diff --git a/examples/xeval_test.ts b/examples/xeval_test.ts
index 972d71ae4bf6..6d24d08bb4e6 100644
--- a/examples/xeval_test.ts
+++ b/examples/xeval_test.ts
@@ -5,7 +5,7 @@ import { decode, encode } from "../encoding/utf8.ts";
 import {
   assert,
   assertEquals,
-  assertStringContains,
+  assertStringIncludes,
 } from "../testing/asserts.ts";
 import { dirname, fromFileUrl } from "../path/mod.ts";
 
@@ -66,6 +66,6 @@ Deno.test("xevalCliSyntaxError", async function (): Promise<void> {
   });
   assertEquals(await p.status(), { code: 1, success: false });
   assertEquals(decode(await p.output()), "");
-  assertStringContains(decode(await p.stderrOutput()), "SyntaxError");
+  assertStringIncludes(decode(await p.stderrOutput()), "SyntaxError");
   p.close();
 });
diff --git a/fs/empty_dir_test.ts b/fs/empty_dir_test.ts
index 851fe37b969f..6c34061158b0 100644
--- a/fs/empty_dir_test.ts
+++ b/fs/empty_dir_test.ts
@@ -2,7 +2,7 @@
 import {
   assert,
   assertEquals,
-  assertStringContains,
+  assertStringIncludes,
   assertThrows,
   assertThrowsAsync,
 } from "../testing/asserts.ts";
@@ -231,7 +231,7 @@ for (const s of scenes) {
         assert(p.stdout);
         const output = await p.output();
         p.close();
-        assertStringContains(new TextDecoder().decode(output), s.output);
+        assertStringIncludes(new TextDecoder().decode(output), s.output);
       } catch (err) {
         await Deno.remove(testfolder, { recursive: true });
         throw err;
diff --git a/fs/exists_test.ts b/fs/exists_test.ts
index f4088e03a35e..6619cce10462 100644
--- a/fs/exists_test.ts
+++ b/fs/exists_test.ts
@@ -1,5 +1,5 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
-import { assertEquals, assertStringContains } from "../testing/asserts.ts";
+import { assertEquals, assertStringIncludes } from "../testing/asserts.ts";
 import * as path from "../path/mod.ts";
 import { exists, existsSync } from "./exists.ts";
 
@@ -130,7 +130,7 @@ for (const s of scenes) {
 
     const output = await p.output();
     p.close();
-    assertStringContains(new TextDecoder().decode(output), s.output);
+    assertStringIncludes(new TextDecoder().decode(output), s.output);
   });
   // done
 }
diff --git a/fs/expand_glob_test.ts b/fs/expand_glob_test.ts
index 39235906b6c7..768c6465aeb9 100644
--- a/fs/expand_glob_test.ts
+++ b/fs/expand_glob_test.ts
@@ -3,7 +3,7 @@ import { decode } from "../encoding/utf8.ts";
 import {
   assert,
   assertEquals,
-  assertStringContains,
+  assertStringIncludes,
 } from "../testing/asserts.ts";
 import {
   fromFileUrl,
@@ -126,7 +126,7 @@ Deno.test("expandGlobPermError", async function (): Promise<void> {
   });
   assertEquals(await p.status(), { code: 1, success: false });
   assertEquals(decode(await p.output()), "");
-  assertStringContains(
+  assertStringIncludes(
     decode(await p.stderrOutput()),
     "Uncaught PermissionDenied",
   );
diff --git a/http/server_test.ts b/http/server_test.ts
index 76b0bcff9176..f26dc63cd2be 100644
--- a/http/server_test.ts
+++ b/http/server_test.ts
@@ -10,7 +10,7 @@ import {
   assert,
   assertEquals,
   assertMatch,
-  assertStringContains,
+  assertStringIncludes,
   assertThrowsAsync,
 } from "../testing/asserts.ts";
 import {
@@ -498,7 +498,7 @@ Deno.test({
     const nread = await conn.read(res);
     assert(nread !== null);
     const resStr = new TextDecoder().decode(res.subarray(0, nread));
-    assertStringContains(resStr, "/hello");
+    assertStringIncludes(resStr, "/hello");
     server.close();
     await p;
     // Client connection should still be open, verify that
diff --git a/node/module_test.ts b/node/module_test.ts
index 2b8c5c790529..2b3ed3eedf0c 100644
--- a/node/module_test.ts
+++ b/node/module_test.ts
@@ -3,7 +3,7 @@
 import {
   assert,
   assertEquals,
-  assertStringContains,
+  assertStringIncludes,
 } from "../testing/asserts.ts";
 
 import * as path from "../path/mod.ts";
@@ -67,6 +67,6 @@ Deno.test("requireStack", function () {
   try {
     hello();
   } catch (e) {
-    assertStringContains(e.stack, "/tests/cjs/cjs_throw.js");
+    assertStringIncludes(e.stack, "/tests/cjs/cjs_throw.js");
   }
 });
diff --git a/testing/README.md b/testing/README.md
index f970471cbc97..2cff96a6d6a3 100644
--- a/testing/README.md
+++ b/testing/README.md
@@ -18,12 +18,12 @@ pretty-printed diff of failing assertion.
   and `expected` are equal.
 - `assertStrictEquals()` - Compares `actual` and `expected` strictly, therefore
   for non-primitives the values must reference the same instance.
-- `assertStringContains()` - Make an assertion that `actual` contains
+- `assertStringIncludes()` - Make an assertion that `actual` includes
   `expected`.
 - `assertMatch()` - Make an assertion that `actual` match RegExp `expected`.
 - `assertNotMatch()` - Make an assertion that `actual` not match RegExp
   `expected`.
-- `assertArrayContains()` - Make an assertion that `actual` array contains the
+- `assertArrayIncludes()` - Make an assertion that `actual` array includes the
   `expected` values.
 - `assertObjectMatch()` - Make an assertion that `actual` object match
   `expected` subset object
diff --git a/testing/asserts.ts b/testing/asserts.ts
index 1d58f0a001e4..d46b26dedbf3 100644
--- a/testing/asserts.ts
+++ b/testing/asserts.ts
@@ -330,10 +330,10 @@ export function assertNotStrictEquals(
 }
 
