The Testing Philosophy

Lykn doesn’t reinvent the test runner. Deno already has discovery, parallel execution, watch mode, filtering, coverage, and four reporters. What Deno doesn’t have is a way to write tests in s-expression syntax with keyword clauses and assertion forms that feel like the rest of the language. That’s the gap.

What `lykn test` Does

Two phases. That’s the whole thing.

Discover *_test.lykn and *.test.lykn files
Compile them to .js
Invoke deno test on the compiled output
Report Deno’s exit code

The Rust compiler handles compilation. Deno handles execution, parallelism, reporters, coverage, sanitizers, and everything else a test runner should do. lykn test is the thin glue between them.

What the Macros Do

The testing DSL lives in packages/testing/ — a macro module, not a compiler feature. The macros test, suite, step, and the assertion forms expand to Deno.test() + jsr:@std/assert calls at compile time. The compiled output is standard Deno test code. A developer who reads the generated JavaScript would recognise it immediately.

(import-macros "testing" (test is-equal))

(test "addition works"
  (is-equal (+ 1 2) 3))

import { assertEquals } from "jsr:@std/assert";

Deno.test("addition works", () => {
  assertEquals(1 + 2, 3);
});

No runtime dependency. No custom test runner. No framework. Just macros that erase themselves and leave clean, portable JavaScript behind — which is, if you think about it, the politest thing a testing framework can do.

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