std/collections/unstable_drop_last_while_test.ts

// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
import { dropLastWhile } from "./unstable_drop_last_while.ts";
import { assertEquals } from "@std/assert";

Deno.test("(unstable) dropLastWhile() handles num array", () => {
  const values = [20, 33, 44];
  const actual = dropLastWhile(values, (i) => i > 30);
  assertEquals(actual, [20]);
});

Deno.test("(unstable) dropLastWhile() does not mutate the input array", () => {
  const array = [1, 2, 3, 4, 5, 6];
  const actual = dropLastWhile(array, (i) => i > 4);
  assertEquals(actual, [1, 2, 3, 4]);
  assertEquals(array, [1, 2, 3, 4, 5, 6]);
});

Deno.test("(unstable) dropLastWhile() handles negatives", () => {
  const array = [-1, -2, -3, -4, -5, -6];
  const actual = dropLastWhile(array, (i) => i < -4);
  assertEquals(actual, [-1, -2, -3, -4]);
});

Deno.test("(unstable) dropLastWhile() handles empty input returns empty array", () => {
  const array: number[] = [];
  const actual = dropLastWhile(array, (i) => i > 4);
  assertEquals(actual, []);
});

Deno.test("(unstable) dropLastWhile() returns same array when the last element doesn't get dropped", () => {
  const array = [40, 30, 20];
  const actual = dropLastWhile(array, (i) => i > 40);
  assertEquals(actual, [40, 30, 20]);
});

Deno.test("(unstable) dropLastWhile() returns empty array when all elements get dropped", () => {
  const array = [20, 30, 20];
  const actual = dropLastWhile(array, (i) => i < 40);
  assertEquals(actual, []);
});

Deno.test("(unstable) dropLastWhile() handles a string", () => {
  const values = "hello there world";
  const actual = dropLastWhile(values, (i) => i !== " ");
  assertEquals(actual, "hello there ".split(""));
});

Deno.test("(unstable) dropLastWhile() handles a Set", () => {
  const values = new Set([20, 33, 44]);
  const actual = dropLastWhile(values, (i) => i > 30);
  assertEquals(actual, [20]);
});

Deno.test("(unstable) dropLastWhile() handles a Map", () => {
  const values = new Map([
    ["a", 20],
    ["b", 33],
    ["c", 44],
  ]);
  const actual = dropLastWhile(values, ([_k, v]) => v > 30);
  assertEquals(actual, [["a", 20]]);
});

Deno.test("(unstable) dropLastWhile() handles a generator", () => {
  function* gen() {
    yield 20;
    yield 33;
    yield 44;
  }
  const actual = dropLastWhile(gen(), (i) => i > 30);
  assertEquals(actual, [20]);
});