diff --git a/std/_util/assert.ts b/std/_util/assert.ts
new file mode 100644
index 0000000000..d797591fe0
--- /dev/null
+++ b/std/_util/assert.ts
@@ -0,0 +1,15 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+export class DenoStdInternalError extends Error {
+  constructor(message: string) {
+    super(message);
+    this.name = "DenoStdInternalError";
+  }
+}
+
+/** Make an assertion, if not `true`, then throw. */
+export function assert(expr: unknown, msg = ""): asserts expr {
+  if (!expr) {
+    throw new DenoStdInternalError(msg);
+  }
+}
diff --git a/std/_util/assert_test.ts b/std/_util/assert_test.ts
new file mode 100644
index 0000000000..38aeae91b3
--- /dev/null
+++ b/std/_util/assert_test.ts
@@ -0,0 +1,32 @@
+import { assert, DenoStdInternalError } from "./assert.ts";
+import { assertThrows } from "../testing/asserts.ts";
+
+const { test } = Deno;
+
+test({
+  name: "assert valid scenario",
+  fn(): void {
+    assert(true);
+  },
+});
+
+test({
+  name: "assert invalid scenario, no message",
+  fn(): void {
+    assertThrows(() => {
+      assert(false);
+    }, DenoStdInternalError);
+  },
+});
+test({
+  name: "assert invalid scenario, with message",
+  fn(): void {
+    assertThrows(
+      () => {
+        assert(false, "Oops! Should be true");
+      },
+      DenoStdInternalError,
+      "Oops! Should be true"
+    );
+  },
+});
diff --git a/std/_util/deep_assign.ts b/std/_util/deep_assign.ts
index 9034d89bdf..ca1f0aba11 100644
--- a/std/_util/deep_assign.ts
+++ b/std/_util/deep_assign.ts
@@ -1,5 +1,5 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
-import { assert } from "../testing/asserts.ts";
+import { assert } from "../_util/assert.ts";
 
 export function deepAssign(
   target: Record<string, unknown>,
diff --git a/std/archive/tar.ts b/std/archive/tar.ts
index 225bcb7693..52af7bd694 100644
--- a/std/archive/tar.ts
+++ b/std/archive/tar.ts
@@ -28,7 +28,7 @@
  */
 import { MultiReader } from "../io/readers.ts";
 import { BufReader } from "../io/bufio.ts";
-import { assert } from "../testing/asserts.ts";
+import { assert } from "../_util/assert.ts";
 
 const recordSize = 512;
 const ustar = "ustar\u000000";
diff --git a/std/datetime/mod.ts b/std/datetime/mod.ts
index 258388397d..7503eccb43 100644
--- a/std/datetime/mod.ts
+++ b/std/datetime/mod.ts
@@ -1,5 +1,5 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
-import { assert } from "../testing/asserts.ts";
+import { assert } from "../_util/assert.ts";
 
 export type DateFormat = "mm-dd-yyyy" | "dd-mm-yyyy" | "yyyy-mm-dd";
 
diff --git a/std/encoding/csv.ts b/std/encoding/csv.ts
index 3e7164cbb9..5af0545300 100644
--- a/std/encoding/csv.ts
+++ b/std/encoding/csv.ts
@@ -7,7 +7,7 @@
 import { BufReader } from "../io/bufio.ts";
 import { TextProtoReader } from "../textproto/mod.ts";
 import { StringReader } from "../io/readers.ts";
-import { assert } from "../testing/asserts.ts";
+import { assert } from "../_util/assert.ts";
 
 const INVALID_RUNE = ["\r", "\n", '"'];
 
diff --git a/std/encoding/toml.ts b/std/encoding/toml.ts
index 7e44bdc18d..8a0715ab68 100644
--- a/std/encoding/toml.ts
+++ b/std/encoding/toml.ts
@@ -1,6 +1,6 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 import { deepAssign } from "../_util/deep_assign.ts";
-import { assert } from "../testing/asserts.ts";
+import { assert } from "../_util/assert.ts";
 
