Add type testing

Author: fregante

.github/workflows/ci.yml

@@ -32,4 +32,4 @@ jobs:
       - name: build
         run: npm run build --if-present
       - name: Vitest
-        run: npx vitest
+        run: npx vitest --typecheck

index.test-d.ts

@@ -0,0 +1,46 @@
+import {expectTypeOf, it} from 'vitest';
+import ManyKeysMap from './index.js';
+
+it('should be a class that extends Map', () => {
+	// Use toBeConstructibleWith() for checking if a class is constructible
+	expectTypeOf(ManyKeysMap).toBeConstructibleWith();
+	expectTypeOf(ManyKeysMap.prototype).toMatchTypeOf(Map.prototype);
+});
+
+it('should correctly infer key and value types', () => {
+  type KeyTuple = [string, number];
+  type ValueType = {id: string; name: string};
+
+  const map = new ManyKeysMap<KeyTuple, ValueType>();
+
+  // Use toEqualTypeOf() for checking the type of an instance
+  expectTypeOf(map).toEqualTypeOf<ManyKeysMap<KeyTuple, ValueType>>();
+  expectTypeOf(map).not.toEqualTypeOf<ManyKeysMap<[number], string>>();
+
+  // Test set method
+  expectTypeOf(map.set).parameter(0).toEqualTypeOf<KeyTuple>();
+  expectTypeOf(map.set).parameter(1).toEqualTypeOf<ValueType>();
+  expectTypeOf(map.set(['a', 1], {id: 'x', name: 'y'})).toEqualTypeOf<typeof map>();
+
+  // Test get method
+  expectTypeOf(map.get).parameter(0).toEqualTypeOf<KeyTuple>();
+  expectTypeOf(map.get(['a', 1])).toEqualTypeOf<ValueType | undefined>();
+
+  // Test has method
+  expectTypeOf(map.has).parameter(0).toEqualTypeOf<KeyTuple>();
+  expectTypeOf(map.has(['a', 1])).toEqualTypeOf<boolean>();
+
+  // Test delete method
+  expectTypeOf(map.delete).parameter(0).toEqualTypeOf<KeyTuple>();
+  expectTypeOf(map.delete(['a', 1])).toEqualTypeOf<boolean>();
+});
+
+it('should handle different key and value types', () => {
+  type DiverseKey = [boolean, number, string];
+  type DiverseValue = {status: 'active' | 'inactive'};
+
+  const map = new ManyKeysMap<DiverseKey, DiverseValue>();
+
+  expectTypeOf(map.set([true, 123, 'hello'], {status: 'active'})).toEqualTypeOf<typeof map>();
+  expectTypeOf(map.get([false, 456, 'world'])).toEqualTypeOf<DiverseValue | undefined>();
+});

package.json

@@ -24,7 +24,7 @@
 		"index.js"
 	],
 	"scripts": {
-		"test": "tsc && xo && vitest"
+		"test": "tsc && xo && vitest --typecheck"
 	},
 	"xo": {
 		"rules": {