test: cover GetNumThreads default

Author: aobolensk

modules/core/util/tests/util.cpp

@@ -2,6 +2,7 @@
 
 #include <gtest/gtest.h>
 
+#include <cstdlib>
 #include <string_view>
 
 #include "omp.h"
@@ -26,6 +27,24 @@ TEST(util_tests, threads_control_check_openmp_disabled_valgrind) {
   ASSERT_EQ(ppc_num_threads, omp_num_threads);
 }
 
+TEST(util_tests, GetNumThreadsEnvUnsetReturnsOne) {
+  const char* old_value = std::getenv("PPC_NUM_THREADS");
+  std::string saved_value;
+  if (old_value != nullptr) {
+    saved_value = old_value;
+  }
+
+  unsetenv("PPC_NUM_THREADS");
+
+  EXPECT_EQ(ppc::util::GetNumThreads(), 1);
+
+  if (old_value != nullptr) {
+    setenv("PPC_NUM_THREADS", saved_value.c_str(), 1);
+  } else {
+    unsetenv("PPC_NUM_THREADS");
+  }
+}
+
 namespace test_ns {
 struct TypeInNamespace {};
 }  // namespace test_ns