R/test-that.R

In hadley/testthat: Unit Testing for R

#' Run a test
#'
#' @description
#' A test encapsulates a series of expectations about a small, self-contained
#' unit of functionality. Each test contains one or more expectations, such as
#' [expect_equal()] or [expect_error()], and lives in a `test/testhat/test*`
#' file, often together with other tests that relate to the same function or set
#' of functions.
#'
#' Each test has its own execution environment, so an object created in a test
#' also dies with the test. Note that this cleanup does not happen automatically
#' for other aspects of global state, such as session options or filesystem
#' changes. Avoid changing global state, when possible, and reverse any changes
#' that you do make.
#'
#' @param desc Test name. Names should be brief, but evocative. It's common to
#'   write the description so that it reads like a natural sentence, e.g.
#'   `test_that("multiplication works", { ... })`.
#' @param code Test code containing expectations. Braces (`{}`) should always
#'   be used in order to get accurate location data for test failures.
#' @return When run interactively, returns `invisible(TRUE)` if all tests
#'   pass, otherwise throws an error.
#' @export
#' @examples
#' test_that("trigonometric functions match identities", {
#'   expect_equal(sin(pi / 4), 1 / sqrt(2))
#'   expect_equal(cos(pi / 4), 1 / sqrt(2))
#'   expect_equal(tan(pi / 4), 1)
#' })
#'
#' \dontrun{
#' test_that("trigonometric functions match identities", {
#'   expect_equal(sin(pi / 4), 1)
#' })
#' }
test_that <- function(desc, code) {
  check_string(desc)

  code <- substitute(code)
  if (edition_get() >= 3) {
    if (!is_call(code, "{")) {
      warn(
        "The `code` argument to `test_that()` must be a braced expression to get accurate file-line information for failures.",
        class = "testthat_braces_warning"
      )
    }
  }

  local_test_context()
  test_code(
    desc,
    code,
    env = parent.frame(),
    default_reporter = local_interactive_reporter()
  )
}

# Access error fields with `[[` rather than `$` because the
# `$.Throwable` from the rJava package throws with unknown fields
test_code <- function(test, code, env, default_reporter, skip_on_empty = TRUE) {

  frame <- caller_env()
  reporter <- get_reporter() %||% default_reporter

  if (!is.null(test)) {
    reporter$start_test(context = reporter$.context, test = test)
    on.exit(reporter$end_test(context = reporter$.context, test = test))
  }

  ok <- TRUE

  # @param debug_end How many frames should be skipped to find the
  #   last relevant frame call. Only useful for the DebugReporter.
  register_expectation <- function(e, debug_end) {
    srcref <- e[["srcref"]] %||% find_expectation_srcref(frame)
    e <- as.expectation(e, srcref = srcref)

    # Data for the DebugReporter
    if (debug_end >= 0) {
      start <- eval_bare(quote(base::sys.nframe()), test_env) + 1L
      e$start_frame <- start
      e$end_frame <- sys.nframe() - debug_end - 1L
    }

    e$test <- test %||% "(code run outside of `test_that()`)"

    ok <<- ok && expectation_ok(e)
    reporter$add_result(context = reporter$.context, test = test, result = e)
  }

  # Any error will be assigned to this variable first
  # In case of stack overflow, no further processing (not even a call to
  # signalCondition() ) might be possible
  test_error <- NULL

  expressions_opt <- getOption("expressions")
  expressions_opt_new <- min(expressions_opt + 500L, 500000L)

  # If no handlers are called we skip: BDD (`describe()`) tests are often
  # nested and the top level might not contain any expectations, so we need
  # some way to disable
  handled <- !skip_on_empty

  handle_error <- function(e) {
    handled <<- TRUE
    # First thing: Collect test error
    test_error <<- e

    # Increase option(expressions) to handle errors here if possible, even in
    # case of a stack overflow.  This is important for the DebugReporter.
    # Call options() manually, avoid withr overhead.
    options(expressions = expressions_opt_new)
    on.exit(options(expressions = expressions_opt), add = TRUE)

    # Add structured backtrace to the expectation
    if (can_entrace(e)) {
      e <- cnd_entrace(e)
    }

    test_error <<- e

    # Error will be handled by handle_fatal() if this fails; need to do it here
    # to be able to debug with the DebugReporter
    register_expectation(e, 2)

    e[["handled"]] <- TRUE
    test_error <<- e
  }
  handle_fatal <- function(e) {
    handled <<- TRUE
    # Error caught in handle_error() has precedence
    if (!is.null(test_error)) {
      e <- test_error
      if (isTRUE(e[["handled"]])) {
        return()
      }
    }

    register_expectation(e, 0)
  }
  handle_expectation <- function(e) {
    handled <<- TRUE
    register_expectation(e, 6)
    invokeRestart("continue_test")
  }
  handle_warning <- function(e) {
    # When options(warn) < 0, warnings are expected to be ignored.
    if (getOption("warn") < 0) {
      return()
    }

    # When options(warn) >= 2, warnings are converted to errors.
    # So, do not handle it here so that it will be handled by handle_error.
    if (getOption("warn") >= 2) {
      return()
    }

    if (!inherits(e, "testthat_warn")) {
      e <- cnd_entrace(e)
    }

    register_expectation(e, 5)

    maybe_restart("muffleWarning")
  }
  handle_message <- function(e) {
    if (edition_get() < 3) {
     maybe_restart("muffleMessage")
    }
  }
  handle_skip <- function(e) {
    handled <<- TRUE

    debug_end <- if (inherits(e, "skip_empty")) -1 else 2
    register_expectation(e, debug_end)
    signalCondition(e)
  }

  test_env <- new.env(parent = env)
  old <- options(rlang_trace_top_env = test_env)[[1]]
  on.exit(options(rlang_trace_top_env = old), add = TRUE)

  withr::local_options(testthat_topenv = test_env)

  before <- inspect_state()
  tryCatch(
    withCallingHandlers(
      {
        eval(code, test_env)
        if (!handled && !is.null(test)) {
          skip_empty()
        }
      },
      expectation = handle_expectation,
      skip =        handle_skip,
      warning =     handle_warning,
      message =     handle_message,
      error =       handle_error
    ),
    # some errors may need handling here, e.g., stack overflow
    error = handle_fatal,
    # skip silently terminate code
    skip  = function(e) {}
  )
  after <- inspect_state()

  if (!is.null(test)) {
    cnd <- testthat_state_condition(before, after, call = sys.call(-1))
    if (!is.null(cnd)) {
      register_expectation(cnd, 0)
    }
  }

  invisible(ok)
}