 class KeyValuePair {
   constructor(public key: string, public value: unknown) {}
diff --git a/std/flags/mod.ts b/std/flags/mod.ts
index e3680087de..5c8fcc0d91 100644
--- a/std/flags/mod.ts
+++ b/std/flags/mod.ts
@@ -1,6 +1,6 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
-import { assert } from "../testing/asserts.ts";
+import { assert } from "../_util/assert.ts";
 
 export interface Args {
   /** Contains all the arguments that didn't have an option associated with
diff --git a/std/fs/copy.ts b/std/fs/copy.ts
index d45ac17c95..269340e850 100644
--- a/std/fs/copy.ts
+++ b/std/fs/copy.ts
@@ -2,7 +2,7 @@
 import * as path from "../path/mod.ts";
 import { ensureDir, ensureDirSync } from "./ensure_dir.ts";
 import { isSubdir, getFileInfoType } from "./_util.ts";
-import { assert } from "../testing/asserts.ts";
+import { assert } from "../_util/assert.ts";
 
 const isWindows = Deno.build.os === "windows";
 
diff --git a/std/fs/expand_glob.ts b/std/fs/expand_glob.ts
index e5abdabcf3..4b7b118854 100644
--- a/std/fs/expand_glob.ts
+++ b/std/fs/expand_glob.ts
@@ -14,7 +14,7 @@ import {
   walk,
   walkSync,
 } from "./walk.ts";
-import { assert } from "../testing/asserts.ts";
+import { assert } from "../_util/assert.ts";
 const { cwd } = Deno;
 type FileInfo = Deno.FileInfo;
 
diff --git a/std/fs/walk.ts b/std/fs/walk.ts
index ccd5097a49..553e52b2ec 100644
--- a/std/fs/walk.ts
+++ b/std/fs/walk.ts
@@ -1,7 +1,7 @@
 // Documentation and interface for walk were adapted from Go
 // https://golang.org/pkg/path/filepath/#Walk
 // Copyright 2009 The Go Authors. All rights reserved. BSD license.
-import { unimplemented, assert } from "../testing/asserts.ts";
+import { assert } from "../_util/assert.ts";
 import { basename, join, normalize } from "../path/mod.ts";
 const { readDir, readDirSync, stat, statSync } = Deno;
 
@@ -107,7 +107,7 @@ export async function* walk(
     if (entry.isSymlink) {
       if (followSymlinks) {
         // TODO(ry) Re-enable followSymlinks.
-        unimplemented();
+        throw new Error("unimplemented");
       } else {
         continue;
       }
@@ -159,7 +159,7 @@ export function* walkSync(
   for (const entry of readDirSync(root)) {
     if (entry.isSymlink) {
       if (followSymlinks) {
-        unimplemented();
+        throw new Error("unimplemented");
       } else {
         continue;
       }
diff --git a/std/http/_io.ts b/std/http/_io.ts
index 82954cceec..1db0fc2924 100644
--- a/std/http/_io.ts
+++ b/std/http/_io.ts
@@ -1,6 +1,6 @@
 import { BufReader, BufWriter } from "../io/bufio.ts";
 import { TextProtoReader } from "../textproto/mod.ts";
-import { assert } from "../testing/asserts.ts";
+import { assert } from "../_util/assert.ts";
 import { encoder } from "../encoding/utf8.ts";
 import { ServerRequest, Response } from "./server.ts";
 import { STATUS_TEXT } from "./http_status.ts";
diff --git a/std/http/cookie.ts b/std/http/cookie.ts
index a138eb3505..88a71626c9 100644
--- a/std/http/cookie.ts
+++ b/std/http/cookie.ts
@@ -2,7 +2,7 @@
 // Structured similarly to Go's cookie.go
 // https://github.com/golang/go/blob/master/src/net/http/cookie.go
 import { ServerRequest, Response } from "./server.ts";
-import { assert } from "../testing/asserts.ts";
+import { assert } from "../_util/assert.ts";
 import { toIMF } from "../datetime/mod.ts";
 
