Creating a Single-Sprite Variant

Overview

A single-sprite asset-generation test case (asset_kind = "sprite", the default) draws one sprite onto the whole canvas to match a written brief. Its version offers one or more variants, and a run selects exactly one. Every variant seeds the version’s common specs plus its own additive specs. The chosen variant’s slug is recorded in the run record, so every result is attributed to a specific build.

This guide is the procedure for adding a variant to an existing single-sprite version. The authoritative rules live in Sprite cases and the Manifests overview.

Variant scope

An asset-generation case has no target image and declares no [[reference]]; resolution rejects any reference, common or per-variant. A variant therefore has nothing to repoint: the model draws to match the brief.

What a variant varies is the brief itself, through an additive spec: a tighter palette, a stricter operation budget, a required drawing technique such as flat fills only, or another stylistic constraint. A genuinely different subject is a new case rather than a variant.

The asset_kind and the [canvas] are version-level, so every variant draws the same size sprite.

An asset-generation case declares no reviewer checklist. The sprite is judged as a whole against the brief it was seeded with, on the case’s single overall domain (see Judged on one overall rating). The variant brief is therefore the only place its constraint is recorded, so write it precisely enough that a reviewer can weigh it.

Procedure

1. Choose the variation

Decide the constraint the variant imposes and keep it consistent everywhere:

• slug, lowercase, used in test-case.toml and the spec filename, such as flat;
• display name, title case, the variant’s name, such as Flat Shading;
• description, one line naming the constraint.

Favor a single constraint a reviewer can observe in the regenerated sprite.

2. Write the variant brief

Create specs/<slug>.md, stated as a delta against the common brief:

• open by stating which common brief it builds on, by name;
• state the added or tightened constraint in precise, testable terms: exact colors, an operation cap, the technique required;
• reaffirm that it draws to match the same brief, with only the added constraint changing.

A variant spec may reference the common specs freely, since they are always seeded, and must never reference another variant’s spec.

3. Create the variant file and list it

Write variants/<slug>.toml as a standalone TOML document whose top-level keys are the variant’s fields, then add its path to the variants array in test-case.toml. The first entry is the default. Paths inside resolve against the version folder, and dest defaults to source.

variants/flat.toml

slug = "flat"
name = "Flat Shading"
description = "Same brief, drawn with flat fills only rather than gradients or dithering."
spec = [{ source = "specs/flat.md" }]

# test-case.toml: add the new file to the ordered list (first = default)
variants = ["variants/base.toml", "variants/flat.toml"]

What resolution enforces, and what a variant leaves alone:

• spec entries are additive on the common specs. Within one variant, no two seeded specs may share a dest.
• A reference entry is rejected for this test type, on the case and on a variant.
• asset_kind and [canvas] are version-level, so a variant declares neither.
• A variant declares no review items, matching the case.

Update the human-readable comment in the manifest that enumerates the variants so the list stays accurate.

Validate your work

Seed and render the new variant, and re-check the existing ones to confirm your edits changed nothing for them:

tcab seed   --test-case <slug> --version <version> --variant <new-variant>
tcab prompt --test-case <slug> --version <version> --variant <new-variant>

Read the seeded output to confirm the new variant’s brief is self-contained, then lint the specs with npm run lint:specs. If cspell flags a legitimate domain term, add it to .cspell/project-words.txt.

The backend’s definition store is immutable per case version, so force a re-ingest before running:

scripts/reingest.sh --force <slug>

Force re-ingest overwrites the stored version in place and is for development only. Adding a variant edits an existing version, so do it only while that version is unpublished; a version a published run references is frozen and needs a new version instead. Then exercise the variant with Run a Test Case.