feat: Update Makefile

Makefile

@@ -19,7 +19,7 @@ help:
 
 tests:
 	# See bats(1), https://bats-core.readthedocs.io/en/latest/index.html
-	for test in $(tests_dir)/*.bats; do bats --verbose-run --print-output-on-failure "$$@" "$$test"; done
+	for test in $(tests_dir)/*.bats; do bats --verbose-run --print-output-on-failure "$$test"; done
 
 docs: builddir
 	# See rst2man(1), rst2html(1), https://docutils.sourceforge.io/docs/index.html