test(v1.4.0-p1): add failing tests for timeout and YAML config

RED phase: 4 new tests in test_client.py for graceful timeout on
pagination, 12 new tests in test_config.py for YAML config module
(import fails, module not created yet).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/test_config.py

@@ -0,0 +1,133 @@
+"""Tests for YAML configuration module."""
+
+from __future__ import annotations
+
+import os
+from unittest.mock import patch
+
+import pytest
+
+from gitea_dashboard.config import load_config, merge_config, resolve_env_vars
+
+
+class TestResolveEnvVars:
+    """Test resolve_env_vars function."""
+
+    def test_resolve_env_vars_simple(self):
+        """${VAR} is replaced by the environment variable value."""
+        with patch.dict(os.environ, {"GITEA_TOKEN": "abc123"}):
+            result = resolve_env_vars("${GITEA_TOKEN}")
+
+        assert result == "abc123"
+
+    def test_resolve_env_vars_undefined(self):
+        """${UNDEFINED} is left as-is when the variable is not set."""
+        with patch.dict(os.environ, {}, clear=True):
+            result = resolve_env_vars("${UNDEFINED_VAR}")
+
+        assert result == "${UNDEFINED_VAR}"
+
+    def test_resolve_env_vars_in_list(self):
+        """resolve_env_vars works on individual string elements."""
+        with patch.dict(os.environ, {"MY_VAR": "resolved"}):
+            result = resolve_env_vars("prefix-${MY_VAR}-suffix")
+
+        assert result == "prefix-resolved-suffix"
+
+
+class TestLoadConfig:
+    """Test load_config function."""
+
+    def test_load_config_valid_yaml(self, tmp_path):
+        """Valid YAML file is loaded as a dict with all keys."""
+        config_file = tmp_path / "config.yml"
+        config_file.write_text(
+            "url: http://localhost:3000\ntoken: ${GITEA_TOKEN}\nsort: activity\n"
+        )
+
+        with patch.dict(os.environ, {"GITEA_TOKEN": "secret123"}):
+            result = load_config(str(config_file))
+
+        assert result["url"] == "http://localhost:3000"
+        assert result["token"] == "secret123"
+        assert result["sort"] == "activity"
+
+    def test_load_config_partial_yaml(self, tmp_path):
+        """YAML with only some keys returns a partial dict."""
+        config_file = tmp_path / "config.yml"
+        config_file.write_text("url: http://localhost:3000\nsort: name\n")
+
+        result = load_config(str(config_file))
+
+        assert result["url"] == "http://localhost:3000"
+        assert result["sort"] == "name"
+        assert "token" not in result
+
+    def test_load_config_empty_file(self, tmp_path):
+        """Empty YAML file returns an empty dict."""
+        config_file = tmp_path / "config.yml"
+        config_file.write_text("")
+
+        result = load_config(str(config_file))
+
+        assert result == {}
+
+    def test_load_config_invalid_yaml(self, tmp_path):
+        """Syntactically invalid YAML raises a clear error."""
+        config_file = tmp_path / "config.yml"
+        config_file.write_text("invalid: yaml: content: [unclosed")
+
+        with pytest.raises(ValueError, match="[Ii]nvalid"):
+            load_config(str(config_file))
+
+    def test_load_config_custom_path(self, tmp_path):
+        """--config /path/to/custom.yml loads the specified file."""
+        config_file = tmp_path / "custom.yml"
+        config_file.write_text("sort: issues\n")
+
+        result = load_config(str(config_file))
+
+        assert result["sort"] == "issues"
+
+    def test_load_config_missing_custom_path(self):
+        """--config with a nonexistent path raises FileNotFoundError."""
+        with pytest.raises(FileNotFoundError):
+            load_config("/nonexistent/path/config.yml")
+
+    def test_load_config_default_paths(self, tmp_path, monkeypatch):
+        """Config file in current directory is auto-discovered."""
+        config_file = tmp_path / ".gitea-dashboard.yml"
+        config_file.write_text("sort: activity\n")
+        monkeypatch.chdir(tmp_path)
+
+        result = load_config()
+
+        assert result["sort"] == "activity"
+
+
+class TestMergeConfig:
+    """Test merge_config function."""
+
+    def test_merge_config_priority(self):
+        """CLI > env > config > defaults — CLI wins."""
+        cli = {"sort": "name", "url": None}
+        env = {"sort": "issues", "url": "http://env:3000"}
+        config = {"sort": "activity", "url": "http://config:3000", "exclude": ["old"]}
+        defaults = {"sort": "name", "url": "http://default:3000", "exclude": None}
+
+        result = merge_config(cli, env, config, defaults)
+
+        assert result["sort"] == "name"  # CLI wins
+        assert result["url"] == "http://env:3000"  # CLI is None, env wins
+        assert result["exclude"] == ["old"]  # env has no exclude, config wins
+
+    def test_merge_config_none_does_not_override(self):
+        """None in a higher-priority source does not mask a lower-priority value."""
+        cli = {"token": None}
+        env = {"token": None}
+        config = {"token": "from-config"}
+        defaults = {"token": "default-token"}
+
+        result = merge_config(cli, env, config, defaults)
+
+        assert result["token"] == "from-config"