diff --git a/macho/universal.test.ts b/macho/universal.test.ts
index 8b37b60..127b6db 100644
--- a/macho/universal.test.ts
+++ b/macho/universal.test.ts
@@ -5,7 +5,10 @@ import {
 	assertLessOrEqual,
 	assertThrows,
 } from '@std/assert';
-import { MH_DYLIB, MH_EXECUTE } from '../const.ts';
+import { FAT_MAGIC, MH_DYLIB, MH_EXECUTE } from '../const.ts';
+import { FatArch } from '../mach/fatarch.ts';
+import { FatHeader } from '../mach/fatheader.ts';
+import { MachHeader } from '../mach/machheader.ts';
 import { fixtureMacho, fixtureMachos } from '../spec/fixture.ts';
 import { Architecture } from './architecture.ts';
 import { Universal } from './universal.ts';
@@ -74,3 +77,33 @@ for (const { kind, arch, file, archs } of fixtures) {
 		}
 	});
 }
+
+Deno.test('typeOf under header', async () => {
+	const blob = new Blob([new ArrayBuffer(MachHeader.BYTE_LENGTH - 1)]);
+	assertEquals(await Universal.typeOf(blob), 0);
+});
+
+Deno.test('typeOf unknown magic', async () => {
+	const blob = new Blob([new ArrayBuffer(MachHeader.BYTE_LENGTH)]);
+	assertEquals(await Universal.typeOf(blob), 0);
+});
+
+Deno.test('typeOf fat arch under', async () => {
+	const data = new ArrayBuffer(FatHeader.BYTE_LENGTH + FatArch.BYTE_LENGTH);
+	const header = new FatHeader(data);
+	header.magic = FAT_MAGIC;
+	header.nfatArch = 1;
+	const arch = new FatArch(data, FatHeader.BYTE_LENGTH);
+	arch.offset = data.byteLength;
+	const blob = new Blob([data]);
+	assertEquals(await Universal.typeOf(blob), 0);
+});
+
+Deno.test('typeOf fat infinite loop', async () => {
+	const data = new ArrayBuffer(FatHeader.BYTE_LENGTH + FatArch.BYTE_LENGTH);
+	const header = new FatHeader(data);
+	header.magic = FAT_MAGIC;
+	header.nfatArch = 1;
+	const blob = new Blob([data]);
+	assertEquals(await Universal.typeOf(blob), 0);
+});