Add mdx?no-dts testing

test/mdx/mdx.test.ts

@@ -0,0 +1,28 @@
+import { assertStringIncludes } from "https://deno.land/std@0.155.0/testing/asserts.ts";
+
+import { compile } from "http://localhost:8080/@mdx-js/mdx@2.1.3?no-dts";
+
+const md = `
+export const Thing = () => <>World!</>
+
+# Hello, <Thing />
+
+\`\`\`js
+console.log("Hello, World!")
+\`\`\`
+`;
+
+Deno.test("mdx?no-dts", async () => {
+  const output = await compile(md, {
+    jsxImportSource: "https://esm.sh/react@18.2.0",
+  });
+  const code = output.toString();
+  assertStringIncludes(
+    code,
+    `import {Fragment as _Fragment, jsx as _jsx, jsxs as _jsxs} from "https://esm.sh/react@18.2.0/jsx-runtime";`,
+  );
+  assertStringIncludes(code, `"h1"`);
+  assertStringIncludes(code, `"code"`);
+  assertStringIncludes(code, `"pre"`);
+  assertStringIncludes(code, `className: "language-js"`);
+});