feat: Add build test and snapshot

This commit introduces a new build test for the project. It also
includes a snapshot for the expected output of the build process. The
build.ts file has been deleted as part of this change. A new fixture
file main.ts has been added to support the new test.

tests/__snapshots__/build.test.ts.snap

@@ -0,0 +1,7 @@
+// Bun Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`build 1`] = `
+"export type Str = string;
+export declare function hello(s: Str): Str;
+"
+`;

tests/build.test.ts

@@ -0,0 +1,20 @@
+import path from 'node:path';
+import { expect, test } from 'bun:test';
+import dts from '../index.ts';
+
+test('build', async () => {
+	const input = path.resolve(__dirname, 'fixtures/main.ts');
+	const dist = path.resolve(__dirname, 'out');
+
+	await Bun.build({
+		entrypoints: [input],
+		outdir: dist,
+		minify: false,
+		plugins: [dts()],
+		target: 'bun',
+		external: ['*'],
+	});
+
+	const outputDts = await Bun.file(path.resolve(dist, 'main.d.ts')).text();
+	expect(outputDts).toMatchSnapshot();
+});

tests/fixtures/main.ts

@@ -0,0 +1,5 @@
+export type Str = string;
+
+export function hello(s: Str): Str {
+	return `hello${s}`;
+}