Phase 1-2 (PLAN_MASTERBUS_FX_RACK_VST): tests cho render_fx_chain + API fx-render; plan HOÀN THÀNH Phase 0-4

- test_native_render: render_fx_chain builtin gain e2e (bridge --render-fx)
- test_plugin_api: POST /api/v1/plugins/fx-render builtin gain
- PLAN_MASTERBUS_FX_RACK_VST.md: cap nhat trang thai cac phase (0-4 da implement tu cac commit truoc + phan nay)

tests/test_native_render.py

@@ -66,3 +66,30 @@ def test_plugins_bridge_branch_dispatch(monkeypatch):
     with pytest.raises(HTTPException) as ei:
         pl._render_midi_notes_pedalboard("__no_such__", [], bpm=120.0, sample_rate=44100)
     assert ei.value.status_code == 404
+def test_render_fx_chain_builtin_gain_e2e():
+    """render_fx_chain (PLAN_MASTERBUS_FX_RACK_VST Phase 1): builtin gain
+    +6dB qua bridge --render-fx, không cần VST. Output tồn tại, đúng sr,
+    RMS gấp đôi input."""
+    import math
+    import numpy as np
+    import soundfile as sf
+    exe = native_render.find_bridge_exe()
+    if not exe:
+        pytest.skip("bridge exe missing")
+    sr = 44100
+    t = np.linspace(0, 1.0, sr, endpoint=False)
+    data = (0.1 * np.sin(2 * np.pi * 440 * t)).astype(np.float32)
+    with tempfile.TemporaryDirectory() as td:
+        inp = os.path.join(td, "in.wav")
+        sf.write(inp, data, sr, subtype="FLOAT")
+        out = native_render.render_fx_chain(
+            input_wav=inp,
+            fx_chain=[{"type": "builtin", "id": "gain", "params": {"db": 6.0}}],
+            sample_rate=sr,
+        )
+        assert os.path.isfile(out)
+        d, _ = sf.read(out, dtype="float32", always_2d=True)
+        rms = float(np.sqrt(np.mean(d ** 2)))
+        assert rms > 0.09  # ~2x 0.05
+        info = sf.info(out)
+        assert info.samplerate == sr

tests/test_plugin_api.py

@@ -30,6 +30,47 @@ def get_admin_token():
 
 
 class TestPluginAPI:
+    def test_fx_render_builtin_gain(self):
+        """POST /api/v1/plugins/fx-render với builtin gain (bridge --render-fx),
+        không cần VST — output WAV mới trong PROCESSED_DIR."""
+        import numpy as np
+        import soundfile as sf
+        from app.core import native_render
+        from app.config import settings
+        exe = native_render.find_bridge_exe()
+        if not exe:
+            pytest.skip("bridge exe missing")
+        token = get_admin_token()
+        if not token:
+            pytest.skip("no admin token")
+        h = {"Authorization": f"Bearer {token}"}
+        sr = 44100
+        t = np.linspace(0, 0.5, int(sr * 0.5), endpoint=False)
+        data = (0.05 * np.sin(2 * np.pi * 440 * t)).astype(np.float32)
+        os.makedirs(settings.PROCESSED_DIR, exist_ok=True)
+        inp = os.path.join(settings.PROCESSED_DIR, "fx_api_in_test.wav")
+        sf.write(inp, data, sr, subtype="FLOAT")
+        try:
+            resp = client.post("/api/v1/plugins/fx-render", headers=h, json={
+                "input_file_id": "fx_api_in_test.wav",
+                "fx_chain": [{"type": "builtin", "id": "gain", "params": {"db": 6.0}}],
+                "sample_rate": sr,
+            })
+            assert resp.status_code == 200, resp.text[-500:]
+            body = resp.json()
+            assert body["success"] is True
+            assert os.path.isfile(body["path"])
+            d, _ = sf.read(body["path"], dtype="float32", always_2d=True)
+            assert float(np.max(np.abs(d))) > 0.07  # ~2x 0.05
+        finally:
+            client.cookies.clear()  # không làm hỏng test requires_auth kế tiếp
+            for f in (inp, os.path.join(settings.PROCESSED_DIR, "fx_api_out_test.wav")):
+                if os.path.exists(f):
+                    try:
+                        os.remove(f)
+                    except Exception:
+                        pass
+
     def test_list_plugins_requires_auth(self):
         resp = client.get("/api/v1/plugins/available")
         assert resp.status_code in (401, 403)