assert-async

src/debug.test.ts

@@ -5,6 +5,7 @@ import {
   spy,
 } from "https://deno.land/[email protected]/testing/mock.ts";
 
+import { assertEquals } from "https://deno.land/[email protected]/assert/assert_equals.ts";
 import { assertThrows } from "https://deno.land/[email protected]/testing/asserts.ts";
 import { sleep } from "./time.ts";
 
@@ -45,8 +46,22 @@ Deno.test("asyncTimeit with args", async () => {
 
 Deno.test("assert", () => {
   const err = "not greater than 7";
+  const condition = (x: number) => x > 7;
   assertThrows(() => {
-    assert((x: number) => x > 7, err)(3);
+    assert(condition, err)(3);
   });
-  assert((x: number) => x > 7, err)(10);
+  assert(condition, err)(10);
+});
+
+Deno.test("assert async", async () => {
+  const err = "not greater than 7";
+  const condition = (x: number) => Promise.resolve(x > 7);
+  let thrown = false;
+  try {
+    await assert(condition, err)(3);
+  } catch (_) {
+    thrown = true;
+  }
+  assertEquals(thrown, true);
+  await assert(condition, err)(10);
 });

src/debug.ts

@@ -1,7 +1,8 @@
 import { Func, ReturnTypeUnwrapped } from "./typing.ts";
 
 import { currentLocation } from "./trace.ts";
-import { sideEffect } from "./composition.ts";
+import { pairRight } from "./juxt.ts";
+import { pipe } from "./composition.ts";
 
 export const sideLog = <T>(x: T) => {
   console.log(currentLocation(3), x);
@@ -62,7 +63,14 @@ export const timeit = <F extends Func>(
     return result;
   }) as F;
 
-export const assert = <T>(condition: (_: T) => boolean, errorMessage: string) =>
-  sideEffect((x: T) => {
-    if (!condition(x)) throw new Error(errorMessage);
-  });
+export const assert = <T>(
+  condition: (_: T) => boolean | Promise<boolean>,
+  errorMessage: string,
+) =>
+  pipe(
+    pairRight(condition),
+    ([value, passed]) => {
+      if (!passed) throw new Error(errorMessage);
+      return value;
+    },
+  );