CustomViewTest.kt

package com.freshdigitable.sample

import android.content.Context
import android.os.Looper.getMainLooper
import android.view.ViewGroup
import android.widget.FrameLayout
import android.widget.TextView
import androidx.lifecycle.Lifecycle
import androidx.test.core.app.ActivityScenario
import androidx.test.core.app.ApplicationProvider
import androidx.test.ext.junit.runners.AndroidJUnit4
import com.google.common.truth.Truth.assertThat
import io.mockk.every
import io.mockk.just
import io.mockk.mockk
import io.mockk.runs
import io.mockk.verify
import org.junit.Test
import org.junit.runner.RunWith
import org.robolectric.Shadows.shadowOf
import org.robolectric.annotation.LooperMode

@RunWith(AndroidJUnit4::class)
@LooperMode(LooperMode.Mode.PAUSED)
class CustomViewTest {
    @Test
    fun hoge() {
        val context = ApplicationProvider.getApplicationContext<Context>()
        val sut = HogeView(context)
        val adapter = mockk<HogeView.Adapter>()
        sut.adapter = adapter

        sut.addView(TextView(context))

        assertThat(sut.childCount).isEqualTo(1)
        verify(exactly = 0) { adapter.onMeasure() }
        verify(exactly = 0) { adapter.onLayout() }
    }

    @Test
    fun hoge2() {
        val context = ApplicationProvider.getApplicationContext<Context>()
        val parent = FrameLayout(context)
        val sut = HogeView(context)
        val adapter = mockk<HogeView.Adapter>()
        sut.adapter = adapter
        parent.addView(sut)

        sut.addView(TextView(context))

        assertThat(sut.childCount).isEqualTo(1)
        verify(exactly = 0) { adapter.onMeasure() }
        verify(exactly = 0) { adapter.onLayout() }
    }

    @Test
    fun hoge3() {
        ActivityScenario.launch(MainActivity::class.java).moveToState(Lifecycle.State.RESUMED)
            .onActivity {
                val sut = HogeView(it)
                val adapter = mockk<HogeView.Adapter>().apply {
                    every { onMeasure() } just runs
                    every { onLayout() } just runs
                }
                sut.adapter = adapter
                it.setContentView(sut)
                shadowOf(getMainLooper()).idle()

                sut.addView(TextView(it))
                shadowOf(getMainLooper()).idle()

                assertThat(sut.childCount).isEqualTo(1)
                verify(exactly = 2) { adapter.onMeasure() }
                verify(exactly = 2) { adapter.onLayout() }
            }
    }

    @Test
    fun hoge4() {
        ActivityScenario.launch(MainActivity::class.java)
            .onActivity {
                val sut = HogeView(it)
                val adapter = mockk<HogeView.Adapter>().apply {
                    every { onMeasure() } just runs
                    every { onLayout() } just runs
                }
                sut.adapter = adapter
                it.setContentView(sut)
                shadowOf(getMainLooper()).idle()

                sut.addView(TextView(it))
                sut.addView(TextView(it))
                shadowOf(getMainLooper()).idle()

                assertThat(sut.childCount).isEqualTo(2)
                verify(exactly = 2) { adapter.onMeasure() }
                verify(exactly = 2) { adapter.onLayout() }
            }
    }

    @Test
    @LooperMode(LooperMode.Mode.LEGACY)
    fun hoge5() {
        ActivityScenario.launch(MainActivity::class.java).moveToState(Lifecycle.State.RESUMED)
            .onActivity {
                val sut = HogeView(it)
                val adapter = mockk<HogeView.Adapter>().apply {
                    every { onMeasure() } just runs
                    every { onLayout() } just runs
                }
                sut.adapter = adapter
                it.setContentView(sut)

                sut.addView(TextView(it))
                sut.addView(TextView(it))

                assertThat(sut.childCount).isEqualTo(2)
                verify(exactly = 3) { adapter.onMeasure() }
                verify(exactly = 3) { adapter.onLayout() }
            }
    }
}

class HogeView(context: Context) : ViewGroup(context) {
    var adapter: Adapter? = null

    override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec)
        adapter?.onMeasure()
    }

    override fun onLayout(changed: Boolean, l: Int, t: Int, r: Int, b: Int) {
        adapter?.onLayout()
    }

    interface Adapter {
        fun onMeasure()
        fun onLayout()
    }
}