llvm-project/clang/test/Tooling/clang-check-extra-arg.cpp

// RUN: clang-check "%s" -extra-arg=-Wunimplemented-warning -extra-arg-before=-Wunimplemented-warning-before -- -c 2>&1 | FileCheck %s

// CHECK: unknown warning option '-Wunimplemented-warning-before'
// CHECK: unknown warning option '-Wunimplemented-warning'
void a(){}