Thanks a ton for using and troubleshooting the development code! It is an enormously valuable and helpful contribution to the project.

Are you willing/able to add tests and attempt to fix?

You're welcome. Thanks for developing it in the first place!

Locally I think I fixed it by just deleting the check I mentioned. I can try to add a test but I need to get to grips with RUnit...

Right, simply deleting that check makes sense. I believe that is left-over from when the function only operated on univariate objects.

I'm not sure what you're doing to 'get to grips with RUnit'... I would hope you could copy and modify one of the existing tests. In this case, you should be able to modify the test I put in the comment to the first issue you opened.

test.nalocf_first_column_all_NA <- function() {
  nacol <- 1L
  for (m in MODES) {
    xdat <- XDAT2
    xdat[,nacol] <- xdat[,nacol] * NA
    storage.mode(xdat) <- m
    zdat <- as.zoo(xdat)

    x <- na.locf(xdat)
    z <- na.locf(zdat)
    checkEquals(x, as.xts(z), check.attributes = TRUE)
  }
}

I'm struggling to work out how to run the tests easily. Any pointers gratefully received.

I can do R CMD build then R CMD check on the tar. That seems to give a different result to evaluating bits of the file in the test directory.

For what it's worth, I trust the results of R CMD build ... && R CMD check ... more than running tests outside of that pattern. Likely because I sometimes forget part(s) of the relevant process for building/installing a package, but also because that's what CRAN does. That said, it would be nice to have something like make test [args] that could run quickly, so you could iterate quickly.

I know RStudio / devtools / testthat have ways to run individual tests, but I have encountered too many instances of users being confused because an updated package didn't load correctly when the package was already loaded in the current session.

One thing you could do is something like this:

Rscript -e 'library(xts); library(RUnit); source("xts/inst/unitTests/runit.na.locf.R"); test.nalocf_last_column_all_NA()`

Sorry I don't have a better answer...