Sometimes your tests using a vcr cassette will fail and you will want to debug them.
If you get an error starting with “An HTTP request has been made that vcr does not know how to handle:” when running your tests, it means that the code in your test makes an HTTP request for which there is no matching information in the cassette you are using. You might have added a request, or changed one slightly.
The easy fix is: delete the cassette and re-run the test to re-record the cassette. Run the test a second time to ensure all is well. If not, escalate to the next paragraph.
Maybe you didn’t actually want to change the request you are making.
Make sure the requests do not contain something random, or something
related to e.g. what time it is now, in the URI
(http://foo.com?time=13). To make sure things are not
varying, you might want to use mocking (of e.g. a function returning the
current time), setting a random seed, using withr (for e.g. setting
an option to a certain value in your test).
Ideally you will want to run the code of the tests as if it were run inside tests, in particular, using the same vcr cassette.
You will first need to load either the vcr helper
tests/testthat/helper-vcr.R (e.g. via
devtools::load_all()) or source the vcr setup file
tests/testthat/setup-vcr.R i.e. the file with these lines
(and maybe others)
library("vcr")
invisible(vcr::vcr_configure(
dir = vcr::vcr_test_path("fixtures"),
filter_sensitive_data = list("<<github_api_token>>" = Sys.getenv('GITHUB_PAT'))
))
vcr::check_cassette_names()If instead of vcr::vcr_test_path("fixtures") you see
"../fixtures", replace "../fixtures" with
vcr::vcr_test_path("fixtures"), as
vcr::vcr_test_path() is a function that is meant to help
exactly what you will want: have the path to
tests/fixtures/ work from tests and from the root (which is
where you will be running the code to debug it).
So that is one step (loading the vcr helper or sourcing the vcr setup
file), or maybe two (if you also had to replace
"../fixtures" with
vcr::vcr_test_path("fixtures")).
Now look at the test whose code you are trying to debug e.g.
foo <- function() crul::ok('https://httpbin.org/get')
test_that("foo works", {
vcr::use_cassette("testing", {
x <- foo()
})
expect_true(x)
})If you want to run the code as if you were in the test,
You can use vcr’s built in logging to help in your debugging process.
To configure logging, use the vcr_configure() function, and
set log=TRUE and set options for logging on the
log_opts parameter as a named list. See
?vcr_configure for details.
Here, we are setting our log file to be a temporary file that will be
cleaned up at the end of the R session. Here, the file extension is
.log, but the file extension does not matter.
vcr::vcr_configure(
dir = vcr::vcr_test_path("fixtures"),
log = TRUE,
log_opts = list(file = file.path(tempdir(), "vcr.log"))
)With log=TRUE you can continue with debugging. Open the
log file you set in a text editor or other location; or examine in your
shell/terminal.
As an example, after running the block above
foo <- function() crul::ok('https://httpbin.org/get')
test_that("foo works", {
vcr::use_cassette("testing", {
x <- foo()
})
expect_true(x)
})If we open the log file we’ll see the logs for each step vcr takes in handling an HTTP request. The logs have information on what cassette was used, what exact time it was recorded, what matchers were in use, the cassette options, and how a request is handled.
[Cassette: 'testing'] - 2020-11-24 16:05:17 - Init. HTTPInteractionList w/ request matchers [method, uri] & 0 interaction(s): { }
[Cassette: 'testing'] - 2020-11-24 16:05:17 - Initialized with options: {name: testing, record: once, serialize_with: yaml, persist_with: FileSystem, match_requests_on: c("method", "uri"), update_content_length_header: FALSE, allow_playback_repeats: FALSE, preserve_exact_body_bytes: FALSE}
[Cassette: 'testing'] - 2020-11-24 16:05:17 - Handling request: head https://httpbin.org/get (disabled: FALSE)
[Cassette: 'testing'] - 2020-11-24 16:05:17 - Identified request type: (recordable) for head https://httpbin.org/get
[Cassette: 'testing'] - 2020-11-24 16:05:17 - Recorded HTTP interaction: head https://httpbin.org/get => 200 Logging isn’t meant to be turned on all the time - rather only for debugging/informational purposes.
Make sure you ejected the cassette you were using!
Unless your vcr helper/setup file tweaked more things than you would like, you do not even need to re-start R, but you could, just to be on the safe side.