hust_test/*: use "$THIS_SH" instead of hush

diff --git a/shell/hush_test/hush-vars/var3.tests b/shell/hush_test/hush-vars/var3.tests
index 2947fcc..e09f433 100755
--- a/shell/hush_test/hush-vars/var3.tests
+++ b/shell/hush_test/hush-vars/var3.tests
@@ -1,4 +1,4 @@
 # reject invalid vars
-hush -c 'echo ${1q}'
-hush -c 'echo ${&}'
-hush -c 'echo ${$}'
+"$THIS_SH" -c 'echo ${1q}'
+"$THIS_SH" -c 'echo ${&}'
+"$THIS_SH" -c 'echo ${$}'