diff --git a/testing/optics/index.test.ts b/testing/optics/index.test.ts
new file mode 100644
index 0000000..93c6eba
--- /dev/null
+++ b/testing/optics/index.test.ts
@@ -0,0 +1,31 @@
+import { assertEquals } from "https://deno.land/std/testing/asserts.ts";
+
+import * as I from "../../optics/index.ts";
+import * as O from "../../option.ts";
+
+Deno.test("Index indexArray", () => {
+  const index = I.indexArray<number>();
+  const { getOption, set } = index.index(1);
+
+  assertEquals(getOption([]), O.none);
+  assertEquals(getOption([1]), O.none);
+  assertEquals(getOption([1, 2]), O.some(2));
+
+  assertEquals(set(1)([]), []);
+  assertEquals(set(1)([1]), [1]);
+  assertEquals(set(1)([1, 2]), [1, 1]);
+});
+
+Deno.test("Index indexRecord", () => {
+  const index = I.indexRecord<number>();
+  const { getOption, set } = index.index("one");
+
+  assertEquals(getOption({}), O.none);
+  assertEquals(getOption({ two: 2 }), O.none);
+  assertEquals(getOption({ one: 1 }), O.some(1));
+
+  assertEquals(set(2)({}), {});
+  assertEquals(set(2)({ two: 2 }), { two: 2 });
+  assertEquals(set(2)({ one: 1 }), { one: 2 });
+  assertEquals(set(1)({ one: 1 }), { one: 1 });
+});