A tool for testing Carousel. It can dynamically change the properties.

manual_test_carousel2.py

from kivy.lang import Builder
from kivy.factory import Factory
from kivy.app import runTouchApp


KV_CODE = '''
#:import random random
#:import Button kivy.uix.button.Button

<DebugCarousel@Carousel>:
    canvas.before:
        Clear:  # clear the instructions inherited from StencilView
    canvas.after:
        Clear:  # clear the instructions inherited from StencilView
        Color:
            rgba: 1, 1, 1, 1
        Line:
            dash_offset: 4
            dash_length: 2
            rectangle: [*self.pos, *self.size, ]

<Separator@Widget>:
    size: 1, 1
    canvas:
        Color:
            rgb: 1, 0, 1
        Rectangle:
            pos: self.pos
            size: self.size

BoxLayout:
    BoxLayout:
        size_hint_x: .2
        size_hint_min_x: 200
        orientation: 'vertical'
        Label:
            text: 'direction'
            color: 0, 1, 0, 1
        BoxLayout:
            CheckBox:
                group: 'direction'
                on_active: carousel.direction = 'left'
            Label:
                text: 'left'
        BoxLayout:
            CheckBox:
                group: 'direction'
                on_active: carousel.direction = 'right'
            Label:
                text: 'right'
        BoxLayout:
            CheckBox:
                group: 'direction'
                on_active: carousel.direction = 'top'
            Label:
                text: 'top'
        BoxLayout:
            CheckBox:
                group: 'direction'
                on_active: carousel.direction = 'bottom'
            Label:
                text: 'bottom'
        Separator:
            size_hint_y: None
        Label:
            text: 'loop'
            color: 0, 1, 0, 1
        Switch:
            id: loop_switch
            active: True
        Separator:
            size_hint_y: None
            height: 1
        Label:
            text: 'len(slides) == {}'.format(int(slider.value))
            color: 0, 1, 0, 1
        Slider:
            id: slider
            min: 0
            max: 4
            step: 1
            value: 0
        Separator:
            size_hint_y: None
            height: 1
        Label:
            text: 'methods'
            color: 0, 1, 0, 1
        Button:
            text: 'load_slide(not current_slide)'
            on_press:
                slides = carousel.slides[:]
                slides.remove(carousel.current_slide)
                carousel.load_slide(random.choice(slides))
        Button:
            text: 'load_slide(current_slide)'
            on_press: carousel.load_slide(carousel.current_slide)
        Button:
            text: 'load_next()'
            on_press: carousel.load_next()
        Button:
            text: 'load_previous()'
            on_press: carousel.load_previous()
    Separator:
        size_hint_x: None
    FloatLayout:
        DebugCarousel:
            id: carousel
            size_hint: .2, .2
            pos_hint: {'center': (.5, .5, ), }
            loop: loop_switch.active
'''

root = Builder.load_string(KV_CODE)
carousel = root.ids.carousel
carousel.bind(index=lambda __, value: print('index:', value))

def update_carousels_slides(slider, value):
    from kivy.uix.button import Button
    carousel.clear_widgets()
    for i in range(int(value)):
        carousel.add_widget(Button(text=str(i), font_size=50))
slider = root.ids.slider
slider.bind(value=update_carousels_slides)
slider.value = 2

runTouchApp(root)