tests: Fix test FormatDateTime with invalid formats on MacOS

test/base-utility.cpp

@@ -199,7 +199,15 @@ BOOST_AUTO_TEST_CASE(FormatDateTime) {
 		// treat them as an error which our implementation currently maps to the empty string due to strftime() not
 		// properly reporting errors. If this limitation of our implementation is lifted, other behavior like throwing
 		// an exception would also be valid.
-		BOOST_CHECK_MESSAGE(result.empty() || result == format,
+
+		std::string darwinBug(format);
+		// On Darwin/MacOS, strftime() appears to have a nasty bug that causes the '%' character not to be
+		// populated into the results buffer if invalid format specifiers such as "x %! y" are given.
+		// If such specifiers are provided, the output will contain "x ! y" instead of the given invalid
+		// format specifiers.
+		darwinBug.erase(std::remove(darwinBug.begin(), darwinBug.end(), '%'), darwinBug.end());
+
+		BOOST_CHECK_MESSAGE(result.empty() || result == format || result == darwinBug,
 			"FormatDateTime(" << std::quoted(format) << ", " << ts << ") = " << std::quoted(result) <<
 			" should be one of [\"\", " << std::quoted(format) << "]");
 	}