[jira] [Closed] (ARROW-14458) [R] Use expect_snapshot() to improve tests

["Dragoș Moldovan-Grünfeld (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ARROW-14458?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Dragoș Moldovan-Grünfeld closed ARROW-14458.
--------------------------------------------
    Resolution: Later

> [R] Use expect_snapshot() to improve tests
> ------------------------------------------
>
>                 Key: ARROW-14458
>                 URL: https://issues.apache.org/jira/browse/ARROW-14458
>             Project: Apache Arrow
>          Issue Type: Improvement
>          Components: R
>            Reporter: Dragoș Moldovan-Grünfeld
>            Assignee: Dragoș Moldovan-Grünfeld
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 9.0.0
>
>          Time Spent: 8h 10m
>  Remaining Estimate: 0h
>
> Update (2022, January 20):
> [Hadley's suggestion|https://github.com/r-lib/testthat/issues/1471#issuecomment-1005372257] would be to move away from the
> {code:r}
> expect_snapshot({
>   (expect_error())
> }) 
> {code}
> pattern and use one of 3 options:
>  
>  * If you want to inspect the error message, use {{{}expect_snapshot(error = TRUE){}}}.
>  * If you want to check the class, use {{expect_error(class = )}}
>  * If you want to expect the message and check the class, use {{{}expect_snapshot_error(class = ){}}}.
> I have being using option 1 and it seems to do most of what we want. For example, see the [left_join by arg PR|https://github.com/apache/arrow/pull/12179].
> ==============
> This comes from [Romain's suggestion|https://github.com/apache/arrow/pull/11502/files/2a8a139b727acb13019da6176444578ead6bf208#r735351673] to transform the test that rely on capturing a string by using a snapshot test (added in {{{}testthat{}}}'s 3rd edition).
> A test like:
> {code:r}
> expect_error(expression, message)
> {code}
> becomes
> {code:r}
> expect_snapshot({
>   (expect_error(expression))
> })
> {code}
> This is probably a more general improvement we can make to our unit tests (i.e. to make more extensive use of the snapshot functionality), but I thought I'd focus on one test file to begin with.



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