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Testing Bitmap FitCenter Transformation Implementation in Bumptech Glide

This test suite validates the FitCenter transformation functionality in Glide, a popular Android image loading library. The tests ensure proper bitmap resizing behavior and resource management when applying the fit center transformation to images.

Test Coverage Overview

The test suite provides comprehensive coverage of the FitCenter transformation class, focusing on resource handling and size matching scenarios.

Tests exact size matching behavior for bitmap resources
Validates resource recycling policies
Verifies transformation equality and caching behavior
Covers edge cases in bitmap dimension handling

Implementation Analysis

The testing approach utilizes JUnit and Robolectric for Android-specific bitmap operations testing. The implementation employs Mockito for mocking dependencies and isolating the transformation logic.

Key patterns include:

Setup/teardown patterns for Glide initialization
Mock bitmap resource management
Equality testing with KeyTester utility

Technical Details

Testing infrastructure includes:

JUnit 4 test framework
Robolectric for Android SDK simulation
Mockito for mocking and verification
Custom KeyTester utility for equality testing
BitmapPool implementation for resource management

Best Practices Demonstrated

The test suite exemplifies several testing best practices in Android image processing context.

Proper test isolation through @Before/@After hooks
Comprehensive mock object initialization
Resource cleanup verification
Regression testing with hash verification
Clear test method naming conventions

bumptech/glide

library/test/src/test/java/com/bumptech/glide/load/resource/bitmap/FitCenterTest.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.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 FitCenterTest {
  @Rule public final KeyTester keyTester = new KeyTester();

  @Mock private Resource<Bitmap> resource;
  @Mock private Transformation<Bitmap> transformation;
  private FitCenter fitCenter;
  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);

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

    fitCenter = new FitCenter();
  }

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

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

    assertEquals(resource, result);
  }

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

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

  @Test
  public void testDoesNotRecycleGivenResource() {
    fitCenter.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(fitCenter, new FitCenter(), new FitCenter())
        .addEquivalenceGroup(transformation)
        .addRegressionTest(
            new FitCenter(), "eda03bc6969032145110add4bfe399915897406f4ca3a1a7512d07750e60f90d")
        .test();
  }
}