3 files changed, 48 insertions, 1 deletions
diff --git a/std/_util/assert.ts b/std/_util/assert.ts
new file mode 100644
index 000000000..d797591fe
--- /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 000000000..38aeae91b
--- /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 9034d89bd..ca1f0aba1 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>,