[bun.js] Add `Bun.nanoseconds()` to report time in nanos

1 files changed, 18 insertions, 0 deletions

diff --git a/integration/bunjs-only-snippets/performance.test.js b/integration/bunjs-only-snippets/performance.test.js
new file mode 100644
index 000000000..5e8520638
--- /dev/null
+++ b/integration/bunjs-only-snippets/performance.test.js
@@ -0,0 +1,18 @@
+import { expect, it } from "bun:test";
+
+it("performance.now() should be monotonic", () => {
+  const first = performance.now();
+  const second = performance.now();
+  const third = performance.now();
+  const fourth = performance.now();
+  const fifth = performance.now();
+  const sixth = performance.now();
+  expect(first < second).toBe(true);
+  expect(second < third).toBe(true);
+  expect(third < fourth).toBe(true);
+  expect(fourth < fifth).toBe(true);
+  expect(fifth < sixth).toBe(true);
+  expect(Bun.nanoseconds() > 0).toBe(true);
+  expect(Bun.nanoseconds() > sixth).toBe(true);
+  expect(typeof Bun.nanoseconds() === "number").toBe(true);
+});