# mdcat stress test — every element, most gnarly combinations
This document is an intentional kitchen-sink to make sure the renderer
handles every CommonMark + GFM construct mdcat supports, plus the
typically gnarly combinations: deep nesting, wide content, Unicode,
emoji, ANSI-breaking text, and ASCII diagrams.
## Heading levels
# H1 — top level
## H2 — second level
### H3 — third level
#### H4 — fourth level
##### H5 — fifth level
###### H6 — sixth level
Headings with inline formatting: `code`, **bold**, _italic_, and
[a link](https://example.com/) should all survive.
## Inline markup
Plain paragraph with **bold**, *italic*, `inline code`, ~~strikethrough~~,
and ***bold italic***. Also **_bold with italic inside_** and
`code with **ignored** markup`.
Long words and URLs stress the wrapper:
https://example.com/a/very/long/path/that/does/not/break/nicely/until/way/past/eighty/columns.html
Soft wrapped line —
with a hard break before this one, using two trailing spaces.
Unicode essentials: café, naïve, straße, μέλλον, 漢字, العربية, עברית, 🧪🚀✨.
Combining marks and ZWJ: é (U+0065 U+0301), 👨👩👧👦, 🏳️🌈.
## Links and references
Inline link: [mdcat on GitHub](https://github.com/swsnr/mdcat "Title here").
Reference link: [crates.io][cratesio] and again [crates.io][cratesio].
Autolink: <https://example.org/auto>. Email: <hello@example.org>.
Relative link: [README](./README.md) should become a `file://` URL.
[cratesio]: https://crates.io/crates/mdcat "See releases"
## Blockquotes
> Single-line quote.
> Multi-line quote that wraps nicely when the line is long enough
> to exceed the terminal width so we can see the bar appear on
> every wrapped line, including this third physical line.
>
> Second paragraph still inside the quote.
> Quote with **bold**, *italic*, `code`, and [a link](https://example.com/).
> Nested quotes:
>
>> inner quote with its own *emphasis*.
>>
>>> third level should still resolve, even if the bar doesn't nest.
## Lists
Unordered:
* level 1
* level 2 with **bold**
* level 3 with `code`
* level 4 with a long sentence that has to wrap to demonstrate
that list-item wrapping respects the current indent level
and nests cleanly.
* another top-level item
Ordered:
1. first
2. second
1. second-first
2. second-second
- mixed unordered inside ordered
- [ ] task item unchecked
- [x] task item checked
3. third with a blockquote:
> the quote lives inside the list item
4. fourth with a code block:
```rust
fn hello() {
println!("from inside a list item");
}
```
5. fifth with a *nested paragraph*
Second paragraph of the list item. It should stay indented under
the bullet.
Task list at top level:
- [ ] Unchecked todo
- [x] Done with `code` in it
- [ ] ~~Scratched-out~~ work
- [x] Bold task **matters**
## Code blocks
Fenced with language:
```rust
/// A doc comment — syntect should colour me.
pub fn fibonacci(n: u64) -> u64 {
match n {
0 | 1 => n,
_ => fibonacci(n - 1) + fibonacci(n - 2),
}
}
fn main() {
for i in 0..10 {
println!("fib({i}) = {}", fibonacci(i));
}
}
```
```python
# Python with unicode, long line, and a trailing newline.
def greet(name: str) -> None:
print(f"Hello, {name}! 🎉 — this line is intentionally long enough to exceed eighty columns so we see wrapping or truncation behaviour")
greet("world")
```
```bash
#!/usr/bin/env bash
set -euo pipefail
# A loop with a very long line embedded as a comment to test wrapping inside a highlighted block.
for i in 1 2 3; do echo "$i"; done
```
```json
{
"name": "mdcat",
"version": "3.0.0-alpha.0",
"keywords": ["markdown", "terminal", "renderer"],
"features": {
"sixel": true,
"kitty-graphics": true,
"iterm2-images": true
}
}
```
Fenced without a language (no syntect):
```
plain code
with weird whitespace
and a trailing
newline
```
Fenced with an unknown language (still a code block, but no highlighting):
```brainfuck
++++++++[>++++[>++>+++>+++>+<<<<-]>+>+>->>+[<]<-]>>.>---.+++++++..+++.>>.<-.<.+++.------.--------.>>+.>++.
