[lit-testing]: ssr fixtures unable to render iterables

Which package(s) are affected?

SSR (@lit-labs/ssr)

Description

When I use an iterable like an array in Lit SSR Web Test Runner plugin, I get the following error:

Error: invalid template strings array
    at N (file:///Users/konnor/projects/lit-ssr-global-xjrrzs/node_modules/lit-html/node/lit-html.js:6:836)
    at U (file:///Users/konnor/projects/lit-ssr-global-xjrrzs/node_modules/lit-html/node/lit-html.js:6:1535)
    at getTemplateOpcodes (file:///Users/konnor/projects/lit-ssr-global-xjrrzs/node_modules/@lit-labs/ssr/lib/render-value.js:119:31)
    at renderTemplateResult (file:///Users/konnor/projects/lit-ssr-global-xjrrzs/node_modules/@lit-labs/ssr/lib/render-value.js:454:17)
    at renderTemplateResult.next (<anonymous>)
    at renderValue (file:///Users/konnor/projects/lit-ssr-global-xjrrzs/node_modules/@lit-labs/ssr/lib/render-value.js:409:16)
    at renderValue.next (<anonymous>)
    at renderValue (file:///Users/konnor/projects/lit-ssr-global-xjrrzs/node_modules/@lit-labs/ssr/lib/render-value.js:427:24)
    at renderValue.next (<anonymous>)
    at renderTemplateResult (file:///Users/konnor/projects/lit-ssr-global-xjrrzs/node_modules/@lit-labs/ssr/lib/render-value.js:476:24)

Reproduction

https://github.com/KonnorRogers/lit-ssr-iterable-bug-reproduction

Workaround

None that ive found, besides manually iterating and creating nodes.

Is this a regression?

No or unsure. This never worked, or I haven't tried before.

Affected versions

3.2.0

Browser/OS/Node environment

➜  lit-ssr-global-xjrrzs git:(main) npm ls lit
node-starter@0.0.0 /Users/konnor/projects/lit-ssr-global-xjrrzs
├─┬ @lit-labs/ssr-client@1.1.7
│ └── lit@3.2.0 deduped
├─┬ @lit-labs/ssr@3.2.2
│ └── lit@3.2.0 deduped
├─┬ @lit-labs/testing@0.2.4
│ └── lit@3.2.0 deduped
└── lit@3.2.0

Node 20.9.0 MacOS 14.5 Browser N/A Web Test Runner: 0.18.3

lit / lit

[lit-testing]: ssr fixtures unable to render iterables #4739