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test/grabSnapshot.test.js

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+'use strict';
+
+const { CameraSwitch } = require('../src/cameraSwitch');
+
+// Testet die Entscheidungslogik von grabSnapshot() ohne Hardware:
+// _captureAt (FFmpeg) und _spawnLive sind gemockt.
+function makeSwitch(opts = {}) {
+  const sw = new CameraSwitch({ id: 'camT', device: '/dev/null', liveSize: '640x480', ...opts });
+  sw._captureAt = jest.fn(() => Promise.resolve(Buffer.from([0xFF, 0xD8, 9])));
+  sw._spawnLive = jest.fn(() => { sw.proc = {}; sw.state = 'live'; });
+  return sw;
+}
+
+describe('CameraSwitch.grabSnapshot', () => {
+  test('Live läuft (latest gesetzt) → liefert latest, kein Capture', async () => {
+    const sw = makeSwitch({ stream: true });
+    sw.latest = Buffer.from([1, 2, 3]);
+    const f = await sw.grabSnapshot();
+    expect(f).toBe(sw.latest);
+    expect(sw._captureAt).not.toHaveBeenCalled();
+  });
+
+  test('stream:false ohne latest → one-shot _captureAt an liveSize', async () => {
+    const sw = makeSwitch({ stream: false });
+    sw.latest = null;
+    const f = await sw.grabSnapshot();
+    expect(Buffer.isBuffer(f)).toBe(true);
+    expect(sw._captureAt).toHaveBeenCalledTimes(1);
+    expect(sw._captureAt.mock.calls[0][0]).toBe('640x480'); // size = liveSize
+    expect(sw._spawnLive).not.toHaveBeenCalled();           // kein Dauer-Stream
+  });
+
+  test('Lock wird nach dem one-shot wieder freigegeben', async () => {
+    const sw = makeSwitch({ stream: false });
+    sw.latest = null;
+    await sw.grabSnapshot();
+    expect(sw.lock).toBe(false);
+    expect(sw.state).toBe('stopped');
+  });
+
+  test('belegtes Gerät (lock) → Fehler, kein zweiter Capture', async () => {
+    const sw = makeSwitch({ stream: false });
+    sw.latest = null;
+    sw.lock = true;
+    await expect(sw.grabSnapshot()).rejects.toThrow(/belegt/i);
+    expect(sw._captureAt).not.toHaveBeenCalled();
+  });
+});