tests/testthat/test-start-listening.R

In mdneuzerling/lambdr: Create a Runtime for Serving Containerised R Functions on 'AWS Lambda'

test_that("status code check works", {
  # Make webmockr intercept HTTP requests
  webmockr::enable(quiet = TRUE)
  withr::defer(webmockr::disable(quiet = TRUE))

  request_id <- "abc123"

  good_invocation_endpoint <- paste0(
    "http://", "good_invocation", "/2018-06-01/runtime/invocation/next"
  )
  bad_invocation_endpoint <- paste0(
    "http://", "bad_invocation", "/2018-06-01/runtime/invocation/next"
  )

  webmockr::stub_request("get", good_invocation_endpoint) %>%
    webmockr::to_return(
      body = list(), # input is irrelevant here --- it's never used
      headers = list("lambda-runtime-aws-request-id" = request_id),
      status = 200
    )

  webmockr::stub_request("get", bad_invocation_endpoint) %>%
    webmockr::to_return(
      body = list(), # input is irrelevant here --- it's never used
      headers = list("lambda-runtime-aws-request-id" = request_id),
      status = 500
    )

  good_invocation_response <- httr::GET(good_invocation_endpoint)
  expect_true(
    assert_status_code_is_good(httr::status_code(good_invocation_response))
  )

  bad_invocation_response <- httr::GET(bad_invocation_endpoint)
  expect_error(
    assert_status_code_is_good(httr::status_code(bad_invocation_response)),
    "Didn't get status code 200. Status code: 500"
  )
})

test_that("event headers extracted, prettified and distilled", {

  # Make webmockr intercept HTTP requests
  webmockr::enable(quiet = TRUE)
  withr::defer(webmockr::disable(quiet = TRUE))

  lambda_runtime_api <- "red_panda"
  request_id <- "abc123"
  request_arn <- "arn:aws:lambda:us-west-2:123456789012:function:my-function"

  invocation_endpoint <- get_next_invocation_endpoint(lambda_runtime_api)

  # Mock the invocation to return a Lambda input with mock request ID and input
  webmockr::stub_request("get", invocation_endpoint) %>%
    webmockr::to_return(
      body = list(), # input is irrelevant here --- it's never used
      headers = list(
        "lambda-runtime-aws-request-id" = request_id,
        "LAMBDA-RUNTIME-INVOKED-FUNCTION-ARN" = request_arn
      ),
      status = 200
    )

  invocation <- httr::GET(invocation_endpoint)
  headers <- extract_event_headers(invocation)

  expect_equal(
    headers,
    structure(
      list(
        "lambda-runtime-aws-request-id" = request_id,
        # note the conversion to lower-case:
        "lambda-runtime-invoked-function-arn" = request_arn
      ),
      class = c("insensitive", "list")
    )
  )

  expect_equal(
    prettify_list(headers),
    paste0(
      "lambda-runtime-aws-request-id", "=", request_id, ", ",
      "lambda-runtime-invoked-function-arn", "=", request_arn
    )
  )

  expect_equal(
    headers[["lambda-runtime-aws-request-id"]],
    request_id
  )
})

test_that("error occurs when request ID not in headers", {

  # Make webmockr intercept HTTP requests
  webmockr::enable(quiet = TRUE)
  withr::defer(webmockr::disable(quiet = TRUE))

  lambda_runtime_api <- "red_panda"
  request_id <- "abc123"
  request_arn <- "arn:aws:lambda:us-west-2:123456789012:function:my-function"

  invocation_endpoint <- get_next_invocation_endpoint(lambda_runtime_api)

  # Mock the invocation to return a Lambda input with mock request ID and input
  webmockr::stub_request("get", invocation_endpoint) %>%
    webmockr::to_return(
      body = list(), # input is irrelevant here --- it's never used
      headers = list(
        "LAMBDA-RUNTIME-INVOKED-FUNCTION-ARN" = request_arn
      ),
      status = 200
    )

  # Errors are simply logged and shouldn't stop the runtime.
  # They aren't reported to any endpoints (there's no request_id so there's no
  # endpoint) so we expect no errors from webmockr here either.
  expect_error(
    start_listening(
      config = basic_lambda_config(handler = "sqrt"),
      timeout_seconds = 0.5
    ),
    NA
  )

  requests <- webmockr::request_registry()
  n_responses <- requests$times_executed(
    webmockr::RequestPattern$new("get", invocation_endpoint)
  )

  # Should be more than 1 invocation, to prove the runtime didn't hang on one
  # failed invocation without a request_id
  n_responses > 1
})