react-native/Libraries/Lists/__tests__/VirtualizeUtils-test.js

/**
 * Copyright (c) 2015-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *
 *
 * @format
 * @emails oncall+react_native
 */
'use strict';

const {elementsThatOverlapOffsets, newRangeCount} = require('VirtualizeUtils');

describe('newRangeCount', function() {
  it('handles subset', function() {
    expect(newRangeCount({first: 1, last: 4}, {first: 2, last: 3})).toBe(0);
  });
  it('handles forward disjoint set', function() {
    expect(newRangeCount({first: 1, last: 4}, {first: 6, last: 9})).toBe(4);
  });
  it('handles reverse disjoint set', function() {
    expect(newRangeCount({first: 6, last: 8}, {first: 1, last: 4})).toBe(4);
  });
  it('handles superset', function() {
    expect(newRangeCount({first: 1, last: 4}, {first: 0, last: 5})).toBe(2);
  });
  it('handles end extension', function() {
    expect(newRangeCount({first: 1, last: 4}, {first: 1, last: 8})).toBe(4);
  });
  it('handles front extension', function() {
    expect(newRangeCount({first: 1, last: 4}, {first: 0, last: 4})).toBe(1);
  });
  it('handles forward insersect', function() {
    expect(newRangeCount({first: 1, last: 4}, {first: 3, last: 6})).toBe(2);
  });
  it('handles reverse intersect', function() {
    expect(newRangeCount({first: 3, last: 6}, {first: 1, last: 4})).toBe(2);
  });
});

describe('elementsThatOverlapOffsets', function() {
  it('handles fixed length', function() {
    const offsets = [0, 250, 350, 450];
    function getFrameMetrics(index: number) {
      return {
        length: 100,
        offset: 100 * index,
      };
    }
    expect(elementsThatOverlapOffsets(offsets, 100, getFrameMetrics)).toEqual([
      0,
      2,
      3,
      4,
    ]);
  });
  it('handles variable length', function() {
    const offsets = [150, 250, 900];
    const frames = [
      {offset: 0, length: 50},
      {offset: 50, length: 200},
      {offset: 250, length: 600},
      {offset: 850, length: 100},
      {offset: 950, length: 150},
    ];
    expect(
      elementsThatOverlapOffsets(offsets, frames.length, ii => frames[ii]),
    ).toEqual([1, 1, 3]);
  });
  it('handles out of bounds', function() {
    const offsets = [150, 900];
    const frames = [
      {offset: 0, length: 50},
      {offset: 50, length: 150},
      {offset: 250, length: 100},
    ];
    expect(
      elementsThatOverlapOffsets(offsets, frames.length, ii => frames[ii]),
    ).toEqual([1]);
  });
  it('errors on non-increasing offsets', function() {
    const offsets = [150, 50];
    const frames = [
      {offset: 0, length: 50},
      {offset: 50, length: 150},
      {offset: 250, length: 100},
    ];
    expect(() => {
      elementsThatOverlapOffsets(offsets, frames.length, ii => frames[ii]);
    }).toThrowErrorMatchingSnapshot();
  });
});