From 18febfeaf2e49691cc1668805bc1a1c59396ac51 Mon Sep 17 00:00:00 2001
From: Ryan Di <ryan.weihao.di@gmail.com>
Date: Tue, 28 Apr 2026 16:02:13 +1000
Subject: [PATCH] test(linear): cover line snapping interactions

---
 .../tests/linearElementEditor.test.tsx        | 92 ++++++++++++++++++-
 1 file changed, 90 insertions(+), 2 deletions(-)

diff --git a/packages/element/tests/linearElementEditor.test.tsx b/packages/element/tests/linearElementEditor.test.tsx
index 45be3b76e6..95feeb933c 100644
--- a/packages/element/tests/linearElementEditor.test.tsx
+++ b/packages/element/tests/linearElementEditor.test.tsx
@@ -155,6 +155,24 @@ describe("Test Linear Elements", () => {
     });
   };
 
+  const dragMove = (startPoint: GlobalPoint, endPoint: GlobalPoint) => {
+    fireEvent.pointerDown(interactiveCanvas, {
+      clientX: startPoint[0],
+      clientY: startPoint[1],
+    });
+    fireEvent.pointerMove(interactiveCanvas, {
+      clientX: endPoint[0],
+      clientY: endPoint[1],
+    });
+  };
+
+  const dragEnd = (endPoint: GlobalPoint) => {
+    fireEvent.pointerUp(interactiveCanvas, {
+      clientX: endPoint[0],
+      clientY: endPoint[1],
+    });
+  };
+
   const deletePoint = (point: GlobalPoint) => {
     fireEvent.pointerDown(interactiveCanvas, {
       clientX: point[0],
@@ -258,6 +276,43 @@ describe("Test Linear Elements", () => {
     expect(h.state.selectedLinearElement?.elementId).toEqual(h.elements[0].id);
   });
 
+  it("shows snap lines and snaps the endpoint when creating a line", () => {
+    const rect = API.createElement({
+      type: "rectangle",
+      x: 100,
+      y: 100,
+      width: 40,
+      height: 40,
+    });
+    API.setElements([rect]);
+    API.setAppState({ objectsSnapModeEnabled: true });
+
+    UI.clickTool("line");
+
+    const startPoint = pointFrom<GlobalPoint>(20, 20);
+    const pointerNearCorner = pointFrom<GlobalPoint>(95, 95);
+
+    dragMove(startPoint, pointerNearCorner);
+
+    expect(h.state.snapLines.length).toBeGreaterThan(0);
+
+    dragEnd(pointerNearCorner);
+
+    const line = h.elements.find(
+      (element): element is ExcalidrawLinearElement => element.type === "line",
+    );
+
+    expect(line).toBeDefined();
+
+    const endpoint = LinearElementEditor.getPointGlobalCoordinates(
+      line!,
+      line!.points[line!.points.length - 1],
+      h.app.scene.getNonDeletedElementsMap(),
+    );
+
+    expect(endpoint).toEqual(pointFrom<GlobalPoint>(100, 100));
+  });
+
   it("should enter line editor via enter (line)", () => {
     createTwoPointerLinearElement("line");
     expect(h.state.selectedLinearElement?.isEditing).toBe(false);
@@ -401,6 +456,39 @@ describe("Test Linear Elements", () => {
       `);
     });
 
+    it("shows snap lines when dragging a point to another line point axis", () => {
+      const line = API.createElement({
+        type: "line",
+        x: 20,
+        y: 20,
+        width: 100,
+        height: 50,
+        roughness: 0,
+        points: [
+          pointFrom<LocalPoint>(0, 0),
+          pointFrom<LocalPoint>(50, 50),
+          pointFrom<LocalPoint>(100, 0),
+        ],
+      });
+
+      API.setElements([line]);
+      API.setAppState({ objectsSnapModeEnabled: true });
+      enterLineEditingMode(line);
+
+      const middlePoint = pointFrom<GlobalPoint>(70, 70);
+      const pointerNearEndPointX = pointFrom<GlobalPoint>(117, 65);
+
+      dragMove(middlePoint, pointerNearEndPointX);
+
+      expect(h.state.snapLines.length).toBeGreaterThan(0);
+
+      dragEnd(pointerNearEndPointX);
+
+      expect(API.getElement(line).points[1]).toEqual(
+        pointFrom<LocalPoint>(100, 45),
+      );
+    });
+
     it("should update the midpoints when element roundness changed", async () => {
       createThreePointerLinearElement("line");
 
@@ -548,7 +636,7 @@ describe("Test Linear Elements", () => {
         );
 
         expect(renderInteractiveScene.mock.calls.length).toMatchInlineSnapshot(
-          `16`,
+          `15`,
         );
         expect(renderStaticScene.mock.calls.length).toMatchInlineSnapshot(`9`);
 
@@ -746,7 +834,7 @@ describe("Test Linear Elements", () => {
           ),
         );
         expect(renderInteractiveScene.mock.calls.length).toMatchInlineSnapshot(
-          `16`,
+          `15`,
         );
         expect(renderStaticScene.mock.calls.length).toMatchInlineSnapshot(`9`);
         expect(line.points.length).toEqual(5);