feat(std/testing): add assertNotMatch (#6775)

std/testing/README.md

@@ -21,6 +21,8 @@ pretty-printed diff of failing assertion.
 - `assertStringContains()` - Make an assertion that `actual` contains
   `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
   `expected` values.
 - `assertThrows()` - Expects the passed `fn` to throw. If `fn` does not throw,

std/testing/asserts.ts

@@ -409,6 +409,23 @@ export function assertMatch(
   }
 }
 
+/**
+ * Make an assertion that `actual` not match RegExp `expected`. If match
+ * then thrown
+ */
+export function assertNotMatch(
+  actual: string,
+  expected: RegExp,
+  msg?: string,
+): void {
+  if (expected.test(actual)) {
+    if (!msg) {
+      msg = `actual: "${actual}" expected to not match: "${expected}"`;
+    }
+    throw new AssertionError(msg);
+  }
+}
+
 /**
  * Forcefully throws a failed assertion
  */

std/testing/asserts_test.ts

@@ -6,6 +6,7 @@ import {
   assertStringContains,
   assertArrayContains,
   assertMatch,
+  assertNotMatch,
   assertEquals,
   assertStrictEquals,
   assertNotStrictEquals,
@@ -232,6 +233,25 @@ Deno.test("testingAssertStringMatchingThrows", function (): void {
   assert(didThrow);
 });
 
+Deno.test("testingAssertStringNotMatching", function (): void {
+  assertNotMatch("foobar.deno.com", RegExp(/[a-zA-Z]+@[a-zA-Z]+.com/));
+});
+
+Deno.test("testingAssertStringNotMatchingThrows", function (): void {
+  let didThrow = false;
+  try {
+    assertNotMatch("Denosaurus from Jurassic", RegExp(/from/));
+  } catch (e) {
+    assert(
+      e.message ===
+        `actual: "Denosaurus from Jurassic" expected to not match: "/from/"`,
+    );
+    assert(e instanceof AssertionError);
+    didThrow = true;
+  }
+  assert(didThrow);
+});
+
 Deno.test("testingAssertsUnimplemented", function (): void {
   let didThrow = false;
   try {