test: cover the eleven components we wrote that nothing tested

[IgorShevchik]

Linked issue

Refs #86 — one slice of it, not the whole inventory.

Type of change

• Documentation (updates to the documentation or readme)
• Bug fix (a non-breaking change that fixes an issue)
• Enhancement (improving an existing functionality)
• New feature (a non-breaking change that adds functionality)
• Chore (updates to the build process or auxiliary tools and libraries)
• Revert (undoing a merged change — retitle this PR revert(Scope): ...)
• Breaking change (fix or feature that would cause existing functionality to change)

How the slice was chosen

#86 lists everything untested. Re-measured, its June figures have moved — 66 components without a spec of their own rather than 76, 13 untested composables rather than 19, and tv.ts, which the issue calls out as "the theme merge engine!", has had a spec for a while.

The measure that mattered was different: 68 components are imported by no spec at all, and of those, all but thirteen exist in nuxt/ui@v4 — where they have no specs either. Writing those would be testing somebody else's code twice, in a file we re-sync from them. The thirteen that are ours have no coverage anywhere.

Eleven are covered here. ModalDialogClose is left out: a nineteen-line DialogClose passthrough that needs a dialog around it before it can say anything.

	lines	what it gets
PageCardGroup	377	selection, key mapping, grouping, colour fallback, axe, snapshots
SidebarLayout	275	loading state, slot-driven regions, axe, snapshots
SidebarBody/Footer/Header/Heading/Section/Spacer	~55 each	the as / class / slot contract
Navbar	58	landmark element, composition, axe, snapshots
NavbarDivider/Section/Spacer	~57 each	the as / class contract

Two defects found while writing them

SidebarLayout rendered its data-state as a literal string. The binding was written without its colon:

data-state="isLoading ? 'loading' : 'show'"

so every layout put the source of the expression into the DOM instead of its value, always. It is the only unbound data-state in src/runtime/components. Fixed, with a test that reddens when the colon is removed again.

offContentScrollbar is a public prop that does nothing. Both branches of its variant in src/theme/sidebar-layout.ts are empty strings, and the one compound that reads it has its entire class block commented out:

offContentScrollbar: { false: '', true: '' },
…
{ inner: true, offContentScrollbar: false, class: {
    // pageWrapper: 'scrollbar-thin scrollbar-transparent overflow-y-scroll'
} }

Not fixed here. Restoring those classes or removing the prop is a decision about public API shape, not a test change. No case is added for it either — one would be byte-identical to with isInner and would read as coverage of a prop that does not work.

Three things in the specs worth copying

• Only useRoute is mocked in SidebarLayout.spec.ts, not the router. Installing one fails the other project every time: the nuxt project has none, so useRoute() warns about a missing injection on every mount; the vue project's shim already installs one, so a second plugin re-registers RouterLink. Each project's fix is the other's console-gate failure.
• Element assertions read through [data-slot="root"]. A template that opens with an HTML comment renders as a fragment, and wrapper.element is then Vue Test Utils' own wrapper. Navbar looked like it rendered a div until that was accounted for — the component was fine, the assertion was not.
• The generated size and columns matrices skip the default value, because a case for it is byte-identical to with items (test: fourteen specs assert a default because the fixture never reaches the branch #454).

What the #454 guard caught in the first draft

Three cases that asserted nothing, and it was right about all three: two default-valued variants of PageCardGroup, and a SidebarLayout fixture too thin for useLightContent to have any content to shape. Fixed by narrowing the matrices and giving the fixture a slot, not by regenerating the baseline — the baseline is unchanged.

Mutation-checked throughout. Where a claim could not be made to fail — categoryKey: '' short-circuits to the same output as looking the empty key up, and icon-over-avatar is enforced twice, in getItemAvatar and again in PageCard — the spec says so instead of carrying a test that cannot go red.

Gate

lint, typecheck, 328 test files / 7618 tests, test:module, and coverage 71.89 → 74.31% statements, 69.93 → 71.53 branches, 71.19 → 73.35 functions, 71.44 → 73.80 lines, against thresholds of 70 / 68 / 70 / 70.

Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

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