diff --git a/ui/src/ui/components/resizable-divider.test.ts b/ui/src/ui/components/resizable-divider.test.ts
index 71e2237398a..a98af9d3b92 100644
--- a/ui/src/ui/components/resizable-divider.test.ts
+++ b/ui/src/ui/components/resizable-divider.test.ts
@@ -80,6 +80,11 @@ function dispatchPointer(target: EventTarget, type: string, clientX: number) {
   );
 }
 
+function expectLastResizeRatio(resized: ReturnType<typeof vi.fn>, splitRatio: number) {
+  const event = resized.mock.lastCall?.[0] as CustomEvent<{ splitRatio: number }> | undefined;
+  expect(event?.detail.splitRatio).toBe(splitRatio);
+}
+
 describe("resizable-divider", () => {
   beforeEach(() => {
     if (!globalThis.PointerEvent) {
@@ -135,9 +140,7 @@ describe("resizable-divider", () => {
     });
     divider.dispatchEvent(arrowLeft);
     expect(arrowLeft.defaultPrevented).toBe(true);
-    expect(resized).toHaveBeenLastCalledWith(
-      expect.objectContaining({ detail: { splitRatio: 0.58 } }),
-    );
+    expectLastResizeRatio(resized, 0.58);
 
     const arrowRight = new KeyboardEvent("keydown", {
       key: "ArrowRight",
@@ -147,19 +150,13 @@ describe("resizable-divider", () => {
     });
     divider.dispatchEvent(arrowRight);
     expect(arrowRight.defaultPrevented).toBe(true);
-    expect(resized).toHaveBeenLastCalledWith(
-      expect.objectContaining({ detail: { splitRatio: 0.65 } }),
-    );
+    expectLastResizeRatio(resized, 0.65);
 
     divider.dispatchEvent(new KeyboardEvent("keydown", { key: "Home", bubbles: true }));
-    expect(resized).toHaveBeenLastCalledWith(
-      expect.objectContaining({ detail: { splitRatio: 0.4 } }),
-    );
+    expectLastResizeRatio(resized, 0.4);
 
     divider.dispatchEvent(new KeyboardEvent("keydown", { key: "End", bubbles: true }));
-    expect(resized).toHaveBeenLastCalledWith(
-      expect.objectContaining({ detail: { splitRatio: 0.7 } }),
-    );
+    expectLastResizeRatio(resized, 0.7);
   });
 
   it("uses pointer events for mouse, pen, and touch dragging", async () => {
@@ -179,9 +176,7 @@ describe("resizable-divider", () => {
     expect(setPointerCapture).toHaveBeenCalledWith(7);
 
     dispatchPointer(document, "pointermove", 220);
-    expect(resized).toHaveBeenLastCalledWith(
-      expect.objectContaining({ detail: { splitRatio: 0.7 } }),
-    );
+    expectLastResizeRatio(resized, 0.7);
 
     dispatchPointer(document, "pointerup", 220);
     expect(divider.classList.contains("dragging")).toBe(false);