builtins: test: Fix a = b.

check.sh

@@ -124,6 +124,7 @@ tests='
 100-cd
 100-cd-foo
 
+100-test
 100-test-file
 100-bracket-file
 

gash/builtins.scm

@@ -298,10 +298,11 @@ Options:
 "))
                (version? (format #t "test (GASH) ~a\n" %version))
                ((null? files) #f)
-               ((or (option-ref options 'n #f)
-                    no-options?)
+               ((or (option-ref options 'string-not-null #f)
+                    (and no-options?
+                         (= (length files) 1)))
                 (not (string-null? file)))
-               ((option-ref options 'z #f)
+               ((option-ref options 'string-null #f)
                 (string-null? file))
                ((and (= (length files) 3)
                      (member (cadr files) '("=" "==")))

test/100-test.sh

@@ -0,0 +1,3 @@
+if test a = b; then
+    exit 1;
+fi