fix: stop masking runtime failures

tests/utils/test_gitstore.py

@@ -7,7 +7,7 @@ from unittest.mock import patch
 
 import pytest
 
-from nanobot.utils.gitstore import GitStore
+from nanobot.utils.gitstore import GitStore, GitStoreError
 
 
 @pytest.fixture
@@ -63,11 +63,13 @@ class TestLineAges:
         assert len(ages) == 2
         assert all(a.age_days == 30 for a in ages)
 
-    def test_annotate_failure_returns_empty(self, tmp_path):
-        """If annotate fails, line_ages should return [] gracefully."""
-        git = GitStore(tmp_path, tracked_files=["MEMORY.md"])
-        # Don't init — annotate will fail
-        assert git.line_ages("MEMORY.md") == []
+    def test_annotate_failure_is_explicit(self, git, tmp_path):
+        (tmp_path / "MEMORY.md").write_text("important\n", encoding="utf-8")
+        git.auto_commit("initial")
+
+        with patch("dulwich.porcelain.annotate", side_effect=OSError("broken repo")):
+            with pytest.raises(GitStoreError, match="annotation failed"):
+                git.line_ages("MEMORY.md")
 
     def test_partial_edit_only_updates_changed_lines(self, git, tmp_path):
         """Only modified lines should reflect the new commit's timestamp."""

tests/utils/test_helpers.py

@@ -1,9 +1,16 @@
 from pathlib import Path
+from zoneinfo import ZoneInfoNotFoundError
 
+import pytest
 import tiktoken
 
 from nanobot.utils import helpers
-from nanobot.utils.helpers import _write_text_atomic, split_message, truncate_text_to_tokens
+from nanobot.utils.helpers import (
+    _write_text_atomic,
+    current_time_str,
+    split_message,
+    truncate_text_to_tokens,
+)
 
 
 def test_split_message_no_code_blocks_unchanged():
@@ -43,6 +50,11 @@ def test_truncate_text_to_tokens_non_positive_budget_returns_text():
     assert truncate_text_to_tokens(text, 0) == text
 
 
+def test_current_time_str_rejects_unknown_timezone():
+    with pytest.raises(ZoneInfoNotFoundError):
+        current_time_str("Not/AZone")
+
+
 def test_write_text_atomic_fsyncs_file_and_parent_directory(
     tmp_path: Path, monkeypatch
 ) -> None:

tests/utils/test_token_estimation.py

@@ -1,7 +1,12 @@
 import json
 
 from nanobot.utils import helpers
-from nanobot.utils.helpers import estimate_prompt_tokens, estimate_prompt_tokens_chain
+from nanobot.utils.helpers import (
+    estimate_message_tokens,
+    estimate_prompt_tokens,
+    estimate_prompt_tokens_chain,
+    truncate_text_to_tokens,
+)
 
 
 class _NoCounterProvider:
@@ -35,6 +40,57 @@ def test_estimate_prompt_tokens_chain_falls_back_when_provider_counter_fails() -
     assert source == "tiktoken"
 
 
+def test_estimate_prompt_tokens_uses_conservative_fallback_when_tiktoken_fails(
+    monkeypatch,
+) -> None:
+    monkeypatch.setattr(
+        helpers,
+        "_get_token_encoding",
+        lambda: (_ for _ in ()).throw(RuntimeError("encoding unavailable")),
+    )
+
+    content = "你" * 1_000
+    messages = [{"role": "user", "content": content}]
+    tokens = estimate_prompt_tokens(messages)
+    chain_tokens, source = estimate_prompt_tokens_chain(
+        _NoCounterProvider(),
+        "test-model",
+        messages,
+    )
+
+    actual_tokens = len(helpers.tiktoken.get_encoding("cl100k_base").encode(content)) + 4
+    assert tokens == len(content.encode("utf-8")) + 4
+    assert tokens >= actual_tokens
+    assert chain_tokens == tokens
+    assert source == "heuristic"
+
+
+def test_estimate_message_tokens_uses_utf8_byte_fallback(monkeypatch) -> None:
+    monkeypatch.setattr(
+        helpers,
+        "_get_token_encoding",
+        lambda: (_ for _ in ()).throw(RuntimeError("encoding unavailable")),
+    )
+    content = "🙂你" * 100
+
+    assert estimate_message_tokens({"role": "user", "content": content}) == (
+        len(content.encode("utf-8")) + 4
+    )
+
+
+def test_truncate_text_to_tokens_uses_utf8_byte_budget_fallback(monkeypatch) -> None:
+    monkeypatch.setattr(
+        helpers,
+        "_get_token_encoding",
+        lambda: (_ for _ in ()).throw(RuntimeError("encoding unavailable")),
+    )
+
+    result = truncate_text_to_tokens("🙂你" * 100, 40)
+
+    assert result.endswith("\n... (truncated)")
+    assert len(result.encode("utf-8")) <= 40
+
+
 def test_estimate_prompt_tokens_caches_tools_encoding(monkeypatch) -> None:
     helpers._get_token_encoding.cache_clear()
     helpers._TOOLS_TOKEN_CACHE.clear()