be consistent with env var names

tests/test_entrypoint.py

@@ -1,6 +1,7 @@
+import io
 from types import SimpleNamespace
 
-from repub.entrypoint import FeedNameFilter
+from repub.entrypoint import FeedNameFilter, entrypoint, logger, parse_args
 
 
 def test_feed_name_filter_accepts_matching_item() -> None:
@@ -15,3 +16,31 @@ def test_feed_name_filter_rejects_non_matching_item() -> None:
     feed_filter = FeedNameFilter({"feed_name": "nasa"})
 
     assert feed_filter.accepts(item) is False
+
+
+def test_parse_args_uses_republisher_host_and_port_env_vars(monkeypatch) -> None:
+    monkeypatch.setenv("REPUBLISHER_HOST", "0.0.0.0")
+    monkeypatch.setenv("REPUBLISHER_PORT", "9090")
+
+    command, args = parse_args(["serve"])
+
+    assert command == "serve"
+    assert args.host == "0.0.0.0"
+    assert args.port == "9090"
+
+
+def test_entrypoint_rejects_invalid_republisher_port(monkeypatch) -> None:
+    monkeypatch.setenv("REPUBLISHER_PORT", "not-a-number")
+    stream = io.StringIO()
+    original_streams = [handler.stream for handler in logger.handlers]
+    for handler in logger.handlers:
+        handler.stream = stream
+
+    try:
+        exit_code = entrypoint(["serve"])
+    finally:
+        for handler, original_stream in zip(logger.handlers, original_streams):
+            handler.stream = original_stream
+
+    assert exit_code == 2
+    assert "Invalid REPUBLISHER_PORT/--port value" in stream.getvalue()