bashunit assert with a missing argument leaks a bash error and exits 0

[Chemaclass]

🤔 Background

The standalone assert subcommand does not check that it received enough arguments before indexing the argument array.

local last_index=$((args_count - 1))
local last_arg="${args[$last_index]}"

With no arguments after the assertion name, args_count is 0, so last_index is -1. Bash 3.x has no negative array subscripts, so the expansion fails — and the run continues and exits 0:

$ ./bashunit assert equals
./src/main.sh: line 1182: args: bad array subscript
$ echo $?
0

A malformed standalone assertion reports success. docs/standalone.md presents this subcommand for integration and end-to-end checks, so a mistyped invocation in a deploy script passes silently.

Working cases, for contrast

The rest of the subcommand handles errors well — this is the one gap:

Invocation	Result
assert equals foo foo	exit 0
assert equals foo bar	exit 1, ✗ Failed: assert equals
assert no_such_assertion foo foo	exit 127, Function no_such_assertion does not exist.
assert equals	exit 0, bad array subscript

Suggested fix

Reject an argument count below what the assertion needs with a clear message and a non-zero exit, in the same style as the existing "Function ... does not exist." path. Note the negative-subscript expansion is also a Bash 3.0 compatibility violation per .claude/rules/bash-style.md.