Test Strategy#

The suite protects the package's actual product boundary: valid code commonly published in blogs and documentation, with a small browser payload and synchronous client performance.

Contracts#

• Every supported language has representative fixtures. Languages available in TanStack Markdown or MDX files also have committed samples from those docs.
• The corpus contains up to twenty samples per language and currently totals 334 blocks.
• Every token stream reconstructs its source byte for byte.
• Focused regressions cover context-sensitive failures such as TSX generics, nested template interpolation, regular expressions, Python triple strings, shell heredocs, YAML fragments and block scalars, and markup embeddings.
• HTML uses one escaped <pre><code> tree with no inline style attributes.
• Unknown languages fall back to plaintext.
• Remark and rehype produce structured nodes and do not require raw HTML.
• Every public ESM subpath imports directly from the packed package shape.

Size Profiles#

pnpm run size checks seventeen independent browser profiles, including root helpers, language barrel imports, adapters, and themes. Each has minified, gzip, and Brotli budgets. The main highlighter profiles are:

The selective profiles are the primary product metric. The all-language profile protects the convenience entry from unbounded growth. Bundle graphs reject unexpected language or theme code. Package tests repeat isolation checks through public exports after building.

Throughput#

pnpm run bench measures highlighting, tokenization, Markdown, HAST, line numbers, long numbered blocks, long decorated blocks, and dedicated C++, CMake, and PHP samples. Timings use the median of three samples after two warmup passes. Each profile has a 1.2 second CI budget; the main highlighting profile processes at least 10,000 blocks.

pnpm run compare:sugar-high compares the overlapping JS/TS/JSX/TSX use case. pnpm run compare:shiki compares all supported fixtures. These are directional measurements, not claims of equivalent grammar depth.

Deliberate Omissions#

The package does not maintain compiler conformance suites, malformed-input fuzzing, ReDoS corpora, editor state tests, or exact parity snapshots against another highlighter. Those would optimize for a broader parser product than this library intends to become.