capture_requests is a context that collects the responses from requests you make and stores them as mock files. This enables you to perform a series of requests against a live server once and then build your test suite using those mocks, running your tests in with_mock_api().

capture_requests(expr, path, ...)

start_capturing(path = NULL, simplify = TRUE)




Code to run inside the context


Where to save the mock files. Default is the first directory in .mockPaths(), which if not otherwise specified is the current working directory. It is generally better to call .mockPaths() directly if you want to write to a different path, rather than using the path argument.


Arguments passed through capture_requests to start_capturing


logical: if TRUE (default), JSON responses with status 200 will be written as just the text of the response body. In all other cases, and when simplify is FALSE, the "response" object will be written out to a .R file using base::dput().


capture_requests returns the result of expr. start_capturing invisibly returns the path it is given. stop_capturing returns nothing; it is called for its side effects.


start_capturing and stop_capturing allow you to turn on/off request recording for more convenient use in an interactive session.

Recorded responses are written out as plain-text files. By storing fixtures as plain-text files, you can more easily confirm that your mocks look correct, and you can more easily maintain them without having to re-record them. If the API changes subtly, such as when adding an additional attribute to an object, you can just touch up the mocks.

If the response has status 200 OK and the Content-Type maps to a supported file extension---currently .json, .html, .xml, .txt, .csv, and .tsv---just the response body will be written out, using the appropriate extension. 204 No Content status responses will be stored as an empty file with extension .204. Otherwise, the response will be written as a .R file containing syntax that, when executed, recreates the httr "response" object.

If you have trouble when recording responses, or are unsure where the files are being written, set options(httptest.verbose=TRUE) to print a message for every file that is written containing the absolute path of the file.

See also

build_mock_url() for how requests are translated to file paths. And see vignette("redacting") for details on how to prune sensitive content from responses when recording.


if (FALSE) { capture_requests({ GET("") GET("") GET("", query=list(`Content-Type`="application/json")) }) # Or: start_capturing() GET("") GET("") GET("", query=list(`Content-Type`="application/json")) stop_capturing() }