avoid using same port number for test (#4147)

1 files changed, 20 insertions, 0 deletions

diff --git a/std/http/test_util.ts b/std/http/test_util.ts
new file mode 100644
index 000000000..c86a339a7
--- /dev/null
+++ b/std/http/test_util.ts
@@ -0,0 +1,20 @@
+import { assert } from "../testing/asserts.ts";
+
+function* portIterator(): IterableIterator<number> {
+  // use 55001 ~ 65535 (rest (49152~55000) are for cli/js)
+  let i = 55001;
+  while (true) {
+    yield i;
+    i++;
+    if (i > 65535) {
+      i = 55001;
+    }
+  }
+}
+const it = portIterator();
+/** Obtain (maybe) safe port number for net tests */
+export function randomPort(): number {
+  const { value } = it.next();
+  assert(value != null);
+  return value;
+}