diff --git a/testing/btest/Baseline/javascript.file-sniff/files.log.cut b/testing/btest/Baseline/javascript.file-sniff/files.log.cut
new file mode 100644
index 0000000000..fb62c5def5
--- /dev/null
+++ b/testing/btest/Baseline/javascript.file-sniff/files.log.cut
@@ -0,0 +1,3 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+fuid	uid	from_js
+FMnxxt3xjVcWNS2141	CHhAvVGS1DHFjwGM9	Hello from JavaScript
diff --git a/testing/btest/Baseline/javascript.file-sniff/out b/testing/btest/Baseline/javascript.file-sniff/out
new file mode 100644
index 0000000000..4d5945a08b
--- /dev/null
+++ b/testing/btest/Baseline/javascript.file-sniff/out
@@ -0,0 +1,3 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+file_sniff FMnxxt3xjVcWNS2141 {"mime_type":"text/plain","mime_types":[{"strength":-20,"mime":"text/plain"}],"inferred":true}
+file_state_remove FMnxxt3xjVcWNS2141
diff --git a/testing/btest/javascript/file-sniff.js b/testing/btest/javascript/file-sniff.js
new file mode 100644
index 0000000000..81d90fd862
--- /dev/null
+++ b/testing/btest/javascript/file-sniff.js
@@ -0,0 +1,22 @@
+/*
+ * @TEST-REQUIRES: $SCRIPTS/have-javascript
+ * @TEST-EXEC: zeek -b -Cr $TRACES/http/get.trace base/protocols/http ./ext.zeek %INPUT > out
+ * @TEST-EXEC: zeek-cut -m fuid uid from_js < files.log > files.log.cut
+ * @TEST-EXEC: btest-diff out
+ * @TEST-EXEC: btest-diff files.log.cut
+ */
+
+zeek.on('file_sniff', (f, meta) => {
+  console.log(`file_sniff ${f.id} ${JSON.stringify(meta)}`);
+});
+
+zeek.on('file_state_remove', (f) => {
+  console.log(`file_state_remove ${f.id}`);
+  f.info.from_js = "Hello from JavaScript";
+});
+
+@TEST-START-FILE ext.zeek
+redef record Files::Info += {
+  from_js: string &log &optional;
+};
+@TEST-END-FILE