fix: tests + how to write them

2026-05-07 23:22:32 -04:00
parent 899504f8e2
commit c9980b0dca
6 changed files with 194 additions and 56 deletions
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+# Writing Tests
+
+This project uses [Vitest](https://vitest.dev/) for both unit/integration tests and browser tests. There are two separate configs — each targets a different set of files.
+
+## Unit tests
+
+**Config:** `vitest.config.ts`  
+**Runs in:** jsdom (simulated DOM, no real browser)  
+**File pattern:** `src/**/*.test.ts` — anything that does **not** end in `.browser.test.ts`  
+**CI command:** `npm run test`
+
+Use unit tests for pure logic, utility functions, data transformations, and anything that doesn't need real browser APIs (Canvas, WebCodecs, MediaRecorder, etc.).
+
+### File placement
+
+Co-locate the test file next to the source file, or put it in a `__tests__/` folder in the same directory.
+
+```
+src/lib/compositeLayout.ts
+src/lib/compositeLayout.test.ts        # co-located
+
+src/i18n/__tests__/tutorialHelpTranslations.test.ts  # grouped
+```
+
+### Example
+
+```ts
+import { describe, expect, it } from "vitest";
+import { computeCompositeLayout } from "./compositeLayout";
+
+describe("computeCompositeLayout", () => {
+  it("anchors the overlay in the lower-right corner", () => {
+    const layout = computeCompositeLayout({
+      canvasSize: { width: 1920, height: 1080 },
+      screenSize: { width: 1920, height: 1080 },
+      webcamSize: { width: 1280, height: 720 },
+    });
+
+    expect(layout).not.toBeNull();
+    expect(layout!.webcamRect!.x).toBeGreaterThan(1920 / 2);
+    expect(layout!.webcamRect!.y).toBeGreaterThan(1080 / 2);
+  });
+});
+```
+
+### Path aliases
+
+The `@/` alias resolves to `src/`. Use it for imports that would otherwise need long relative paths.
+
+```ts
+import { SUPPORTED_LOCALES } from "@/i18n/config";
+```
+
+### Running locally
+
+```bash
+npm run test          # run once
+npm run test:watch    # watch mode
+```
+
+---
+
+## Browser tests
+
+**Config:** `vitest.browser.config.ts`  
+**Runs in:** real Chromium via Playwright (headless)  
+**File pattern:** `src/**/*.browser.test.ts`  
+**CI commands:** `npm run test:browser:install` then `npm run test:browser`
+
+Use browser tests when the code under test depends on real browser APIs that jsdom doesn't implement: `VideoDecoder`, `VideoEncoder`, `MediaRecorder`, `OffscreenCanvas`, `WebGL`, etc.
+
+### File placement
+
+Name the file `<subject>.browser.test.ts` and place it next to the source file.
+
+```
+src/lib/exporter/videoExporter.ts
+src/lib/exporter/videoExporter.browser.test.ts
+```
+
+### Loading fixture assets
+
+Static assets (video files, images) live in `tests/fixtures/`. Import them with Vite's `?url` suffix so Vite serves them through the dev server.
+
+```ts
+import sampleVideoUrl from "../../../tests/fixtures/sample.webm?url";
+```
+
+### Example
+
+```ts
+import { describe, expect, it } from "vitest";
+import sampleVideoUrl from "../../../tests/fixtures/sample.webm?url";
+import { VideoExporter } from "./videoExporter";
+
+describe("VideoExporter (real browser)", () => {
+  it("exports a valid MP4 blob from a real video", async () => {
+    const exporter = new VideoExporter({
+      videoUrl: sampleVideoUrl,
+      width: 320,
+      height: 180,
+      frameRate: 15,
+      bitrate: 1_000_000,
+      wallpaper: "#1a1a2e",
+      zoomRegions: [],
+      showShadow: false,
+      shadowIntensity: 0,
+      showBlur: false,
+      cropRegion: { x: 0, y: 0, width: 1, height: 1 },
+    });
+
+    const result = await exporter.export();
+
+    expect(result.success, result.error).toBe(true);
+    expect(result.blob).toBeInstanceOf(Blob);
+  });
+});
+```
+
+### Timeouts
+
+Browser tests have a default timeout of 120 seconds per test and 30 seconds per hook (set in `vitest.browser.config.ts`). Export operations are slow — prefer small fixture dimensions (320×180) and low bitrates to keep tests fast.
+
+### Running locally
+
+First install the browser (one-time):
+
+```bash
+npm run test:browser:install
+```
+
+Then run the tests:
+
+```bash
+npm run test:browser
+```
+
+---
+
+## Choosing the right type
+
+| Situation | Use |
+|---|---|
+| Pure function / data transformation | Unit test |
+| i18n key coverage | Unit test |
+| React hook logic (no real browser APIs) | Unit test |
+| `VideoDecoder` / `VideoEncoder` / `MediaRecorder` | Browser test |
+| `OffscreenCanvas` / WebGL / Pixi.js rendering | Browser test |
+| File export producing a real `Blob` | Browser test |