chore: Add test coverage configuration and documentation for component tests

Author: spences10

packages/sveltekit-embed/.gitignore

@@ -11,3 +11,4 @@ vite.config.js.timestamp-*
 vite.config.ts.timestamp-*
 .vercel
 .env*.local
+/coverage

packages/sveltekit-embed/package.json

@@ -27,6 +27,7 @@
 		"check:watch": "svelte-kit sync && svelte-check --tsconfig ./tsconfig.json --watch",
 		"lint": "prettier --check . && eslint .",
 		"format": "prettier --write .",
+		"coverage": "pnpm exec vitest run --coverage",
 		"test:integration": "playwright test",
 		"test:unit": "vitest",
 		"test:ci": "vitest run"
@@ -54,6 +55,7 @@
 		"@sveltejs/package": "^2.3.11",
 		"@sveltejs/vite-plugin-svelte": "^5.0.3",
 		"@vitest/browser": "^3.1.4",
+		"@vitest/coverage-v8": "3.1.4",
 		"eslint": "^9.27.0",
 		"eslint-config-prettier": "^10.1.5",
 		"eslint-plugin-svelte": "^3.9.0",

packages/sveltekit-embed/vite.config.ts

@@ -1,5 +1,6 @@
 import { sveltekit } from '@sveltejs/kit/vite';
 import { defineConfig } from 'vite';
+import { coverageConfigDefaults } from 'vitest/config';
 
 export default defineConfig({
 	plugins: [sveltekit()],
@@ -35,5 +36,23 @@ export default defineConfig({
 				},
 			},
 		],
+		coverage: {
+			all: true,
+			reporter: ['text-summary', 'html'],
+			exclude: [
+				...coverageConfigDefaults.exclude,
+				'**/config.{js,ts,cjs}',
+				'**/*.config.{js,ts,cjs}',
+				'**/e2e/**',
+				'**/lib/index.ts',
+				'**/routes/page.svelte',
+			],
+			thresholds: {
+				statements: 80,
+				branches: 65,
+				functions: 80,
+				lines: 80,
+			},
+		},
 	},
 });