[tests] Reset shared App state before every host test (#20510)

tests/components/main.cpp

@@ -1,6 +1,7 @@
 #include <gtest/gtest.h>
 
 #include "esphome/components/logger/logger.h"
+#include "esphome/core/application.h"
 
 /*
 This special main.cpp replaces the default one.
@@ -19,6 +20,11 @@ void original_setup() {
   // =========== AUTO GENERATED CODE END ============
 }
 
+// The loop clock and current component one test moves must not leak into the next, like CORE.reset() in Python
+class ResetAppListener : public ::testing::EmptyTestEventListener {
+  void OnTestStart(const ::testing::TestInfo &) override { esphome::LoopBlockingGuard reset{nullptr, nullptr, 0}; }
+};
+
 void setup() {
   // Log functions call global_logger->log_vprintf_() without a null check,
   // so we must set up a Logger before any test that triggers logging.
@@ -27,6 +33,7 @@ void setup() {
   test_logger.pre_setup();
 
   ::testing::InitGoogleTest();
+  ::testing::UnitTest::GetInstance()->listeners().Append(new ResetAppListener);
   int exit_code = RUN_ALL_TESTS();
   // A test folder that never reached the build would otherwise pass as an empty run
   if (::testing::UnitTest::GetInstance()->total_test_count() == 0) {