1 files changed, 15 insertions, 0 deletions
diff --git a/std/io/writers_test.ts b/std/io/writers_test.ts
new file mode 100644
index 000000000..decf611f1
--- /dev/null
+++ b/std/io/writers_test.ts
@@ -0,0 +1,15 @@
+const { copy } = Deno;
+import { test } from "../testing/mod.ts";
+import { assertEquals } from "../testing/asserts.ts";
+import { StringWriter } from "./writers.ts";
+import { StringReader } from "./readers.ts";
+import { copyN } from "./ioutil.ts";
+
+test(async function ioStringWriter(): Promise<void> {
+  const w = new StringWriter("base");
+  const r = new StringReader("0123456789");
+  await copyN(w, r, 4);
+  assertEquals(w.toString(), "base0123");
+  await copy(w, r);
+  assertEquals(w.toString(), "base0123456789");
+});