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Validating Drawable Resource Binding Implementation in ButterKnife

This test suite validates the BindDrawable annotation functionality in ButterKnife, ensuring proper binding and unbinding of drawable resources to fields. It verifies the correct handling of Android drawable resources through ButterKnife’s dependency injection mechanism.

Test Coverage Overview

The test coverage focuses on the @BindDrawable annotation functionality, verifying resource binding and state preservation.

Tests drawable resource injection into annotated fields
Validates constant state equality between bound and expected drawables
Verifies state persistence after unbinding
Ensures proper integration with Android’s resource system

Implementation Analysis

The testing approach employs JUnit with Android Instrumentation testing to validate drawable resource binding.

Key implementation patterns include:

Using InstrumentationRegistry for context access
Implementing target class with @BindDrawable annotation
Comparing drawable constant states for equality verification
Testing both binding and unbinding lifecycle events

Technical Details

Testing infrastructure includes:

JUnit test framework
Android Instrumentation Testing
ButterKnife annotation processing
Google Truth assertion library
Custom ViewTree test utility
Android resource management system

Best Practices Demonstrated

The test exhibits several testing best practices for Android resource management.

Proper resource cleanup through unbinder usage
Isolated test context management
Effective state comparison techniques
Clear test method naming and organization
Resource binding lifecycle verification

jakewharton/butterknife

butterknife-integration-test/src/androidTest/java/com/example/butterknife/functional/BindDrawableTest.java

            
package com.example.butterknife.functional;

import android.content.Context;
import android.graphics.drawable.Drawable;
import android.view.View;
import androidx.test.InstrumentationRegistry;
import butterknife.BindDrawable;
import butterknife.ButterKnife;
import butterknife.Unbinder;
import com.example.butterknife.test.R;
import org.junit.Test;

import static com.google.common.truth.Truth.assertThat;

public final class BindDrawableTest {
  private final Context context = InstrumentationRegistry.getContext();
  private final View tree = ViewTree.create(1);

  static class Target {
    @BindDrawable(R.drawable.circle) Drawable actual;
  }

  @Test public void asDrawable() {
    Target target = new Target();
    Drawable expected = context.getResources().getDrawable(R.drawable.circle);

    Unbinder unbinder = ButterKnife.bind(target, tree);
    assertThat(target.actual.getConstantState()).isEqualTo(expected.getConstantState());

    unbinder.unbind();
    assertThat(target.actual.getConstantState()).isEqualTo(expected.getConstantState());
  }
}