std/collections/intersect_test.ts

// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.

import { assertEquals } from "@std/assert";
import { intersect } from "./intersect.ts";

function intersectTest<I>(
  input: Array<Array<I>>,
  expected: Array<I>,
  message?: string,
) {
  const actual = intersect(...input);
  assertEquals(actual, expected, message);
}

Deno.test({
  name: "intersect() handles no mutation",
  fn() {
    const arrayA = [1, 2, 3];
    const arrayB = [3, 4, 5];
    intersect(arrayA, arrayB);

    assertEquals(arrayA, [1, 2, 3]);
    assertEquals(arrayB, [3, 4, 5]);
  },
});

Deno.test({
  name: "intersect() handles empty input",
  fn() {
    intersectTest([], []);
  },
});

Deno.test({
  name: "intersect() handles empty arrays",
  fn() {
    intersectTest([[], []], []);
  },
});

Deno.test({
  name: "intersect() handles one side empty",
  fn() {
    intersectTest([[], ["a", "b", "c"]], []);
    intersectTest([["a", "b", "c"], []], []);
  },
});

Deno.test({
  name: "intersect() handles empty result",
  fn() {
    intersectTest([["a", "b", "c"], ["d", "e", "f"]], []);
  },
});

Deno.test({
  name: "intersect() handles one or more items in intersection",
  fn() {
    intersectTest([["a", "b"], ["b", "c"]], ["b"]);
    intersectTest([["a", "b", "c", "d"], ["c", "d", "e", "f"]], ["c", "d"]);
  },
});

Deno.test({
  name: "intersect() handles duplicates",
  fn() {
    intersectTest([["a", "b", "c", "b"], ["b", "c"]], ["b", "c"]);
    intersectTest([["a", "b"], ["b", "b", "c", "c"]], ["b"]);
  },
});

Deno.test({
  name: "intersect() handles more than two inputs",
  fn() {
    intersectTest(
      [
        ["a", "b"],
        ["b", "c"],
        ["s", "b"],
        ["b", "b"],
      ],
      ["b"],
    );
    intersectTest(
      [
        [1],
        [1],
        [2],
      ],
      [],
    );
    intersectTest(
      [
        [true, false],
        [true, false],
        [true],
      ],
      [true],
    );
  },
});

Deno.test({
  name: "intersect() handles objects",
  fn() {
    intersectTest<Record<string, string>>([
      [{ foo: "bar" }, { bar: "baz" }],
      [{ fruit: "banana" }],
    ], []);

    const obj = { bar: "baz" };
    intersectTest<Record<string, string>>([
      [{ foo: "bar" }, obj],
      [obj],
    ], [obj]);
    intersectTest<Record<string, string>>([
      [{ foo: "bar" }, { bar: "baz" }],
      [{ bar: "banana" }],
    ], []);
  },
});

Deno.test({
  name: "intersect() handles functions",
  fn() {
    intersectTest([
      [() => {}, () => null],
      [() => NaN],
    ], []);

    const emptyObjectFunction = () => {};
    intersectTest([
      [emptyObjectFunction, () => null],
      [emptyObjectFunction],
    ], [emptyObjectFunction]);
    intersectTest([
      [(a: number, b: number) => a + b, () => null],
      [(a: number, b: number) => a - b],
    ], []);
  },
});