ItemsAdapterTest.java

package com.artemzin.qualitymatters.ui.adapters;

import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

import com.artemzin.qualitymatters.QualityMattersRobolectricUnitTestRunner;
import com.artemzin.qualitymatters.R;
import com.artemzin.qualitymatters.api.entities.Item;
import com.artemzin.qualitymatters.models.QualityMattersImageLoader;

import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;

import java.util.List;

import static java.util.Arrays.asList;
import static java.util.Collections.emptyList;
import static org.assertj.core.api.Assertions.assertThat;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.verify;
import static org.mockito.Mockito.verifyNoMoreInteractions;
import static org.mockito.Mockito.when;

@RunWith(QualityMattersRobolectricUnitTestRunner.class)
public class ItemsAdapterTest {
    private LayoutInflater layoutInflater;
    private QualityMattersImageLoader imageLoader;
    private ItemsAdapter adapter;

    @Before
    public void beforeEachTest() {
        layoutInflater = mock(LayoutInflater.class);
        imageLoader = mock(QualityMattersImageLoader.class);
        adapter = new ItemsAdapter(layoutInflater, imageLoader);
    }

    @Test
    public void getItemCount_shouldBeZeroByDefault() {
        assertThat(adapter.getItemCount()).isEqualTo(0);
    }

    @Test
    public void getItemCount_shouldReturnCorrectValueAfterSetData() {
        adapter.setData(asList(mock(Item.class), mock(Item.class)));
        assertThat(adapter.getItemCount()).isEqualTo(2);
    }

    @Test
    public void setData_shouldNotifyObserversAboutChange() {
        RecyclerView.AdapterDataObserver observer = mock(RecyclerView.AdapterDataObserver.class);
        adapter.registerAdapterDataObserver(observer);

        adapter.setData(emptyList());
        verify(observer).onChanged();
        verifyNoMoreInteractions(observer);
    }

    @Test
    public void onCreateViewHolder_shouldCreateViewHolder() {
        ViewGroup parent = mock(ViewGroup.class);
        View itemView = mock(View.class);

        ImageView imageView = mock(ImageView.class);
        when(itemView.findViewById(R.id.list_item_image_view)).thenReturn(imageView);

        TextView titleTextView = mock(TextView.class);
        when(itemView.findViewById(R.id.list_item_title_text_view)).thenReturn(titleTextView);

        TextView shortDescriptionTextView = mock(TextView.class);
        when(itemView.findViewById(R.id.list_item_short_description_text_view)).thenReturn(shortDescriptionTextView);

        when(layoutInflater.inflate(R.layout.list_item, parent, false)).thenReturn(itemView);

        ItemViewHolder viewHolder = adapter.onCreateViewHolder(parent, 0);
        verify(layoutInflater).inflate(R.layout.list_item, parent, false);

        assertThat(viewHolder.itemView).isSameAs(itemView);
        // Also, we don't expect exceptions here.
    }

    @Test
    public void onBindViewHolder_shouldBindItemsToTheViewHolders() {
        List<Item> items = asList(
                Item.builder().id("1").imagePreviewUrl("https://url1").title("t1").shortDescription("s1").build(),
                Item.builder().id("2").imagePreviewUrl("https://url2").title("t2").shortDescription("s2").build(),
                Item.builder().id("3").imagePreviewUrl("https://url3").title("t3").shortDescription("s3").build()
        );

        adapter.setData(items);

        for (int position = 0, size = items.size(); position < size; position++) {
            ItemViewHolder itemViewHolder = mock(ItemViewHolder.class);
            adapter.onBindViewHolder(itemViewHolder, position);

            verify(itemViewHolder).bind(items.get(position));
        }
    }
}