docs: testing + docs

website/src/pages/technical-manual/testing.mdx

@@ -0,0 +1,27 @@
+---
+title: Testing
+layout: ../../layouts/MainLayout.astro
+---
+
+# Testing
+
+Strudel uses [vitest](https://vitest.dev/) for testing, with 2 types of testing strategies:
+
+- unit tests for fine grained testing
+- automated snapshot tests for broader testing
+
+## Unit Tests
+
+Each package has a `test` folder where tests are written on a file by file basis, e.g. `util.test.mjs` implements all tests for `util.mjs`.
+
+## Snapshot Tests
+
+Snapshot tests allow testing larger chunks of data. Strudel uses snapshot tests for:
+
+- Example Snippets: `examples.test.mjs`, using snippets under `@example` inside jsdoc comments
+- Example Tunes: `tunes.test.mjs`, using all patterns in `tunes.mjs`
+
+The snapshot (`.snap`) files contain all haps within a certain number of cycles for each tested pattern.
+They allow testing for breaking changes on a larger scale.
+If breaking changes are intentional, the snapshots can be updated with `npm run snapshot`.
+Just make sure to verify that all affected patterns behave as expected.