test(tui): expose native render stats on the harness

Author: TheGreatAxios

src/tui/harness.test.ts

@@ -56,4 +56,38 @@ describe("withTestRenderer", () => {
       expect(ctrlC.ctrl).toBe(true);
     });
   });
+
+  test("surfaces native stats and advances nativeFrameCount across renderOnce", async () => {
+    await withTestRenderer(
+      async (h) => {
+        expect(typeof h.waitForVisualIdle).toBe("function");
+        expect(typeof h.externalOutput.take).toBe("function");
+        expect(h.externalOutput.take()).toEqual([]);
+
+        const before = h.getNativeStats();
+        expect(typeof before.nativeLastFrameTime).toBe("number");
+        expect(typeof before.nativeAverageFrameTime).toBe("number");
+        expect(typeof before.cellsUpdated).toBe("number");
+        expect(typeof before.averageCellsUpdated).toBe("number");
+
+        const box = new BoxRenderable(h.renderer, {
+          id: "stats",
+          width: "100%",
+          height: "100%",
+        });
+        box.add(
+          new TextRenderable(h.renderer, {
+            content: "native-stats",
+          }),
+        );
+        h.root.add(box);
+
+        await h.renderOnce();
+        const after = h.getNativeStats();
+        expect(after.nativeFrameCount).toBeGreaterThan(before.nativeFrameCount);
+        await h.waitForVisualIdle();
+      },
+      { width: 40, height: 10 },
+    );
+  });
 });

src/tui/harness.ts

@@ -119,6 +119,10 @@ export interface Harness {
   readonly flush: TestRendererSetup["flush"];
   readonly waitFor: TestRendererSetup["waitFor"];
   readonly waitForFrame: TestRendererSetup["waitForFrame"];
+  readonly waitForVisualIdle: TestRendererSetup["waitForVisualIdle"];
+  /** Recorded external stdout commits from the test renderer. */
+  readonly externalOutput: TestRendererSetup["externalOutput"];
+  readonly getNativeStats: TestRendererSetup["getNativeStats"];
   readonly captureCharFrame: () => string;
   readonly captureSpans: TestRendererSetup["captureSpans"];
   readonly resize: (width: number, height: number) => void;
@@ -196,6 +200,9 @@ export async function createHarness(
     flush: setup.flush,
     waitFor: setup.waitFor,
     waitForFrame: setup.waitForFrame,
+    waitForVisualIdle: setup.waitForVisualIdle,
+    externalOutput: setup.externalOutput,
+    getNativeStats: setup.getNativeStats,
     captureCharFrame: setup.captureCharFrame,
     captureSpans: setup.captureSpans,
     resize: setup.resize,