[test] binary-nested-in-map: move fixture creation into %test:setUp

Per review feedback on PR #6507: the fixture setup (create the test directory and
write the .env fixture) now lives in a %test:setUp function, symmetric with the
existing %test:tearDown, instead of inline in the test body.

helper:get-test-directory embeds a fresh uuid on every call, so the directory is
computed once in a module variable ($bnm:directory) shared by setUp and the test,
rather than recomputed per function (which would land the fixture and the read in
different directories).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: joewiz

extensions/modules/file/src/test/xquery/modules/file/binary-nested-in-map.xqm

@@ -41,6 +41,17 @@ declare namespace test="http://exist-db.org/xquery/xqsuite";
 
 declare variable $bnm:suite := "binary-nested-in-map";
 
+(: One directory per run, shared by setUp and the test (helper:get-test-directory embeds a fresh uuid
+ : on each call, so it must be computed once here rather than recomputed in each function). :)
+declare variable $bnm:directory := helper:get-test-directory($bnm:suite);
+
+declare
+    %test:setUp
+function bnm:set-up() as empty-sequence() {
+    let $_ := helper:setup-fs-extra($bnm:directory)
+    return ()
+};
+
 declare
     %test:tearDown
 function bnm:tear-down() as empty-sequence() {
@@ -61,7 +72,5 @@ function bnm:make-nested($path as xs:string) {
 declare
     %test:assertEquals("SERVER_SECRET=123!")
 function bnm:binary-nested-in-map-survives-function-return() {
-    let $directory := helper:get-test-directory($bnm:suite)
-    let $_ := helper:setup-fs-extra($directory)
-    return util:binary-to-string(bnm:make-nested(concat($directory, "/.env"))[1]?data)
+    util:binary-to-string(bnm:make-nested(concat($bnm:directory, "/.env"))[1]?data)
 };