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Testing Bitmap CenterInside Transformation in bumptech/glide

This test suite validates the CenterInside bitmap transformation functionality in Glide, an image loading library for Android. The tests verify the behavior of bitmap scaling and resource management when applying center-inside transformations to images.

Test Coverage Overview

The test suite provides comprehensive coverage of the CenterInside transformation class, focusing on resource handling and size transformations.

Tests size matching scenarios for exact dimensions
Validates behavior for smaller and larger target sizes
Verifies resource recycling policies
Ensures proper equality comparison functionality

Implementation Analysis

The testing approach utilizes JUnit and Robolectric for Android-specific bitmap operations testing.

Key patterns include:

Mock objects for Resource and Transformation interfaces
Bitmap dimension verification
Resource recycling validation
Equality testing with hash verification

Technical Details

Testing infrastructure includes:

Robolectric test runner with SDK configuration
Mockito for mocking dependencies
BitmapPool implementation for resource management
KeyTester utility for equality testing
Custom test rules for consistent setup and teardown

Best Practices Demonstrated

The test suite exemplifies high-quality testing practices through organized and thorough validation approaches.

Proper test setup and cleanup with @Before and @After annotations
Comprehensive edge case coverage
Clear test method naming conventions
Efficient resource management validation
Regression testing implementation

bumptech/glide

library/test/src/test/java/com/bumptech/glide/load/resource/bitmap/CenterInsideTest.java

            
package com.bumptech.glide.load.resource.bitmap;

import static com.bumptech.glide.RobolectricConstants.ROBOLECTRIC_SDK;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotEquals;
import static org.mockito.ArgumentMatchers.any;
import static org.mockito.Mockito.doAnswer;
import static org.mockito.Mockito.never;
import static org.mockito.Mockito.verify;
import static org.mockito.Mockito.when;

import android.app.Application;
import android.graphics.Bitmap;
import androidx.test.core.app.ApplicationProvider;
import com.bumptech.glide.Glide;
import com.bumptech.glide.GlideBuilder;
import com.bumptech.glide.load.Transformation;
import com.bumptech.glide.load.engine.Resource;
import com.bumptech.glide.load.engine.bitmap_recycle.BitmapPool;
import com.bumptech.glide.load.engine.bitmap_recycle.BitmapPoolAdapter;
import com.bumptech.glide.tests.KeyTester;
import com.bumptech.glide.tests.Util;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import org.junit.After;
import org.junit.Before;
import org.junit.Rule;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.Mock;
import org.mockito.MockitoAnnotations;
import org.robolectric.RobolectricTestRunner;
import org.robolectric.annotation.Config;

@RunWith(RobolectricTestRunner.class)
@Config(sdk = ROBOLECTRIC_SDK)
public class CenterInsideTest {
  @Rule public final KeyTester keyTester = new KeyTester();

  @Mock private Resource<Bitmap> resource;
  @Mock private Transformation<Bitmap> transformation;
  private CenterInside centerInside;
  private int bitmapWidth;
  private int bitmapHeight;
  private Application context;

  @Before
  public void setUp() {
    MockitoAnnotations.initMocks(this);
    bitmapWidth = 100;
    bitmapHeight = 100;
    Bitmap bitmap = Bitmap.createBitmap(bitmapWidth, bitmapHeight, Bitmap.Config.ARGB_8888);
    when(resource.get()).thenReturn(bitmap);

    context = ApplicationProvider.getApplicationContext();
    BitmapPool pool = new BitmapPoolAdapter();
    Glide.init(context, new GlideBuilder().setBitmapPool(pool));

    centerInside = new CenterInside();
  }

  @After
  public void tearDown() {
    Glide.tearDown();
  }

  @Test
  public void testReturnsGivenResourceIfMatchesSizeExactly() {
    Resource<Bitmap> result = centerInside.transform(context, resource, bitmapWidth, bitmapHeight);

    assertEquals(resource, result);
  }

  @Test
  public void testReturnsGivenResourceIfSmallerThanTarget() {
    Resource<Bitmap> result = centerInside.transform(context, resource, 150, 150);

    assertEquals(resource, result);
  }

  @Test
  public void testReturnsNewResourceIfLargerThanTarget() {
    Resource<Bitmap> result = centerInside.transform(context, resource, 50, 50);

    assertNotEquals(resource, result);
  }

  @Test
  public void testDoesNotRecycleGivenResourceIfMatchesSizeExactly() {
    centerInside.transform(context, resource, bitmapWidth, bitmapHeight);

    verify(resource, never()).recycle();
  }

  @Test
  public void testDoesNotRecycleGivenResource() {
    centerInside.transform(context, resource, 50, 50);

    verify(resource, never()).recycle();
  }

  @Test
  public void testEquals() throws NoSuchAlgorithmException {
    doAnswer(new Util.WriteDigest("other"))
        .when(transformation)
        .updateDiskCacheKey(any(MessageDigest.class));

    keyTester
        .addEquivalenceGroup(new CenterInside(), new CenterInside(), centerInside)
        .addEquivalenceGroup(transformation)
        .addRegressionTest(
            new CenterInside(), "acf83850a2e8e9e809c8bfb999e2aede9e932cb897a15367fac9856b96f3ba33")
        .test();
  }
}