diff --git a/derivations.ts b/derivations.ts
index bd8665f..f97a797 100644
--- a/derivations.ts
+++ b/derivations.ts
@@ -1,7 +1,27 @@
 import type * as TC from "./type_classes.ts";
 import type { Kind, URIS } from "./hkt.ts";
 
-import { pipe } from "./fns.ts";
+import { identity, pipe } from "./fns.ts";
+
+/*******************************************************************************
+ * Module Derivations
+ ******************************************************************************/
+
+/**
+ * Derive Monad module from of and chain
+ */
+// export const createMonad = <URI extends URIS>(
+//   { of, chain }: Pick<TC.Monad<URI>, "of" | "chain">,
+// ): TC.Monad<URI> => {
+//   const Monad: TC.Monad<URI> = {
+//     of,
+//     ap: (tfai) => (ta) => pipe(tfai, chain((fab) => pipe(ta, Monad.map(fab)))),
+//     map: (fai) => (ta) => pipe(ta, chain((a) => of(fai(a)))),
+//     chain,
+//     join: chain(identity),
+//   };
+//   return Monad;
+// };
 
 /*******************************************************************************
  * Do notation Derivation
diff --git a/testing/these.test.ts b/testing/these.test.ts
new file mode 100644
index 0000000..a4e56e0
--- /dev/null
+++ b/testing/these.test.ts
@@ -0,0 +1,134 @@
+import { assertEquals } from "https://deno.land/std/testing/asserts.ts";
+
+import * as T from "../these.ts";
+import * as O from "../option.ts";
+import { _, pipe } from "../fns.ts";
+import { semigroupSum } from "../semigroup.ts";
+
+import * as AS from "./assert.ts";
+
+Deno.test("These left", () => {
+  assertEquals(T.left(1), { tag: "Left", left: 1 });
+});
+
+Deno.test("These right", () => {
+  assertEquals(T.right(1), { tag: "Right", right: 1 });
+});
+
+Deno.test("These both", () => {
+  assertEquals(T.both(0, 1), { tag: "Both", left: 0, right: 1 });
+});
+
+Deno.test("These fold", () => {
+  const fold = T.fold(AS.add, AS.add, (a, b) => a + b);
+  assertEquals(fold(T.left(1)), 2);
+  assertEquals(fold(T.right(2)), 3);
+  assertEquals(fold(T.both(2, 2)), 4);
+});
+
+Deno.test("These isLeft", () => {
+  assertEquals(T.isLeft(T.left(1)), true);
+  assertEquals(T.isLeft(T.right(1)), false);
+  assertEquals(T.isLeft(T.both(1, 1)), false);
+});
+
+Deno.test("These isRight", () => {
+  assertEquals(T.isRight(T.left(1)), false);
+  assertEquals(T.isRight(T.right(1)), true);
+  assertEquals(T.isRight(T.both(1, 1)), false);
+});
+
+Deno.test("These isBoth", () => {
+  assertEquals(T.isBoth(T.left(1)), false);
+  assertEquals(T.isBoth(T.right(1)), false);
+  assertEquals(T.isBoth(T.both(1, 1)), true);
+});
+
+Deno.test("These getShow", () => {
+  const f = { show: (n: number) => n.toString() };
+  const { show } = T.getShow(f, f);
+  assertEquals(show(T.left(1)), "Left(1)");
+  assertEquals(show(T.right(1)), "Right(1)");
+  assertEquals(show(T.both(1, 1)), "Both(1, 1)");
+});
+
+Deno.test("These getSemigroup", () => {
+  const Semigroup = T.getSemigroup(semigroupSum, semigroupSum);
+  const concat = Semigroup.concat;
+  const cl = concat(T.left(1));
+  const cr = concat(T.right(1));
+  const cb = concat(T.both(1, 1));
+  assertEquals(cl(T.left(1)), T.left(2));
+  assertEquals(cl(T.right(1)), T.both(1, 1));
+  assertEquals(cl(T.both(1, 1)), T.both(2, 1));
+  assertEquals(cr(T.left(1)), T.both(1, 1));
+  assertEquals(cr(T.right(1)), T.right(2));
