diff --git a/crates/trusted-server-core/src/tsjs.rs b/crates/trusted-server-core/src/tsjs.rs
index 4921a9bb..773503fc 100644
--- a/crates/trusted-server-core/src/tsjs.rs
+++ b/crates/trusted-server-core/src/tsjs.rs
@@ -64,3 +64,105 @@ pub fn tsjs_deferred_script_tags(module_ids: &[&str]) -> String {
         .map(|id| tsjs_deferred_script_tag(id))
         .collect::<String>()
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const UNIFIED_SCRIPT_PREFIX: &str = "/static/tsjs=tsjs-unified.min.js?v=";
+
+    fn assert_sha256_hex(hash: &str) {
+        assert_eq!(hash.len(), 64, "should include a SHA-256 hex hash");
+        assert!(
+            hash.chars()
+                .all(|character| matches!(character, '0'..='9' | 'a'..='f')),
+            "should include only lowercase hex characters"
+        );
+    }
+
+    #[test]
+    fn tsjs_script_src_includes_stable_cache_busting_hash() {
+        let module_ids = ["core", "lockr", "permutive"];
+
+        let src = tsjs_script_src(&module_ids);
+        let hash = src
+            .strip_prefix(UNIFIED_SCRIPT_PREFIX)
+            .expect("should include unified script URL prefix");
+
+        assert_sha256_hex(hash);
+        assert_eq!(
+            src,
+            tsjs_script_src(&module_ids),
+            "should produce a stable URL for identical module IDs"
+        );
+    }
+
+    #[test]
+    fn tsjs_script_tag_uses_generated_src_and_trusted_server_id() {
+        let module_ids = ["core", "lockr"];
+        let src = tsjs_script_src(&module_ids);
+        let tag = tsjs_script_tag(&module_ids);
+
+        assert_eq!(
+            tag.matches("<script").count(),
+            1,
+            "should emit one opening script tag"
+        );
+        assert_eq!(
+            tag.matches("</script>").count(),
+            1,
+            "should emit one closing script tag"
+        );
+        assert!(
+            tag.contains(r#"id="trustedserver-js""#),
+            "should include trusted server script ID"
+        );
+        assert_eq!(
+            tag,
+            format!(r#"<script src="{src}" id="trustedserver-js"></script>"#),
+            "should use generated script source"
+        );
+    }
+
+    #[test]
+    fn tsjs_deferred_script_src_includes_module_cache_busting_hash() {
+        let src = tsjs_deferred_script_src("prebid");
+        let hash = src
+            .strip_prefix("/static/tsjs=tsjs-prebid.min.js?v=")
+            .expect("should include deferred script URL prefix");
+
+        assert_sha256_hex(hash);
+    }
+
+    #[test]
+    fn tsjs_deferred_script_tag_uses_generated_src_and_defer() {
+        let src = tsjs_deferred_script_src("prebid");
+        let tag = tsjs_deferred_script_tag("prebid");
+
+        assert_eq!(
+            tag,
+            format!(r#"<script src="{src}" defer></script>"#),
+            "should use generated deferred script source"
+        );
+    }
+
+    #[test]
+    fn tsjs_deferred_script_tags_concatenates_tags_in_order() {
+        let module_ids = ["prebid", "lockr"];
+
+        assert_eq!(
+            tsjs_deferred_script_tags(&module_ids),
+            format!(
+                "{}{}",
+                tsjs_deferred_script_tag("prebid"),
+                tsjs_deferred_script_tag("lockr")
+            ),
+            "should concatenate deferred script tags in module order"
+        );
+        assert_eq!(
+            tsjs_deferred_script_tags(&[]),
+            "",
+            "should return empty output for no deferred modules"
+        );
+    }
+}