test+ci: add regression tests and GitHub Actions workflow

tests/test_config.py

@@ -0,0 +1,43 @@
+from __future__ import annotations
+
+from pathlib import Path
+
+from twitter_cli.config import DEFAULT_CONFIG, load_config
+
+
+def test_load_config_supports_block_list_yaml(tmp_path: Path) -> None:
+    config_file = tmp_path / "config.yaml"
+    config_file.write_text(
+        "\n".join(
+            [
+                "fetch:",
+                "  count: 25",
+                "filter:",
+                "  mode: score",
+                "  lang:",
+                "    - en",
+                "    - zh",
+            ]
+        ),
+        encoding="utf-8",
+    )
+
+    config = load_config(str(config_file))
+    assert config["fetch"]["count"] == 25
+    assert config["filter"]["mode"] == "score"
+    assert config["filter"]["lang"] == ["en", "zh"]
+
+
+def test_load_config_invalid_yaml_falls_back_to_defaults(tmp_path: Path) -> None:
+    config_file = tmp_path / "config.yaml"
+    config_file.write_text("fetch: [", encoding="utf-8")
+
+    config = load_config(str(config_file))
+    assert config["fetch"]["count"] == DEFAULT_CONFIG["fetch"]["count"]
+    assert config["filter"]["mode"] == DEFAULT_CONFIG["filter"]["mode"]
+
+
+def test_load_config_does_not_mutate_defaults(tmp_path: Path) -> None:
+    config = load_config(str(tmp_path / "missing-config.yaml"))
+    config["filter"]["weights"]["likes"] = 999
+    assert DEFAULT_CONFIG["filter"]["weights"]["likes"] == 1.0