diff --git a/tests/test_amsc_awos_sources.py b/tests/test_amsc_awos_sources.py
index 52d7fece..440aa60c 100644
--- a/tests/test_amsc_awos_sources.py
+++ b/tests/test_amsc_awos_sources.py
@@ -74,7 +74,8 @@ def test_parse_wind_plate_payload_rejects_unauthorized_or_empty_payloads():
 
 
 def test_fetch_amsc_official_current_uses_domestic_city_whitelist(monkeypatch):
-    monkeypatch.setenv("AMSC_AWOS_BASE_URL", "https://www.amsc.net.cn/gateway/api/saas/rest/amc/AwosController/getWindPlate")
+    import src.data_collection.amsc_awos_sources as _amsc
+    monkeypatch.setattr(_amsc, "AMSC_AWOS_BASE_URL", "https://www.amsc.net.cn/gateway/api/saas/rest/amc/AwosController/getWindPlate")
     assert _amsc_supported_city_codes()["beijing"] == "ZBAA"
     assert "new york" not in _amsc_supported_city_codes()
 
diff --git a/tests/test_nmc_sources.py b/tests/test_nmc_sources.py
index 4caf1eea..3240cc30 100644
--- a/tests/test_nmc_sources.py
+++ b/tests/test_nmc_sources.py
@@ -41,7 +41,8 @@ class _DummyCollector(NmcSourceMixin):
 
 
 def test_fetch_nmc_region_current_parses_rest_payload(monkeypatch):
-    monkeypatch.setenv("NMC_REALTIME_BASE_URL", "https://www.nmc.cn/rest/real")
+    import src.data_collection.nmc_sources as _nmc
+    monkeypatch.setattr(_nmc, "_NMC_REALTIME_BASE", "https://www.nmc.cn/rest/real")
     collector = _DummyCollector(
         {
             "https://www.nmc.cn/rest/real/atcMf": _DummyResponse(
@@ -72,7 +73,8 @@ def test_fetch_nmc_region_current_parses_rest_payload(monkeypatch):
 
 
 def test_fetch_nmc_official_nearby_returns_normalized_row(monkeypatch):
-    monkeypatch.setenv("NMC_REALTIME_BASE_URL", "https://www.nmc.cn/rest/real")
+    import src.data_collection.nmc_sources as _nmc
+    monkeypatch.setattr(_nmc, "_NMC_REALTIME_BASE", "https://www.nmc.cn/rest/real")
     collector = _DummyCollector(
         {
             "https://www.nmc.cn/rest/real/atcMf": _DummyResponse(