Expectation refactoring

[hadley]

Use lazyeval to simplify NSE handling.

label <- function(x) {
  paste(deparse(lazyeval::lazy(expected)$expr), collapse = "")
}

expect_identical <- function(actual, expected) {
  if (identical(actual, expected)) {
    success()
  }

  same <- compare(expected, actual)
  if (same$equal) {
    failure(label(actual), "is equal but not identical to ", label(expected))
  } else {
    diff <- paste0(same, collapse = "\n")
    failure(
      label(actual),  "is not identical to ", label(expected), 
      ". Differences: \n", same$message
    )
  }
}