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Testing Local URI Stream Fetching Implementation in Glide

This test suite validates the StreamLocalUriFetcher component in Glide, focusing on handling local URI resources and input stream processing. It verifies proper stream loading behavior and error handling when accessing local files through ContentResolver.

Test Coverage Overview

The test suite provides comprehensive coverage of the StreamLocalUriFetcher class, focusing on local URI resource handling.

Key areas tested include:

Successful input stream retrieval from local URIs
Proper error handling for null input streams
Integration with Android’s ContentResolver
Callback behavior for both success and failure scenarios

Implementation Analysis

The testing approach utilizes Robolectric for Android environment simulation and Mockito for dependency mocking.

Key implementation patterns include:

Shadow classes for ContentResolver behavior simulation
Mock callbacks to verify asynchronous operations
Priority handling verification
URI parsing and resource access testing

Technical Details

Testing infrastructure includes:

JUnit 4 test framework
Robolectric test runner with SDK configuration
Mockito for mocking and verification
Custom ContentResolverShadow for resource simulation
ApplicationProvider for context access

Best Practices Demonstrated

The test suite exemplifies several testing best practices for Android components.

Notable practices include:

Proper test setup and initialization using @Before
Isolated test cases with specific assertions
Effective use of mocking for external dependencies
Clear separation of success and failure scenarios
Comprehensive error condition coverage

bumptech/glide

library/test/src/test/java/com/bumptech/glide/load/data/resource/StreamLocalUriFetcherTest.java

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

import static com.bumptech.glide.RobolectricConstants.ROBOLECTRIC_SDK;
import static org.mockito.ArgumentMatchers.isA;
import static org.mockito.Mockito.verify;

import android.content.ContentResolver;
import android.content.Context;
import android.net.Uri;
import androidx.test.core.app.ApplicationProvider;
import com.bumptech.glide.Priority;
import com.bumptech.glide.load.data.DataFetcher;
import com.bumptech.glide.load.data.StreamLocalUriFetcher;
import com.bumptech.glide.tests.ContentResolverShadow;
import java.io.ByteArrayInputStream;
import java.io.FileNotFoundException;
import java.io.InputStream;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.ArgumentMatchers;
import org.mockito.Mock;
import org.mockito.MockitoAnnotations;
import org.robolectric.RobolectricTestRunner;
import org.robolectric.annotation.Config;
import org.robolectric.shadow.api.Shadow;

@RunWith(RobolectricTestRunner.class)
@Config(
    sdk = ROBOLECTRIC_SDK,
    shadows = {ContentResolverShadow.class})
public class StreamLocalUriFetcherTest {
  @Mock private DataFetcher.DataCallback<InputStream> callback;

  @Before
  public void setUp() {
    MockitoAnnotations.initMocks(this);
  }

  @Test
  public void testLoadResource_returnsInputStream() throws Exception {
    Context context = ApplicationProvider.getApplicationContext();
    Uri uri = Uri.parse("file://nothing");

    ContentResolver contentResolver = context.getContentResolver();
    ContentResolverShadow shadow = Shadow.extract(contentResolver);
    shadow.registerInputStream(uri, new ByteArrayInputStream(new byte[0]));

    StreamLocalUriFetcher fetcher = new StreamLocalUriFetcher(context.getContentResolver(), uri);
    fetcher.loadData(Priority.NORMAL, callback);
    verify(callback).onDataReady(ArgumentMatchers.<InputStream>isNotNull());
  }

  @Test
  public void testLoadResource_withNullInputStream_callsLoadFailed() {
    Context context = ApplicationProvider.getApplicationContext();
    Uri uri = Uri.parse("file://nothing");

    ContentResolver contentResolver = context.getContentResolver();
    ContentResolverShadow shadow = Shadow.extract(contentResolver);

    shadow.registerInputStream(uri, null /*inputStream*/);

    StreamLocalUriFetcher fetcher = new StreamLocalUriFetcher(context.getContentResolver(), uri);
    fetcher.loadData(Priority.LOW, callback);

    verify(callback).onLoadFailed(isA(FileNotFoundException.class));
  }
}