test: add test case

test/index.js

@@ -1 +1,154 @@
-//
+import assert from 'node:assert';
+import test from 'node:test';
+import {
+	reduceConfigs,
+	reduceConfigsMergeContext,
+	reduceConfigsWithContext,
+} from '../dist/index.js';
+
+test('reduceConfigs should return initial config', () => {
+	assert.deepStrictEqual(reduceConfigs({ initial: { value: 'a' } }), {
+		value: 'a',
+	});
+});
+
+test('reduceConfigs should merge initial config', () => {
+	assert.deepStrictEqual(
+		reduceConfigs({
+			initial: { name: 'a' },
+			config: {
+				name: 'b',
+				custom: 'c',
+			},
+		}),
+		{
+			name: 'b',
+			custom: 'c',
+		},
+	);
+});
+
+test('reduceConfigs should support custom merge function', () => {
+	const merge = (target, source) => {
+		for (const key in source) {
+			if (Object.hasOwn(target, key)) {
+				target[key] += source[key];
+			} else {
+				target[key] = source[key];
+			}
+		}
+		return target;
+	};
+
+	assert.deepStrictEqual(
+		reduceConfigs({
+			initial: {
+				a: 1,
+				b: 'b',
+			},
+			config: {
+				a: 2,
+				b: 'b',
+				c: 'c',
+			},
+			mergeFn: merge,
+		}),
+		{
+			a: 3,
+			b: 'bb',
+			c: 'c',
+		},
+	);
+});
+
+test('reduceConfigs should support function or object array', () => {
+	const initial = { a: 'a' };
+
+	const config = [
+		{ b: 'b' },
+		(o, { add }) => {
+			o.c = add(1, 2);
+		},
+		(o) => ({
+			...o,
+			d: 'd',
+		}),
+		{ e: 'e' },
+	];
+
+	assert.deepStrictEqual(
+		reduceConfigsWithContext({
+			initial,
+			config,
+			ctx: {
+				add: (a, b) => a + b,
+			},
+		}),
+		{
+			a: 'a',
+			b: 'b',
+			c: 3,
+			d: 'd',
+			e: 'e',
+		},
+	);
+});
+
+test('reduceConfigs should support function and merge context', () => {
+	const initial = { a: 'a' };
+
+	const config = [
+		{ b: 'b' },
+		({ value, add }) => {
+			value.c = add(1, 2);
+		},
+		({ value }) => ({
+			...value,
+			d: 'd',
+		}),
+		{ e: 'e' },
+	];
+
+	assert.deepStrictEqual(
+		reduceConfigsMergeContext({
+			initial,
+			config,
+			ctx: {
+				add: (a, b) => a + b,
+			},
+		}),
+		{
+			a: 'a',
+			b: 'b',
+			c: 3,
+			d: 'd',
+			e: 'e',
+		},
+	);
+});
+
+test('reduceConfigs should allow false as config', () => {
+	assert.strictEqual(
+		reduceConfigs({
+			initial: 'head',
+			config: false,
+		}),
+		false,
+	);
+
+	assert.strictEqual(
+		reduceConfigs({
+			initial: 'head',
+			config: () => false,
+		}),
+		false,
+	);
+
+	assert.strictEqual(
+		reduceConfigs({
+			initial: 'head',
+			config: ['head', 'head', () => false],
+		}),
+		false,
+	);
+});