 export interface Cookies {
diff --git a/std/http/file_server.ts b/std/http/file_server.ts
index 7614c3ab2f..66babfd570 100755
--- a/std/http/file_server.ts
+++ b/std/http/file_server.ts
@@ -10,7 +10,7 @@ const { args, stat, readDir, open, exit } = Deno;
 import { posix, extname } from "../path/mod.ts";
 import { listenAndServe, ServerRequest, Response } from "./server.ts";
 import { parse } from "../flags/mod.ts";
-import { assert } from "../testing/asserts.ts";
+import { assert } from "../_util/assert.ts";
 
 interface EntryInfo {
   mode: string;
diff --git a/std/http/server.ts b/std/http/server.ts
index faf5da6af1..3cc95a9e49 100644
--- a/std/http/server.ts
+++ b/std/http/server.ts
@@ -1,7 +1,7 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 import { encode } from "../encoding/utf8.ts";
 import { BufReader, BufWriter } from "../io/bufio.ts";
-import { assert } from "../testing/asserts.ts";
+import { assert } from "../_util/assert.ts";
 import { deferred, Deferred, MuxAsyncIterator } from "../async/mod.ts";
 import {
   bodyReader,
diff --git a/std/io/bufio.ts b/std/io/bufio.ts
index 5c005672a3..4ebec13e1d 100644
--- a/std/io/bufio.ts
+++ b/std/io/bufio.ts
@@ -7,7 +7,7 @@ type Reader = Deno.Reader;
 type Writer = Deno.Writer;
 type WriterSync = Deno.WriterSync;
 import { charCode, copyBytes } from "./util.ts";
-import { assert } from "../testing/asserts.ts";
+import { assert } from "../_util/assert.ts";
 
 const DEFAULT_BUF_SIZE = 4096;
 const MIN_BUF_SIZE = 16;
diff --git a/std/io/ioutil.ts b/std/io/ioutil.ts
index aff9f05e2c..3d9e72b569 100644
--- a/std/io/ioutil.ts
+++ b/std/io/ioutil.ts
@@ -2,7 +2,7 @@
 import { BufReader } from "./bufio.ts";
 type Reader = Deno.Reader;
 type Writer = Deno.Writer;
-import { assert } from "../testing/asserts.ts";
+import { assert } from "../_util/assert.ts";
 
 const DEFAULT_BUFFER_SIZE = 32 * 1024;
 
diff --git a/std/log/mod.ts b/std/log/mod.ts
index 983e824015..e596c81ba8 100644
--- a/std/log/mod.ts
+++ b/std/log/mod.ts
@@ -7,7 +7,7 @@ import {
   FileHandler,
   RotatingFileHandler,
 } from "./handlers.ts";
-import { assert } from "../testing/asserts.ts";
+import { assert } from "../_util/assert.ts";
 import { LevelName } from "./levels.ts";
 
 export { LogLevels } from "./levels.ts";
diff --git a/std/mime/multipart.ts b/std/mime/multipart.ts
index 5d9ee7cf9c..73a6544b5b 100644
--- a/std/mime/multipart.ts
+++ b/std/mime/multipart.ts
@@ -12,7 +12,7 @@ import { extname } from "../path/mod.ts";
 import { tempFile } from "../io/util.ts";
 import { BufReader, BufWriter } from "../io/bufio.ts";
 import { encoder } from "../encoding/utf8.ts";
-import { assertStrictEquals, assert } from "../testing/asserts.ts";
+import { assert } from "../_util/assert.ts";
 import { TextProtoReader } from "../textproto/mod.ts";
 import { hasOwnProperty } from "../_util/has_own_property.ts";
 
