Test Organisation

Which file does a test belong in?

Use this skill when adding a test, moving one, or wondering whether a new test file is warranted. The instinct to name a test file after the feature you are working on is wrong here, and it is how the suite drifted out of shape before.

Rule

A test goes in the test file named after the R file that defines the function under test.

A test for calc_selectivity() — defined in R/setFishing.R — belongs in tests/testthat/test-setFishing.R. Not test-calc-selectivity.R, not test-selectivity.R. Find the home before writing the test:

grep -ln "^[ ]*<name> <- function" R/*.R

Do not create a new test file just because a function or a feature is new. Create one only when a new file appears under R/. Conversely, every R file containing logic should have a matching test-<name>.R.

The name must match exactly, including any suffix: R/ArraySpeciesBySize-class.R is tested by test-ArraySpeciesBySize-class.R.

The exception: genuinely cross-cutting tests

Some tests exercise the interplay of functions from several R files and so have no single home. Those live in files named after the functionality they test. This is a small, closed list — do not add to it without good reason:

• test-analytic_results.R, test-analytic_transport.R — rates and transport checked against closed-form solutions
• test-single_species.R — the whole pipeline on a one-species model
• test-second_order_summary.R — summary integrals under the second_order_w flag
• test-backwards_compatibility.R — legacy constructors and R/deprecated.R
• test-reexports.R — package-level re-exports

A test that mostly calls one function is not cross-cutting, even if it needs a projection to set up. Ask which file you would edit if the test failed.

Some R files are deliberately without a test file of their own: deprecated.R (covered by test-backwards_compatibility.R), mizer-package.R (documentation only) and RcppExports.R (generated).

Moving a test between files

Snapshots live in _snaps/<test-file-name-without-the-test--prefix>.md, keyed by the test_that() description. Moving a test means moving its snapshot block to the destination's .md file, or the snapshot is orphaned in one file and missing in the other. vdiffr figures live in _snaps/<name>/ directories the same way.

If the destination file has top-level setup, check the moved test does not depend on objects that only existed in its old file, and that its own top-level objects do not collide with names already there.

When an R file is split

Splitting an R file means splitting its test file the same way, so the correspondence survives. Also add the new file to Collate: in DESCRIPTION (roxygen2 does not manage this in mizer) and re-run devtools::document() — the % Please edit documentation in R/... line of every moved function's .Rd needs regenerating.