Changes imported from Abseil "staging" branch:

- 8bcd472c6f1a7c8a3a7aac07d7e5e3f90685fe5e Create an exception-safety testing framework for Abseil by Jon Cohen <cohenjon@google.com>
  - 17cc4bb19ba86e2bc45e9381bd07450c06134903 Fix typo. by Abseil Team <absl-team@google.com>

GitOrigin-RevId: 8bcd472c6f1a7c8a3a7aac07d7e5e3f90685fe5e
Change-Id: Ia1f4f12d25c375e0af34fea052a4a82dc964eeff

absl/base/internal/exception_safety_testing.cc

@@ -0,0 +1,21 @@
+#include "absl/base/internal/exception_safety_testing.h"
+
+#include "gtest/gtest.h"
+#include "absl/meta/type_traits.h"
+
+namespace absl {
+namespace exceptions_internal {
+
+int countdown = -1;
+
+void MaybeThrow(absl::string_view msg) {
+  if (countdown-- == 0) throw TestException(msg);
+}
+
+testing::AssertionResult FailureMessage(const TestException& e,
+                                        int countdown) noexcept {
+  return testing::AssertionFailure()
+         << "Exception number " << countdown + 1 << " thrown from " << e.what();
+}
+}  // namespace exceptions_internal
+}  // namespace absl