@@ -178,7 +178,7 @@ class PartReader implements Reader, Closer {
       );
       if (this.n === 0) {
         // Force buffered I/O to read more into buffer.
-        assertStrictEquals(eof, false);
+        assert(eof === false);
         peekLength++;
       }
     }
@@ -190,7 +190,7 @@ class PartReader implements Reader, Closer {
     const nread = min(p.length, this.n);
     const buf = p.subarray(0, nread);
     const r = await br.readFull(buf);
-    assertStrictEquals(r, buf);
+    assert(r === buf);
     this.n -= nread;
     this.total += nread;
     return nread;
diff --git a/std/node/_fs/_fs_dir.ts b/std/node/_fs/_fs_dir.ts
index a39422ce06..7f2085b3b1 100644
--- a/std/node/_fs/_fs_dir.ts
+++ b/std/node/_fs/_fs_dir.ts
@@ -1,5 +1,5 @@
 import Dirent from "./_fs_dirent.ts";
-import { assert } from "../../testing/asserts.ts";
+import { assert } from "../../_util/assert.ts";
 
 export default class Dir {
   private dirPath: string | Uint8Array;
diff --git a/std/node/events.ts b/std/node/events.ts
index aa62e4d432..cb9acb0f5a 100644
--- a/std/node/events.ts
+++ b/std/node/events.ts
@@ -22,7 +22,7 @@
 // USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 import { validateIntegerRange } from "./util.ts";
-import { assert } from "../testing/asserts.ts";
+import { assert } from "../_util/assert.ts";
 
 export interface WrappedFunction extends Function {
   listener: Function;
diff --git a/std/node/module.ts b/std/node/module.ts
index 8d0160f78a..daa01d2b24 100644
--- a/std/node/module.ts
+++ b/std/node/module.ts
@@ -31,7 +31,7 @@ import * as nodeEvents from "./events.ts";
 import * as nodeQueryString from "./querystring.ts";
 
 import * as path from "../path/mod.ts";
-import { assert } from "../testing/asserts.ts";
+import { assert } from "../_util/assert.ts";
 import { pathToFileURL, fileURLToPath } from "./url.ts";
 
 const CHAR_FORWARD_SLASH = "/".charCodeAt(0);
diff --git a/std/path/glob.ts b/std/path/glob.ts
index 34fc213f62..c7d23b3441 100644
--- a/std/path/glob.ts
+++ b/std/path/glob.ts
@@ -4,7 +4,7 @@
 import { SEP, SEP_PATTERN } from "./separator.ts";
 import { globrex } from "./_globrex.ts";
 import { join, normalize } from "./mod.ts";
-import { assert } from "../testing/asserts.ts";
+import { assert } from "../_util/assert.ts";
 
 export interface GlobOptions {
   extended?: boolean;
diff --git a/std/path/win32.ts b/std/path/win32.ts
index f556c5b736..8e438a79c3 100644
--- a/std/path/win32.ts
+++ b/std/path/win32.ts
@@ -17,7 +17,7 @@ import {
   normalizeString,
   _format,
 } from "./_util.ts";
-import { assert } from "../testing/asserts.ts";
+import { assert } from "../_util/assert.ts";
 
 export const sep = "\\";
 export const delimiter = ";";
diff --git a/std/uuid/v5.ts b/std/uuid/v5.ts
index 3c04873fec..f982d9745a 100644
--- a/std/uuid/v5.ts
+++ b/std/uuid/v5.ts
@@ -8,7 +8,7 @@ import {
 } from "./_common.ts";
 import { Sha1 } from "../hash/sha1.ts";
 import { isString } from "../node/util.ts";
-import { assert } from "../testing/asserts.ts";
+import { assert } from "../_util/assert.ts";
 
 const UUID_RE = /^[0-9a-f]{8}-[0-9a-f]{4}-[5][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i;
 
diff --git a/std/ws/mod.ts b/std/ws/mod.ts
index f98e70d928..f58828aea8 100644
--- a/std/ws/mod.ts
+++ b/std/ws/mod.ts
@@ -8,7 +8,7 @@ import { Sha1 } from "../hash/sha1.ts";
 import { writeResponse } from "../http/_io.ts";
 import { TextProtoReader } from "../textproto/mod.ts";
 import { Deferred, deferred } from "../async/deferred.ts";
-import { assert } from "../testing/asserts.ts";
+import { assert } from "../_util/assert.ts";
 import { concat } from "../bytes/mod.ts";
 import Conn = Deno.Conn;
 import Writer = Deno.Writer;