From 9eca71caa1674c31f9cc5d4e86c03f10b59e0a00 Mon Sep 17 00:00:00 2001
From: Rob Waller <rdwaller1984@gmail.com>
Date: Tue, 14 Jul 2020 19:41:05 +0100
Subject: [PATCH] fix(std/testing): assertThrows inheritance (#6623)

---
 std/testing/asserts.ts      |  4 ++--
 std/testing/asserts_test.ts | 24 ++++++++++++++++++++++--
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/std/testing/asserts.ts b/std/testing/asserts.ts
index b1164090d4..2a13581435 100644
--- a/std/testing/asserts.ts
+++ b/std/testing/asserts.ts
@@ -394,7 +394,7 @@ export function assertThrows<T = void>(
     if (e instanceof Error === false) {
       throw new AssertionError("A non-Error object was thrown.");
     }
-    if (ErrorClass && !(Object.getPrototypeOf(e) === ErrorClass.prototype)) {
+    if (ErrorClass && !(e instanceof ErrorClass)) {
       msg = `Expected error to be instance of "${ErrorClass.name}", but was "${
         e.constructor.name
       }"${msg ? `: ${msg}` : "."}`;
@@ -438,7 +438,7 @@ export async function assertThrowsAsync<T = void>(
     if (e instanceof Error === false) {
       throw new AssertionError("A non-Error object was thrown or rejected.");
     }
-    if (ErrorClass && !(Object.getPrototypeOf(e) === ErrorClass.prototype)) {
+    if (ErrorClass && !(e instanceof ErrorClass)) {
       msg = `Expected error to be instance of "${ErrorClass.name}", but got "${
         e.name
       }"${msg ? `: ${msg}` : "."}`;
diff --git a/std/testing/asserts_test.ts b/std/testing/asserts_test.ts
index c7fa5a737f..c3059ebac4 100644
--- a/std/testing/asserts_test.ts
+++ b/std/testing/asserts_test.ts
@@ -275,12 +275,12 @@ Deno.test("testingAssertFailWithWrongErrorClass", function (): void {
         (): void => {
           fail("foo");
         },
-        Error,
+        TypeError,
         "Failed assertion: foo"
       );
     },
     AssertionError,
-    `Expected error to be instance of "Error", but was "AssertionError"`
+    `Expected error to be instance of "TypeError", but was "AssertionError"`
   );
 });
 
@@ -626,3 +626,23 @@ Deno.test("assert diff formatting", () => {
 ]`
   );
 });
+
+Deno.test("Assert Throws Parent Error", () => {
+  assertThrows(
+    () => {
+      throw new AssertionError("Fail!");
+    },
+    Error,
+    "Fail!"
+  );
+});
+
+Deno.test("Assert Throws Async Parent Error", () => {
+  assertThrowsAsync(
+    () => {
+      throw new AssertionError("Fail!");
+    },
+    Error,
+    "Fail!"
+  );
+});