test(telemetry): add code override and validation tests for extended heartbeat interval

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: khanayan123

test/telemetry/test_configuration.cpp

@@ -34,6 +34,7 @@ TELEMETRY_CONFIGURATION_TEST("code override") {
   cfg.report_metrics = false;
   cfg.metrics_interval_seconds = 1;
   cfg.heartbeat_interval_seconds = 2;
+  cfg.extended_heartbeat_interval_seconds = 3600;
   cfg.integration_name = "test";
   cfg.integration_version = "2024.10.28";
 
@@ -45,6 +46,7 @@ TELEMETRY_CONFIGURATION_TEST("code override") {
   CHECK(final_cfg->report_metrics == false);
   CHECK(final_cfg->metrics_interval == 1s);
   CHECK(final_cfg->heartbeat_interval == 2s);
+  CHECK(final_cfg->extended_heartbeat_interval == 3600s);
   CHECK(final_cfg->integration_name == "test");
   CHECK(final_cfg->integration_version == "2024.10.28");
 }
@@ -156,6 +158,22 @@ TELEMETRY_CONFIGURATION_TEST("validation") {
       REQUIRE(!final_cfg);
     }
   }
+
+  SECTION("extended heartbeat interval validation") {
+    SECTION("code override") {
+      telemetry::Configuration cfg;
+      cfg.extended_heartbeat_interval_seconds = -100;
+
+      auto final_cfg = telemetry::finalize_config(cfg);
+      REQUIRE(!final_cfg);
+    }
+
+    SECTION("environment variable override") {
+      ddtest::EnvGuard env("DD_TELEMETRY_EXTENDED_HEARTBEAT_INTERVAL", "-1");
+      auto final_cfg = telemetry::finalize_config();
+      REQUIRE(!final_cfg);
+    }
+  }
 }
 
 TELEMETRY_CONFIGURATION_TEST("installation infos are used when available") {