Function XCTModify(_:​case:​_:​file:​line:​_:​)

public func XCTModify<Root, Case>(
  _ root: inout Root,
  case casePath: CasePath<Root, Case>,
  _ message: @autoclosure () -> String = "",
  file: StaticString = #file,
  line: UInt = #line,
  _ body: (inout Case) throws -> Void
)