Make synthetic browser checks independent of private files and timing (#45)

tests/browser.spec.ts

@@ -90,11 +90,9 @@ test("actual WASM executes an original cartridge, reads input and round-trips st
     const emulator = new BinjgbEmulator((error) => {
       throw error;
     });
-    const wait = () => new Promise((resolve) => setTimeout(resolve, 180));
     await emulator.load(new Uint8Array(bytes), canvas);
-    emulator.play();
-    await wait();
-    emulator.pause();
+    // Advance emulated frames independently of the CI browser's animation rate.
+    emulator.advanceFrames(12);
     const before = emulator.exportBattery();
     const state = emulator.captureState();
     const pixels = canvas.getContext("2d")!.getImageData(0, 0, 160, 144).data;
@@ -102,9 +100,7 @@ test("actual WASM executes an original cartridge, reads input and round-trips st
     for (let i = 0; i < pixels.length; i += 4)
       colors.add(`${pixels[i]},${pixels[i + 1]},${pixels[i + 2]}`);
     emulator.setButton("a", true);
-    emulator.play();
-    await wait();
-    emulator.pause();
+    emulator.advanceFrames(12);
     const pressed = emulator.exportBattery()[0];
     emulator.restoreState(state);
     const restored = emulator.exportBattery()[0];