diff --git a/http/io_test.ts b/http/io_test.ts
index b9bb56f1196d5..fd41b474e391f 100644
--- a/http/io_test.ts
+++ b/http/io_test.ts
@@ -51,7 +51,7 @@ test("chunkedBodyReader", async () => {
     await dest.write(buf.subarray(0, len));
   }
   const exp = "aaabbbbbcccccccccccdddddddddddddddddddddd";
-  assertEquals(dest.toString(), exp);
+  assertEquals(new TextDecoder().decode(dest.bytes()), exp);
 });
 
 test("chunkedBodyReader with trailers", async () => {
@@ -133,7 +133,10 @@ test("writeTrailer", async () => {
     new Headers({ "transfer-encoding": "chunked", trailer: "deno,node" }),
     new Headers({ deno: "land", node: "js" })
   );
-  assertEquals(w.toString(), "deno: land\r\nnode: js\r\n\r\n");
+  assertEquals(
+    new TextDecoder().decode(w.bytes()),
+    "deno: land\r\nnode: js\r\n\r\n"
+  );
 });
 
 test("writeTrailer should throw", async () => {
@@ -336,7 +339,7 @@ test("writeResponse with trailer", async () => {
     body,
     trailers: () => new Headers({ deno: "land", node: "js" }),
   });
-  const ret = w.toString();
+  const ret = new TextDecoder().decode(w.bytes());
   const exp = [
     "HTTP/1.1 200 OK",
     "transfer-encoding: chunked",
diff --git a/http/server_test.ts b/http/server_test.ts
index 4e7b4b69e588a..03256dd25ca64 100644
--- a/http/server_test.ts
+++ b/http/server_test.ts
@@ -63,7 +63,7 @@ test("responseWrite", async function (): Promise<void> {
     request.conn = mockConn();
 
     await request.respond(testCase.response);
-    assertEquals(buf.toString(), testCase.raw);
+    assertEquals(new TextDecoder().decode(buf.bytes()), testCase.raw);
     await request.done;
   }
 });
diff --git a/io/ioutil_test.ts b/io/ioutil_test.ts
index 1f552d0e6d2d3..cf8eaf43739b4 100644
--- a/io/ioutil_test.ts
+++ b/io/ioutil_test.ts
@@ -76,7 +76,7 @@ Deno.test("testCopyN1", async function (): Promise<void> {
   const r = stringsReader("abcdefghij");
   const n = await copyN(r, w, 3);
   assertEquals(n, 3);
-  assertEquals(w.toString(), "abc");
+  assertEquals(new TextDecoder().decode(w.bytes()), "abc");
 });
 
 Deno.test("testCopyN2", async function (): Promise<void> {
@@ -84,7 +84,7 @@ Deno.test("testCopyN2", async function (): Promise<void> {
   const r = stringsReader("abcdefghij");
   const n = await copyN(r, w, 11);
   assertEquals(n, 10);
-  assertEquals(w.toString(), "abcdefghij");
+  assertEquals(new TextDecoder().decode(w.bytes()), "abcdefghij");
 });
 
 Deno.test("copyNWriteAllData", async function (): Promise<void> {
diff --git a/mime/multipart.ts b/mime/multipart.ts
index 48e32c65d8c26..b2ac8dcdd3afb 100644
--- a/mime/multipart.ts
+++ b/mime/multipart.ts
@@ -302,7 +302,7 @@ export class MultipartReader {
         if (maxValueBytes < 0) {
           throw new RangeError("message too large");
         }
-        const value = buf.toString();
+        const value = new TextDecoder().decode(buf.bytes());
         valueMap.set(p.formName, value);
         continue;
       }
diff --git a/ws/test.ts b/ws/test.ts
index c6e74dadcb5c5..796bf3bb81ac0 100644
--- a/ws/test.ts
+++ b/ws/test.ts
@@ -31,7 +31,8 @@ test("[ws] read unmasked text frame", async () => {
   const frame = await readFrame(buf);
   assertEquals(frame.opcode, OpCode.TextFrame);
   assertEquals(frame.mask, undefined);
-  assertEquals(new Buffer(frame.payload).toString(), "Hello");
+  const actual = new TextDecoder().decode(new Buffer(frame.payload).bytes());
+  assertEquals(actual, "Hello");
   assertEquals(frame.isLastFrame, true);
 });
 
@@ -57,7 +58,8 @@ test("[ws] read masked text frame", async () => {
   const frame = await readFrame(buf);
   assertEquals(frame.opcode, OpCode.TextFrame);
   unmask(frame.payload, frame.mask);
-  assertEquals(new Buffer(frame.payload).toString(), "Hello");
+  const actual = new TextDecoder().decode(new Buffer(frame.payload).bytes());
+  assertEquals(actual, "Hello");
   assertEquals(frame.isLastFrame, true);
 });
 
@@ -72,12 +74,14 @@ test("[ws] read unmasked split text frames", async () => {
   assertEquals(f1.isLastFrame, false);
   assertEquals(f1.mask, undefined);
   assertEquals(f1.opcode, OpCode.TextFrame);
-  assertEquals(new Buffer(f1.payload).toString(), "Hel");
+  const actual1 = new TextDecoder().decode(new Buffer(f1.payload).bytes());
+  assertEquals(actual1, "Hel");
 
   assertEquals(f2.isLastFrame, true);
   assertEquals(f2.mask, undefined);
   assertEquals(f2.opcode, OpCode.Continue);
-  assertEquals(new Buffer(f2.payload).toString(), "lo");
+  const actual2 = new TextDecoder().decode(new Buffer(f2.payload).bytes());
+  assertEquals(actual2, "lo");
 });
 
 test("[ws] read unmasked ping / pong frame", async () => {
@@ -87,7 +91,8 @@ test("[ws] read unmasked ping / pong frame", async () => {
   );
   const ping = await readFrame(buf);
   assertEquals(ping.opcode, OpCode.Ping);
-  assertEquals(new Buffer(ping.payload).toString(), "Hello");
+  const actual1 = new TextDecoder().decode(new Buffer(ping.payload).bytes());
+  assertEquals(actual1, "Hello");
   // prettier-ignore
   const pongFrame= [0x8a, 0x85, 0x37, 0xfa, 0x21, 0x3d, 0x7f, 0x9f, 0x4d, 0x51, 0x58]
   const buf2 = new BufReader(new Buffer(new Uint8Array(pongFrame)));
@@ -95,7 +100,8 @@ test("[ws] read unmasked ping / pong frame", async () => {
   assertEquals(pong.opcode, OpCode.Pong);
   assert(pong.mask !== undefined);
   unmask(pong.payload, pong.mask);
-  assertEquals(new Buffer(pong.payload).toString(), "Hello");
+  const actual2 = new TextDecoder().decode(new Buffer(pong.payload).bytes());
+  assertEquals(actual2, "Hello");
 });
 
 test("[ws] read unmasked big binary frame", async () => {