packages/flutter/test/foundation/basic_types_test.dart

// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'package:flutter/src/foundation/basic_types.dart';
import 'package:flutter_test/flutter_test.dart';

void main() {
  group('lerp Duration', () {
    test('linearly interpolates between positive Durations', () {
      expect(
        lerpDuration(const Duration(seconds: 1), const Duration(seconds: 2), 0.5),
        const Duration(milliseconds: 1500),
      );
    });

    test('linearly interpolates between negative Durations', () {
      expect(
        lerpDuration(const Duration(seconds: -1), const Duration(seconds: -2), 0.5),
        const Duration(milliseconds: -1500),
      );
    });

    test('linearly interpolates between positive and negative Durations', () {
      expect(
        lerpDuration(const Duration(seconds: -1), const Duration(seconds:2), 0.5),
        const Duration(milliseconds: 500),
      );
    });

    test('starts at first Duration', () {
      expect(
        lerpDuration(const Duration(seconds: 1), const Duration(seconds: 2), 0),
        const Duration(seconds: 1),
      );
    });

    test('ends at second Duration', () {
      expect(
        lerpDuration(const Duration(seconds: 1), const Duration(seconds: 2), 1),
        const Duration(seconds: 2),
      );
    });

    test('time values beyond 1.0 have a multiplier effect', () {
      expect(
        lerpDuration(const Duration(seconds: 1), const Duration(seconds: 2), 5),
        const Duration(seconds: 6),
      );

      expect(
        lerpDuration(const Duration(seconds: -1), const Duration(seconds: -2), 5),
        const Duration(seconds: -6),
      );
    });
  });
}