 /**
- * Make an assertion that actual contains expected. If not
+ * Make an assertion that actual includes expected. If not
  * then thrown.
  */
-export function assertStringContains(
+export function assertStringIncludes(
   actual: string,
   expected: string,
   msg?: string,
@@ -347,26 +347,26 @@ export function assertStringContains(
 }
 
 /**
- * Make an assertion that `actual` contains the `expected` values.
+ * Make an assertion that `actual` includes the `expected` values.
  * If not then an error will be thrown.
  *
  * Type parameter can be specified to ensure values under comparison have the same type.
  * For example:
  *```ts
- *assertArrayContains<number>([1, 2], [2])
+ *assertArrayIncludes<number>([1, 2], [2])
  *```
  */
-export function assertArrayContains(
+export function assertArrayIncludes(
   actual: ArrayLike<unknown>,
   expected: ArrayLike<unknown>,
   msg?: string,
 ): void;
-export function assertArrayContains<T>(
+export function assertArrayIncludes<T>(
   actual: ArrayLike<T>,
   expected: ArrayLike<T>,
   msg?: string,
 ): void;
-export function assertArrayContains(
+export function assertArrayIncludes(
   actual: ArrayLike<unknown>,
   expected: ArrayLike<unknown>,
   msg?: string,
@@ -388,7 +388,7 @@ export function assertArrayContains(
     return;
   }
   if (!msg) {
-    msg = `actual: "${_format(actual)}" expected to contain: "${
+    msg = `actual: "${_format(actual)}" expected to include: "${
       _format(expected)
     }"\nmissing: ${_format(missing)}`;
   }
diff --git a/testing/asserts_test.ts b/testing/asserts_test.ts
index a0db48e7bacb..d357a761beb3 100644
--- a/testing/asserts_test.ts
+++ b/testing/asserts_test.ts
@@ -2,7 +2,7 @@
 import {
   _format,
   assert,
-  assertArrayContains,
+  assertArrayIncludes,
   assertEquals,
   AssertionError,
   assertMatch,
@@ -11,7 +11,7 @@ import {
   assertNotStrictEquals,
   assertObjectMatch,
   assertStrictEquals,
-  assertStringContains,
+  assertStringIncludes,
   assertThrows,
   assertThrowsAsync,
   equal,
@@ -161,12 +161,12 @@ Deno.test("testingNotEquals", function (): void {
 });
 
 Deno.test("testingAssertStringContains", function (): void {
-  assertStringContains("Denosaurus", "saur");
-  assertStringContains("Denosaurus", "Deno");
-  assertStringContains("Denosaurus", "rus");
+  assertStringIncludes("Denosaurus", "saur");
+  assertStringIncludes("Denosaurus", "Deno");
+  assertStringIncludes("Denosaurus", "rus");
   let didThrow;
   try {
-    assertStringContains("Denosaurus", "Raptor");
+    assertStringIncludes("Denosaurus", "Raptor");
     didThrow = false;
   } catch (e) {
     assert(e instanceof AssertionError);
@@ -178,14 +178,14 @@ Deno.test("testingAssertStringContains", function (): void {
 Deno.test("testingArrayContains", function (): void {
   const fixture = ["deno", "iz", "luv"];
   const fixtureObject = [{ deno: "luv" }, { deno: "Js" }];
-  assertArrayContains(fixture, ["deno"]);
-  assertArrayContains(fixtureObject, [{ deno: "luv" }]);
-  assertArrayContains(
+  assertArrayIncludes(fixture, ["deno"]);
+  assertArrayIncludes(fixtureObject, [{ deno: "luv" }]);
+  assertArrayIncludes(
     Uint8Array.from([1, 2, 3, 4]),
     Uint8Array.from([1, 2, 3]),
   );
   assertThrows(
-    (): void => assertArrayContains(fixtureObject, [{ deno: "node" }]),
+    (): void => assertArrayIncludes(fixtureObject, [{ deno: "node" }]),
     AssertionError,
     `actual: "[
   {
@@ -194,7 +194,7 @@ Deno.test("testingArrayContains", function (): void {
   {
     deno: "Js",
   },
-]" expected to contain: "[
+]" expected to include: "[
   {
     deno: "node",
   },
@@ -210,7 +210,7 @@ missing: [
 Deno.test("testingAssertStringContainsThrow", function (): void {
   let didThrow = false;
   try {
-    assertStringContains("Denosaurus from Jurassic", "Raptor");
+    assertStringIncludes("Denosaurus from Jurassic", "Raptor");
   } catch (e) {
     assert(
       e.message ===
@@ -715,7 +715,7 @@ Deno.test({
   fn(): void {
     assertEquals<string>("hello", "hello");
     assertNotEquals<number>(1, 2);
-    assertArrayContains<boolean>([true, false], [true]);
+    assertArrayIncludes<boolean>([true, false], [true]);
     const value = { x: 1 };
     assertStrictEquals<typeof value>(value, value);
     // eslint-disable-next-line @typescript-eslint/ban-types