+  assertEquals(cr(T.both(1, 1)), T.both(1, 2));
+  assertEquals(cb(T.left(1)), T.both(2, 1));
+  assertEquals(cb(T.right(1)), T.both(1, 2));
+  assertEquals(cb(T.both(1, 1)), T.both(2, 2));
+});
+
+Deno.test("These Functor", () => {
+  AS.assertFunctor(T.Functor, {
+    ta: T.right(1),
+    fai: AS.add,
+    fij: AS.multiply,
+  });
+});
+
+Deno.test("These Bifunctor", () => {
+  AS.assertBifunctor(T.Bifunctor, {
+    tab: T.both(1, 1),
+    fai: AS.add,
+    fij: AS.multiply,
+    fbx: AS.multiply,
+    fxy: AS.add,
+  });
+});
+
+Deno.test("These Foldable", () => {
+  AS.assertFoldable(T.Foldable, {
+    a: 0,
+    tb: T.right(1),
+    faia: (a: number, i: number) => a + i,
+  });
+});
+
+Deno.test("These bimap", () => {
+  const bimap = T.bimap(AS.add, AS.add);
+  assertEquals(bimap(T.left(1)), T.left(2));
+  assertEquals(bimap(T.right(1)), T.right(2));
+  assertEquals(bimap(T.both(1, 1)), T.both(2, 2));
+});
+
+Deno.test("These mapLeft", () => {
+  const mapLeft = T.mapLeft(AS.add);
+  assertEquals(mapLeft(T.left(1)), T.left(2));
+  assertEquals(mapLeft(T.right(1)), T.right(1));
+  assertEquals(mapLeft(T.both(1, 1)), T.both(2, 1));
+});
+
+Deno.test("These map", () => {
+  const map = T.map(AS.add);
+  assertEquals(map(T.left(1)), T.left(1));
+  assertEquals(map(T.right(1)), T.right(2));
+  assertEquals(map(T.both(1, 1)), T.both(1, 2));
+});
+
+Deno.test("These reduce", () => {
+  const reduce = T.reduce((n: number, m: number) => n + m, 0);
+  assertEquals(reduce(T.left(1)), 0);
+  assertEquals(reduce(T.right(1)), 1);
+  assertEquals(reduce(T.both(1, 1)), 1);
+});
+
+Deno.test("These traverse", () => {
+  const t1 = T.traverse(O.Applicative);
+  const t2 = t1((n: number) => n === 0 ? O.none : O.some(n));
+  assertEquals(t2(T.left(1)), O.some(T.left(1)));
+  assertEquals(t2(T.right(0)), O.none);
+  assertEquals(t2(T.right(1)), O.some(T.right(1)));
+  assertEquals(t2(T.both(1, 0)), O.none);
+  assertEquals(t2(T.both(1, 1)), O.some(T.both(1, 1)));
+});
diff --git a/these.ts b/these.ts
index 32e7598..66be55d 100644
--- a/these.ts
+++ b/these.ts
@@ -2,8 +2,7 @@ import type * as HKT from "./hkt.ts";
 import type * as TC from "./type_classes.ts";
 
 import * as E from "./either.ts";
-import { identity, pipe } from "./fns.ts";
-import { createMonad } from "./derivations.ts";
+import { flow, identity, pipe } from "./fns.ts";
 
 /*******************************************************************************
  * Types
@@ -163,18 +162,18 @@ export const Traversable: TC.Traversable<URI> = {
   map: Functor.map,
   traverse: (A) =>
     (faub) =>
-      (ta) =>
-        isLeft(ta)
-          ? A.of(ta)
-          : isRight(ta)
-          ? pipe(faub(ta.right), A.map(right))
-          : pipe(faub(ta.right), A.map((r) => both(ta.left, r))),
+      fold(
+        flow(left, A.of),
+        flow(faub, A.map((b) => right(b))),
+        // deno-lint-ignore no-explicit-any
+        (l, r) => pipe(r, faub, A.map((b) => both(l, b))) as any,
+      ),
 };
 
 /*******************************************************************************
  * Pipeables
  ******************************************************************************/
 
-export const { bimap } = Bifunctor;
+export const { bimap, mapLeft } = Bifunctor;
 
-export const { reduce, traverse } = Traversable;
+export const { map, reduce, traverse } = Traversable;