test(embedding): тесты retry для embedding провайдеров и backward compat

- test_embedding_retry_integration: OpenAI и VikingDB retry на transient/permanent ошибки
- test_retry_config: VLMConfig и EmbeddingConfig max_retries поля и defaults
- test_backward_compat: exponential_backoff_retry importable, signature unchanged, time-based

Author: snemesh

tests/unit/test_backward_compat.py

@@ -0,0 +1,172 @@
+# Copyright (c) 2026 Beijing Volcano Engine Technology Co., Ltd.
+# SPDX-License-Identifier: Apache-2.0
+
+"""Backward compatibility tests for the retry migration.
+
+Verifies that:
+- exponential_backoff_retry is still importable from the old location (base.py)
+- exponential_backoff_retry signature is unchanged
+- exponential_backoff_retry behaviour still works (time-based)
+- transient_retry is count-based (different semantics)
+"""
+
+from __future__ import annotations
+
+import inspect
+import time
+from unittest.mock import patch
+
+import pytest
+
+
+class _HttpError(Exception):
+    """Fake HTTP error carrying a numeric status code."""
+
+    def __init__(self, status_code: int, message: str = ""):
+        super().__init__(message or f"HTTP {status_code}")
+        self.status_code = status_code
+
+
+class TestExponentialBackoffRetryImportable:
+
+    def test_importable_from_old_location(self):
+        """exponential_backoff_retry should still be importable from base.py."""
+        from openviking.models.embedder.base import exponential_backoff_retry
+
+        assert callable(exponential_backoff_retry)
+
+
+class TestExponentialBackoffRetrySignature:
+
+    def test_signature_unchanged(self):
+        """exponential_backoff_retry should retain its original signature."""
+        from openviking.models.embedder.base import exponential_backoff_retry
+
+        sig = inspect.signature(exponential_backoff_retry)
+        param_names = list(sig.parameters.keys())
+
+        expected_params = [
+            "func",
+            "max_wait",
+            "base_delay",
+            "max_delay",
+            "jitter",
+            "is_retryable",
+            "logger",
+        ]
+
+        assert param_names == expected_params, (
+            f"exponential_backoff_retry signature changed.\n"
+            f"Expected: {expected_params}\n"
+            f"Got:      {param_names}"
+        )
+
+    def test_defaults_unchanged(self):
+        """Default parameter values should be preserved."""
+        from openviking.models.embedder.base import exponential_backoff_retry
+
+        sig = inspect.signature(exponential_backoff_retry)
+        params = sig.parameters
+
+        assert params["max_wait"].default == 10.0
+        assert params["base_delay"].default == 0.5
+        assert params["max_delay"].default == 2.0
+        assert params["jitter"].default is True
+        assert params["is_retryable"].default is None
+        assert params["logger"].default is None
+
+
+class TestExponentialBackoffRetryBehavior:
+
+    def test_success_first_try(self):
+        """Function succeeds on first attempt."""
+        from openviking.models.embedder.base import exponential_backoff_retry
+
+        call_count = 0
+
+        def fn():
+            nonlocal call_count
+            call_count += 1
+            return "ok"
+
+        result = exponential_backoff_retry(fn)
+        assert result == "ok"
+        assert call_count == 1
+
+    def test_retries_on_failure(self):
+        """Function retries on failure until success."""
+        from openviking.models.embedder.base import exponential_backoff_retry
+
+        errors = [Exception("fail"), Exception("fail")]
+        call_count = 0
+
+        def fn():
+            nonlocal call_count
+            call_count += 1
+            if errors:
+                raise errors.pop(0)
+            return "ok"
+
+        with patch("time.sleep"):
+            result = exponential_backoff_retry(fn, max_wait=10.0)
+
+        assert result == "ok"
+        assert call_count == 3
+
+    def test_is_time_based(self):
+        """exponential_backoff_retry should be time-based (uses max_wait, not count)."""
+        from openviking.models.embedder.base import exponential_backoff_retry
+
+        sig = inspect.signature(exponential_backoff_retry)
+        param_names = list(sig.parameters.keys())
+
+        # Time-based: has max_wait, no max_retries
+        assert "max_wait" in param_names
+        assert "max_retries" not in param_names
+
+    def test_respects_is_retryable(self):
+        """exponential_backoff_retry should respect is_retryable callback."""
+        from openviking.models.embedder.base import exponential_backoff_retry
+
+        call_count = 0
+
+        def fn():
+            nonlocal call_count
+            call_count += 1
+            raise ValueError("permanent")
+
+        # is_retryable returns False => no retry
+        with patch("time.sleep"):
+            with pytest.raises(ValueError):
+                exponential_backoff_retry(fn, is_retryable=lambda e: False)
+
+        assert call_count == 1
+
+
+class TestTransientRetryIsCountBased:
+
+    def test_is_count_based(self):
+        """transient_retry should be count-based (uses max_retries, not max_wait)."""
+        from openviking.models.retry import transient_retry
+
+        sig = inspect.signature(transient_retry)
+        param_names = list(sig.parameters.keys())
+
+        # Count-based: has max_retries, no max_wait
+        assert "max_retries" in param_names
+        assert "max_wait" not in param_names
+
+    def test_different_from_backoff_retry(self):
+        """transient_retry and exponential_backoff_retry should have different signatures."""
+        from openviking.models.embedder.base import exponential_backoff_retry
+        from openviking.models.retry import transient_retry
+
+        backoff_params = set(inspect.signature(exponential_backoff_retry).parameters.keys())
+        retry_params = set(inspect.signature(transient_retry).parameters.keys())
+
+        # They share 'func', 'base_delay', 'max_delay', 'jitter', 'is_retryable'
+        # but differ on time vs count control params
+        assert "max_wait" in backoff_params
+        assert "max_wait" not in retry_params
+        assert "max_retries" in retry_params
+        assert "max_retries" not in backoff_params