test: add test coverage

Author: ben-challis

.eslintrc.yml

@@ -1,6 +1,7 @@
 env:
   node: true
-  es6: true
+  jest: true
+  es2022: true
 
 globals:
   Atomics: readonly

.github/workflows/test.yml

@@ -0,0 +1,28 @@
+name: Test
+
+on:
+  pull_request:
+  merge_group:
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  test:
+    runs-on: ubuntu-24.04
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version-file: .node-version
+          cache: npm
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Run tests
+        run: npm test

jest.config.mjs

@@ -0,0 +1,13 @@
+export default {
+  preset: 'ts-jest',
+  testEnvironment: 'node',
+  roots: ['<rootDir>/src'],
+  testMatch: ['**/__tests__/**/*.test.ts', '**/?(*.)+(spec|test).ts'],
+  transform: {
+    '^.+\\.ts$': 'ts-jest'
+  },
+  clearMocks: true,
+  resetMocks: true,
+  restoreMocks: true,
+  setupFilesAfterEnv: ['<rootDir>/src/__tests__/setup.ts']
+};