RS-21803: Banded Rows test

[SurreyHughesDisplayr]

Summary

Adds unit test coverage for the banded.rows and banded.cols arguments of CreateCustomTable (R/createcustomtable.R).

• Pins each banding rule as one contiguous exact string — both the odd and even clauses and both fill values — so inserting anything between the clauses, or swapping banded.odd.fill with banded.even.fill, fails the test.
• Asserts no nth-child rule is emitted at all when banding is off.
• Pins the column rule verbatim, including the td:nth-child(2n+3) / td:nth-child(even) pair as coded.
• Asserts a cell-level fill suppresses the banded background, as a single-variable contrast against the unbanded case.
• Asserts the banding rule is emitted once regardless of row count.
• Extracts the generated container id and asserts the odd clause is scoped to it, guarded by expect_length(containerSel, 1) so the assertion cannot pass on an empty match.

Pinned production defect

The second clause of each banding rule is emitted without the container prefix — ;} tr:nth-child(even) for rows and ;} td:nth-child(even) for columns — so it is not scoped to this table and leaks to every table on the page. Both halves are pinned as current behaviour and will fail when the scoping is fixed. Genuine defect, no ticket filed.

Plan corrections

Two of the plan's expectations did not survive checking and were corrected rather than encoded:

• The plan's example CSS strings have no space before ;. cata() writes via cat(..., sep = " "), so real output is background-color: rgb(250,250,250) ; — the plan's string never occurs. Tests pin the real text.
• The plan records the 2n+3 / even column selectors as overlapping and asks for that to be logged as a defect. They are provably disjoint: 2n+3 = {3, 5, 7, …} and even = {2, 4, …}. With row headers shown the header cell occupies nth-child(1), so data columns land on 2, 3, 4 and alternate correctly. Not a defect. (One genuine gap the plan did not raise: with show.row.headers = FALSE, column 1 matches neither selector and is left unbanded. Noted in a comment, not asserted.)

Jira: https://numbers.atlassian.net/browse/RS-21803

Stacked PR

Based on RS-21803-rowspans (#68), not master — these plans all add tests to tests/testthat/test-createcustomtable.R and share its helpers. Merge order: #66, #67, #68, then this. The diff against that base is this plan's work only.

Test plan

Rscript -e "devtools::load_all('.'); testthat::test_file('tests/testthat/test-createcustomtable.R')"

137 passing, 0 failures, 0 warnings.

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