[core] Suppress component source overflow warnings in testing mode (#15320)

esphome/cpp_helpers.py

@@ -71,11 +71,13 @@ def register_component_source(name: str) -> int:
         return pool.sources[name]
     idx = len(pool.sources) + 1
     if idx > _MAX_COMPONENT_SOURCES:
-        _LOGGER.warning(
+        if not CORE.testing_mode:
-            "Too many unique component source names (max %d), '%s' will show as '<unknown>'",
+            _LOGGER.warning(
-            _MAX_COMPONENT_SOURCES,
+                "Too many unique component source names (max %d), "
-            name,
+                "'%s' will show as '<unknown>'",
-        )
+                _MAX_COMPONENT_SOURCES,
+                name,
+            )
         return 0
     pool.sources[name] = idx
     _ensure_source_table_registered()

tests/unit_tests/test_cpp_helpers.py

@@ -140,9 +140,28 @@ def test_register_component_source_overflow_warns(
         sources={f"comp_{i}": i + 1 for i in range(0xFF)},
         table_registered=True,
     )
-    monkeypatch.setattr(ch, "CORE", Mock(data={ch._COMPONENT_SOURCE_DOMAIN: pool}))
+    monkeypatch.setattr(
+        ch, "CORE", Mock(data={ch._COMPONENT_SOURCE_DOMAIN: pool}, testing_mode=False)
+    )
     with caplog.at_level(logging.WARNING):
         idx = register_component_source("overflow_component")
     assert idx == 0
     assert "Too many unique component source names" in caplog.text
     assert "overflow_component" in caplog.text
+
+
+def test_register_component_source_overflow_suppressed_in_testing_mode(
+    monkeypatch: pytest.MonkeyPatch, caplog: pytest.LogCaptureFixture
+) -> None:
+    # Pre-fill pool to max
+    pool = ComponentSourcePool(
+        sources={f"comp_{i}": i + 1 for i in range(0xFF)},
+        table_registered=True,
+    )
+    monkeypatch.setattr(
+        ch, "CORE", Mock(data={ch._COMPONENT_SOURCE_DOMAIN: pool}, testing_mode=True)
+    )
+    with caplog.at_level(logging.WARNING):
+        idx = register_component_source("overflow_component")
+    assert idx == 0
+    assert "Too many unique component source names" not in caplog.text