Solution: GUI View Hierarchy Simulation

open class View(
    val id: String,
    var isVisible: Boolean
) {
    fun show() {
        isVisible = true
    }

    fun hide() {
        isVisible = false
    }
}

class TextView(
    id: String,
    var text: String
) : View(id, true)

class Toggle(
    id: String,
) : View(id, true) {
    var isOn: Boolean = false

    fun click() {
        isOn = !isOn
    }
}

Example solution in playground

import junit.framework.TestCase.assertFalse
import junit.framework.TestCase.assertTrue
import org.junit.Test
import kotlin.test.assertEquals

open class View(
    val id: String,
    var isVisible: Boolean
) {
    fun show() {
        isVisible = true
    }

    fun hide() {
        isVisible = false
    }
}

class TextView(
    id: String,
    var text: String
) : View(id, true)

class Toggle(
    id: String,
) : View(id, true) {
    var isOn: Boolean = false

    fun click() {
        isOn = !isOn
    }
}

fun main() {
    val view = View(
        id = "v1",
        isVisible = false,
    )
    println(view.id) // v1
    println(view.isVisible) // false
    
    val textView = TextView(
        id = "tv1",
        text = "Hello, World!",
    )
    println(textView.id) // tv1
    println(textView.text) // Hello, World!
    println(textView.isVisible) // true
    
    textView.text = "Welcome to Kotlin!"
    println(textView.text) // Welcome to Kotlin!
    
    textView.hide()
    println(textView.isVisible) // false
    
    val toggle = Toggle(
        id = "toggle1",
    )
    println(toggle.id) // toggle1
    
    println(toggle.isOn) // false
    toggle.click()
    println(toggle.isOn) // true
    
    println(toggle.isVisible) // true
    toggle.hide()
    println(toggle.isVisible) // false
    toggle.show()
    println(toggle.isVisible) // true
}

class GuiTests {

    @Test
    fun `view show should set isVisible to true`() {
        val view = View("view1", false)
        view.show()
        assertTrue(view.isVisible)
    }

    @Test
    fun `view hide should set isVisible to false`() {
        val view = View("view2", true)
        view.hide()
        assertFalse(view.isVisible)
    }

    @Test
    fun `toggle click should toggle isOn state`() {
        val toggle = Toggle("toggle1")
        toggle.click()
        assertTrue(toggle.isOn)
        toggle.click()
        assertFalse(toggle.isOn)
    }

    @Test
    fun `text view setText should update text property`() {
        val textView = TextView("textView1", "Hello")
        textView.text = "World"
        assertEquals("World", textView.text)
    }

    @Test
    fun `toggle should inherit properties from view`() {
        val toggle = Toggle("toggle2")
        assertTrue(toggle.isVisible)
        toggle.hide()
        assertFalse(toggle.isVisible)
    }

    @Test
    fun `text view should inherit properties from view`() {
        val textView = TextView("textView2", "Hello")
        assertTrue(textView.isVisible)
    }

    @Test
    fun `toggle should start with isOn set to false`() {
        val toggle = Toggle("toggle3")
        assertFalse(toggle.isOn)
    }

    @Test
    fun `toggle should toggle isOn state correctly`() {
        val toggle = Toggle("toggle4")
        toggle.click()
        assertTrue(toggle.isOn)
        toggle.click()
        assertFalse(toggle.isOn)
        toggle.click()
        assertTrue(toggle.isOn)
    }

    @Test
    fun `view show and hide interactions`() {
        val view = View("view3", false)
        view.show()
        assertTrue(view.isVisible)
        view.hide()
        assertFalse(view.isVisible)
    }

    @Test
    fun `text view setText and visibility interactions`() {
        val textView = TextView("textView3", "Hello")
        textView.text = "World"
        assertEquals("World", textView.text)
        textView.hide()
        assertFalse(textView.isVisible)
    }
}