this way, but not as explicitly) that if HOME is
an empty string (not unset - that remains an unspecified case, as it
was) then the expansion of ~ must generate "", and not nothing.
The current test was unable to distinguish those two, since it
simply looked for characters in the output, so add a new test cases
explicitly to test for this particular case. This also means (also
previously in the standard, but not as explicitly) that shells are
not permitted to decide "The ~ expansion produces an empty string, that
is weird, let's generate something else instead" which some shells were
doing.