What "verified" means
Every reference page carries one of two badges. They are not marketing labels — they describe exactly how much of that page a test suite is holding up, and they are worth understanding before you trust a number.
verified
The algorithm's arithmetic is asserted against the worked example published in its article. The package, the article and the standalone repository agree on the numbers, and CI fails if they stop agreeing.
Concretely: the article works an example through by hand, that example is stored as a machine-readable fixture, and the conformance suite replays it on every run. If someone changes the implementation so it produces a different answer, the build goes red.
79 of 187 topics are in this tier.
contract
The module loads, its declared entry function exists and is callable, its registry metadata matches reality, and its exports are what the package claims. What is not asserted is the arithmetic: no published numbers exist in the catalog for this topic yet, so nothing checks that the answer is right.
108 of 187 topics are in this tier.
This is stated plainly rather than hidden, because the alternative — implying uniform confidence across 187 topics — would be worse. Most libraries in this space assert nothing at all and say nothing about it.
Where the examples come from
Separately from the badge, every page shows a worked example. There are three sources, and each page says which one it used:
| Origin | What it is |
|---|---|
| fixture | The published { input, expected } from the article. Asserted by the test suite — this output cannot drift. |
| executed | The arguments the algorithm's own test passes it, and what the function actually returned when run. Real output of real code, not asserted against the article. |
| derived | The same, for thin wrappers a test never calls directly: the entry is invoked with the arguments its shared sibling received. |
No example on this site was typed by hand. Every one is the output of running the code. What differs between them is whether an independent published source says that output is correct.
Long inputs and outputs are abbreviated for readability, and the page says how much was elided — "6 of 160 shown" — rather than quietly truncating.
How the gap gets closed
Moving a topic from contract to verified means adding machine-readable expected values to the catalog: an input, and the numbers the article already works through in prose. It is authoring work rather than engineering, and it happens steadily.
If you find a wrong answer, the most useful thing you can send is the input and the value you expected. That becomes a fixture, and a fixture is what turns a contract badge into a verified one — for everyone.