diff --git a/cli/tests/unit/truncate_test.ts b/cli/tests/unit/truncate_test.ts
index b9e3a341c9..0148157026 100644
--- a/cli/tests/unit/truncate_test.ts
+++ b/cli/tests/unit/truncate_test.ts
@@ -1,36 +1,17 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 import { unitTest, assertEquals, assert } from "./test_util.ts";
 
-function readDataSync(name: string): string {
-  const data = Deno.readFileSync(name);
-  const decoder = new TextDecoder("utf-8");
-  const text = decoder.decode(data);
-  return text;
-}
-
-async function readData(name: string): Promise<string> {
-  const data = await Deno.readFile(name);
-  const decoder = new TextDecoder("utf-8");
-  const text = decoder.decode(data);
-  return text;
-}
-
 unitTest(
   { perms: { read: true, write: true } },
   function truncateSyncSuccess(): void {
-    const enc = new TextEncoder();
-    const d = enc.encode("Hello");
     const filename = Deno.makeTempDirSync() + "/test_truncateSync.txt";
-    Deno.writeFileSync(filename, d);
+    Deno.writeFileSync(filename, new Uint8Array(5));
     Deno.truncateSync(filename, 20);
-    let data = readDataSync(filename);
-    assertEquals(data.length, 20);
+    assertEquals(Deno.readFileSync(filename).byteLength, 20);
     Deno.truncateSync(filename, 5);
-    data = readDataSync(filename);
-    assertEquals(data.length, 5);
+    assertEquals(Deno.readFileSync(filename).byteLength, 5);
     Deno.truncateSync(filename, -5);
-    data = readDataSync(filename);
-    assertEquals(data.length, 0);
+    assertEquals(Deno.readFileSync(filename).byteLength, 0);
     Deno.removeSync(filename);
   }
 );
@@ -38,19 +19,14 @@ unitTest(
 unitTest(
   { perms: { read: true, write: true } },
   async function truncateSuccess(): Promise<void> {
-    const enc = new TextEncoder();
-    const d = enc.encode("Hello");
     const filename = Deno.makeTempDirSync() + "/test_truncate.txt";
-    await Deno.writeFile(filename, d);
+    await Deno.writeFile(filename, new Uint8Array(5));
     await Deno.truncate(filename, 20);
-    let data = await readData(filename);
-    assertEquals(data.length, 20);
+    assertEquals((await Deno.readFile(filename)).byteLength, 20);
     await Deno.truncate(filename, 5);
-    data = await readData(filename);
-    assertEquals(data.length, 5);
+    assertEquals((await Deno.readFile(filename)).byteLength, 5);
     await Deno.truncate(filename, -5);
-    data = await readData(filename);
-    assertEquals(data.length, 0);
+    assertEquals((await Deno.readFile(filename)).byteLength, 0);
     await Deno.remove(filename);
   }
 );