diff --git a/crates/engine/src/lib.rs b/crates/engine/src/lib.rs
index 34653bd5..8609fb21 100644
--- a/crates/engine/src/lib.rs
+++ b/crates/engine/src/lib.rs
@@ -1710,6 +1710,8 @@ mod vector_behaviour_tests;
 #[cfg(test)]
 mod vector_multi_behaviour_tests;
 #[cfg(test)]
+mod vector_offset_tests;
+#[cfg(test)]
 mod version_preview_tests;
 #[cfg(test)]
 mod version_tests;
diff --git a/crates/engine/src/tests.rs b/crates/engine/src/tests.rs
index 746f417e..dbf432d4 100644
--- a/crates/engine/src/tests.rs
+++ b/crates/engine/src/tests.rs
@@ -621,41 +621,3 @@ fn find_replace_changing_only_the_case_replaces_every_occurrence() {
     assert_eq!(s.doc().unwrap().node(t).unwrap().kind.text().unwrap().characters, "FigCraft and FigCraft, FigCraft");
     assert_eq!(s.doc().unwrap().node(f).unwrap().name, "FigCraft / FigCraft");
 }
-
-/// No node that holds children may be a non-container.
-fn assert_children_only_in_containers(s: &Session, ids: &[NodeId]) {
-    let doc = s.doc().unwrap();
-    for &i in ids {
-        let n = doc.node(i).unwrap();
-        assert!(n.kind.is_container() || n.kind.is_frame_like() || n.children.is_empty(), "a non-container layer now holds children");
-    }
-}
-
-#[test]
-fn offset_path_leaves_containers_with_children_alone() {
-    let mut s = sess();
-    let f = id(&s.execute("frame.create", &json!({"x": 0, "y": 0, "width": 100, "height": 100})).unwrap());
-    let inner = id(&s.execute("shape.rectangle", &json!({"x": 10, "y": 10, "width": 10, "height": 10, "parent": f})).unwrap());
-    let a = id(&s.execute("shape.rectangle", &json!({"x": 200, "y": 0, "width": 10, "height": 10})).unwrap());
-    let b = id(&s.execute("shape.rectangle", &json!({"x": 220, "y": 0, "width": 10, "height": 10})).unwrap());
-    let g = id(&s.execute("object.group", &json!({"ids": [a, b]})).unwrap());
-    for target in [f, g] {
-        s.execute("vector.offset", &json!({"ids": [target], "offset": 5})).unwrap();
-        assert_children_only_in_containers(&s, &[f, g, inner, a, b]);
-    }
-    let doc = s.doc().unwrap();
-    assert!(doc.node(f).unwrap().kind.is_container());
-    assert_eq!(doc.node(f).unwrap().children, vec![inner]);
-    assert!(doc.node(g).unwrap().kind.is_container());
-    assert_eq!(doc.node(g).unwrap().children.len(), 2);
-}
-
-#[test]
-fn offset_path_still_converts_a_plain_rectangle() {
-    let mut s = sess();
-    let r = id(&s.execute("shape.rectangle", &json!({"x": 0, "y": 0, "width": 10, "height": 10})).unwrap());
-    s.execute("vector.offset", &json!({"ids": [r], "offset": 5})).unwrap();
-    let n = s.doc().unwrap().node(r).unwrap().clone();
-    assert!(matches!(n.kind, NodeKind::Vector { .. }));
-    assert!(n.width > 10.0);
-}
diff --git a/crates/engine/src/vector_offset_tests.rs b/crates/engine/src/vector_offset_tests.rs
new file mode 100644
index 00000000..e47158f2
--- /dev/null
+++ b/crates/engine/src/vector_offset_tests.rs
@@ -0,0 +1,49 @@
+//! `vector.offset` on layers with children: containers are left alone.
+
+use serde_json::{Value, json};
+
+use crate::Session;
+use crate::params::id_of;
+use figcraft_doc::{NodeId, NodeKind};
+
+fn id(v: &Value) -> NodeId {
+    id_of(&v["id"]).unwrap()
+}
+
+/// No node that holds children may be a non-container.
+fn assert_children_only_in_containers(s: &Session, ids: &[NodeId]) {
+    let doc = s.doc().unwrap();
+    for &i in ids {
+        let n = doc.node(i).unwrap();
+        assert!(n.kind.is_container() || n.kind.is_frame_like() || n.children.is_empty(), "a non-container layer now holds children");
+    }
+}
+
+#[test]
+fn offset_path_leaves_containers_with_children_alone() {
+    let mut s = Session::new();
+    let f = id(&s.execute("frame.create", &json!({"x": 0, "y": 0, "width": 100, "height": 100})).unwrap());
+    let inner = id(&s.execute("shape.rectangle", &json!({"x": 10, "y": 10, "width": 10, "height": 10, "parent": f})).unwrap());
+    let a = id(&s.execute("shape.rectangle", &json!({"x": 200, "y": 0, "width": 10, "height": 10})).unwrap());
+    let b = id(&s.execute("shape.rectangle", &json!({"x": 220, "y": 0, "width": 10, "height": 10})).unwrap());
+    let g = id(&s.execute("object.group", &json!({"ids": [a, b]})).unwrap());
+    for target in [f, g] {
+        s.execute("vector.offset", &json!({"ids": [target], "offset": 5})).unwrap();
+        assert_children_only_in_containers(&s, &[f, g, inner, a, b]);
+    }
+    let doc = s.doc().unwrap();
+    assert!(doc.node(f).unwrap().kind.is_container());
+    assert_eq!(doc.node(f).unwrap().children, vec![inner]);
+    assert!(doc.node(g).unwrap().kind.is_container());
+    assert_eq!(doc.node(g).unwrap().children.len(), 2);
+}
+
+#[test]
+fn offset_path_still_converts_a_plain_rectangle() {
+    let mut s = Session::new();
+    let r = id(&s.execute("shape.rectangle", &json!({"x": 0, "y": 0, "width": 10, "height": 10})).unwrap());
+    s.execute("vector.offset", &json!({"ids": [r], "offset": 5})).unwrap();
+    let n = s.doc().unwrap().node(r).unwrap().clone();
+    assert!(matches!(n.kind, NodeKind::Vector { .. }));
+    assert!(n.width > 10.0);
+}