Add a test for custom debug break macros

See #1846

projects/ExtraTests/X12-CustomDebugBreakMacro.cpp

@@ -0,0 +1,17 @@
+// X12-CustomDebugBreakMacro.cpp
+// Test that user-defined `CATCH_BREAK_INTO_DEBUGGER` is respected and used.
+
+#include <iostream>
+
+void custom_debug_break() {
+    std::cerr << "Pretty please, break into debugger\n";
+}
+
+#define CATCH_BREAK_INTO_DEBUGGER() custom_debug_break()
+
+#define CATCH_CONFIG_MAIN
+#include <catch2/catch.hpp>
+
+TEST_CASE("Failing test that breaks into debugger", "[macros]") {
+    REQUIRE(1 == 2);
+}