feat: type declarations for new Set methods (#23090)

Closes #22851

1 files changed, 7 insertions, 0 deletions

diff --git a/tests/unit/esnext_test.ts b/tests/unit/esnext_test.ts
index 6b2334f42..cb40cc241 100644
--- a/tests/unit/esnext_test.ts
+++ b/tests/unit/esnext_test.ts
@@ -41,3 +41,10 @@ Deno.test(function intlListFormat() {
     { type: "element", value: "golang" },
   ]);
 });
+
+Deno.test(function setUnion() {
+  const a = new Set([1, 2, 3]);
+  const b = new Set([3, 4, 5]);
+  const union = a.union(b);
+  assertEquals(union, new Set([1, 2, 3, 4, 5]));
+});