```
Indented code block (four-space):
indented code does not have fence or language
but should still get the code styling and box
Empty code block (should still render):
```
```
## Tables
Simple:
| Headings | ✅ | All six levels |
| Lists | ✅ | Task lists included |
| Images | ⚠️ | Terminal-dependent |
| Alerts | ✅ | GFM blockquotes |
Alignment:
| a | b | c |
| long | center | 99 |
| thing | x | 42 |
Wide table that must truncate:
| toc | Indented bullets, one heading per line with `* ` | NDJSON with `{"level":N,"text":"...","anchor":"..."}` fields | `--depth N` caps at level |
| slice | Raw markdown of the requested section | N/A — use `--render` to pipe through the normal renderer | `--all` emits every match |
| links | `URL\tTITLE` per line | NDJSON `{url,title,text,kind}` | `--unique` dedupes |
Single-column edge case:
| one |
| two |
## Horizontal rules
Before:
---
After, with asterisks:
***
And with underscores:
___
## HTML passthrough
Inline HTML: a plain <em>em</em> and <strong>strong</strong> tag, plus a
<code>code</code> span in angle brackets.
Block HTML:
<div class="note">
<p>This is raw HTML and mdcat prints it verbatim with a distinct style.</p>
<p>Multi-line should still align with the block's indent.</p>
</div>
## ASCII diagrams
A tree:
```
mdcat/
├── src/
│ ├── main.rs # CLI entry
│ ├── lib.rs # library + process_file
│ ├── render/
│ │ ├── blocks.rs # paragraphs, headings, rules
│ │ ├── code.rs # code blocks with the │ bar
│ │ ├── tables.rs # unicode box tables
│ │ └── images.rs # iTerm2 / Kitty / Sixel dispatch
│ └── terminal/
│ ├── detect.rs # env-var based detection
│ ├── probe.rs # DA1 sixel probe
│ └── multiplexer.rs
└── tests/
├── render.rs # snapshot tests
└── cli.rs # CLI integration
```
A sequence diagram:
```
User mdcat Terminal
│ │ │
│ mdcat file.md │ │
│ ────────────────▶ │ │
│ │ detect capabilities │
│ │ ───────────────────▶ │
│ │ ◀─────────── Kitty, │
│ │ sixel, │
│ │ osc8 │
│ │ push_tty(events) │
│ │ ─────────────────▶ │
│ │ │
│ │ image escape │
│ │ ◀──── wraps in tmux │
│ │ DCS if $TMUX │
│ ◀──── rendered │ │
│ output │ │
```
A box diagram:
```
╔══════════════════╗ ╔═══════════════════╗
║ pulldown-cmark ║────▶║ render state ║
║ Event stream ║ ║ machine ║
╚══════════════════╝ ╚═══════════════════╝
│
▼
╔═══════════════════╗
║ terminal writer ║
╚═══════════════════╝
```
A flowchart:
```
┌──────────┐ no ┌──────────────┐
│ is TTY? │──────▶│ Dumb (text) │
└────┬─────┘ └──────────────┘
│ yes
▼
┌──────────┐
│ --ansi? │──yes─▶ Ansi
└────┬─────┘
│ no
▼
┌──────────┐
│ detect() │──▶ iTerm2 / Kitty / Sixel / …
└──────────┘
```
## Images
PNG:
SVG:
Remote (requires network):
Image inside a list:
1. First step
2. Look at this:
3. Third step
## Pathological edge cases
Consecutive hard breaks:
one
two
three
Backtick salad: ``` nested ``backticks`` inside ``` a span, plus a lone `.
A super long word that absolutely cannot be split anywhere:
supercalifragilisticexpialidocioussupercalifragilisticexpialidocioussupercalifragilisticexpialidocious
A paragraph containing the literal string `ESC[31m` should not colour the
rest of the page red — the library must quote or strip raw ANSI in user
text.
## Closing thoughts
If every heading, quote, list, code block, table, diagram, image, and
inline run above looked right, we're in good shape. Any visual oddities
here are a bug.
