test: native typescript loader

test/__snapshots__/built-in.test.ts.snap

@@ -0,0 +1,7 @@
+// Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
+
+exports[`built-in typescript 1`] = `
+{
+  "foo": "bar",
+}
+`;

test/built-in.test.ts

@@ -0,0 +1,14 @@
+import { resolve } from 'node:path'
+import { expect, it } from 'vitest'
+import { loadConfig } from '../src'
+
+const fixtureDir = resolve(__dirname, 'fixtures')
+
+it.skipIf(!process.features.typescript && !process.versions.bun)('built-in typescript', async () => {
+  const cwd = resolve(fixtureDir, 'builtin')
+  const result = await loadConfig({
+    sources: [{ files: 'un.config' }],
+    cwd,
+  })
+  expect(result.config).toMatchSnapshot()
+})

test/fixtures/builtin/un.config.ts

@@ -0,0 +1,5 @@
+let foo: string = 'bar'
+
+export default {
+  foo,
+}