add basic server tests (#51)

src/client/tests/basic.test.ts

···
 	t.assert.strictEqual(el.innerHTML, '<!---->')
 })
 
-test('invalid part placement produces warning', { skip: process.env.NODE_ENV === 'production' }, (t: TestContext) => {
+test('invalid part placement raises error', { skip: process.env.NODE_ENV === 'production' }, (t: TestContext) => {
 	const { root, el } = setup()
 
 	t.assert.throws(() => root.render(html`<${'div'}>${'text'}</${'div'}>`), {

src/server.ts

···
 	const { _statics: statics, _dynamics: dynamics } = is_html(value) ? value : single_part_template(value)
 	const template = compile_template(statics)
 
+	assert(
+		template.parts.length === dynamics.length,
+		'expected the same number of dynamics as parts. do you have a ${...} in an unsupported place?',
+	)
+
 	for (let i = 0; i < template.statics.length - 1; i++) {
 		yield template.statics[i]
 		yield* template.parts[i](dynamics)

src/server/tests/basic.test.ts

···
+import { html } from 'dhtml'
+import { renderToString } from 'dhtml/server'
+import test, { type TestContext } from 'node:test'
+
+globalThis.__DEV__ = process.env.NODE_ENV !== 'production'
+
+test('basic html renders correctly', (t: TestContext) => {
+	t.assert.strictEqual(renderToString(html`<h1>Hello, world!</h1>`), '<h1>Hello, world!</h1>')
+})
+
+test('inner content renders correctly', (t: TestContext) => {
+	t.assert.strictEqual(renderToString(html`<h1>${html`Inner content!`}</h1>`), '<h1>Inner content!</h1>')
+})
+
+test('template with number renders correctly', (t: TestContext) => {
+	const template = (n: number) => html`<h1>Hello, ${n}!</h1>`
+	t.assert.strictEqual(renderToString(template(1)), '<h1>Hello, 1!</h1>')
+	t.assert.strictEqual(renderToString(template(2)), '<h1>Hello, 2!</h1>')
+})
+
+test('basic children render correctly', (t: TestContext) => {
+	t.assert.strictEqual(
+		renderToString(html`<span>${'This is a'}</span> ${html`test`} ${html`test`} ${html`test`}`),
+		'<span>This is a</span> test test test',
+	)
+})
+
+test('errors are thrown cleanly', (t: TestContext) => {
+	const oops = new Error('oops')
+	let thrown
+	try {
+		renderToString(
+			html`${{
+				render() {
+					throw oops
+				},
+			}}`,
+		)
+	} catch (error) {
+		thrown = error
+	}
+	t.assert.strictEqual(thrown, oops)
+})
+
+test('invalid part placement raises error', { skip: process.env.NODE_ENV === 'production' }, (t: TestContext) => {
+	t.assert.throws(() => renderToString(html`<${'div'}>${'text'}</${'div'}>`))
+})
+
+test('parts in comments do not throw', (t: TestContext) => {
+	renderToString(html`<!-- ${'text'} -->`)
+})
+
+test(
+	'manually specifying internal template syntax throws',
+	{ skip: process.env.NODE_ENV === 'production' },
+	(t: TestContext) => {
+		t.assert.throws(() => {
+			renderToString(html`${1} dyn-$0$`)
+		})
+	},
+)
+
+test('syntax close but not exact does not throw', (t: TestContext) => {
+	t.assert.strictEqual(renderToString(html`dyn-$${0}1$`), 'dyn-$01$')
+})