Before:
  call ale#assert#SetUpLinterTest('cpp', 'clang')
  let b:command_tail = ' -S -x c++ -fsyntax-only -iquote'
  \   . ' ' . ale#Escape(getcwd())
  \   . ' -std=c++14 -Wall -'

After:
  unlet! b:command_tail
  call ale#assert#TearDownLinterTest()

Execute(The executable should be configurable):
  AssertLinter 'clang++', ale#Escape('clang++') . b:command_tail

  let b:ale_cpp_clang_executable = 'foobar'

  AssertLinter 'foobar', ale#Escape('foobar') . b:command_tail