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Validating View Extension Bindings in ButterKnife

This test suite validates the view extension capabilities in ButterKnife’s view binding functionality, focusing on resource binding and view field injection scenarios. The tests verify both basic resource binding and view field injection mechanisms in extended View classes.

Test Coverage Overview

The test suite provides comprehensive coverage of ButterKnife’s view extension functionality:

Resource binding validation using @BindBool annotation
View field injection testing with @BindView annotation
Generated binding class verification
Unbinding functionality verification

Implementation Analysis

The testing approach utilizes JUnit framework with Google’s compile-testing library to validate code generation. It employs source code comparison to verify the correct generation of binding classes, ensuring proper implementation of view binding and unbinding mechanisms.

The tests specifically focus on compile-time code generation and annotation processing verification.

Technical Details

Testing tools and configuration:

JUnit test framework
Google’s compile-testing library for source validation
ButterKnifeProcessor for annotation processing
JavaFileObjects for source code representation
Custom compiler options (-Xlint:-processing)

Best Practices Demonstrated

The test suite exemplifies several testing best practices:

Isolated test cases for different binding scenarios
Thorough verification of generated code
Proper error handling validation
Clear test method naming conventions
Comprehensive assertion checks for compilation results

jakewharton/butterknife

butterknife-runtime/src/test/java/butterknife/ExtendViewTest.java

            
package butterknife;

import butterknife.compiler.ButterKnifeProcessor;
import com.google.testing.compile.JavaFileObjects;
import javax.tools.JavaFileObject;
import org.junit.Test;

import static com.google.common.truth.Truth.assertAbout;
import static com.google.testing.compile.JavaSourceSubjectFactory.javaSource;

public class ExtendViewTest {
  @Test public void onlyResources() {
    JavaFileObject source = JavaFileObjects.forSourceString("test.Test", ""
        + "package test;"
        + "import android.content.Context;"
        + "import android.view.View;"
        + "import butterknife.BindBool;"
        + "public class Test extends View {"
        + "  Test(Context context) {"
        + "    super(context);"
        + "  }"
        + "  @BindBool(1) boolean one;"
        + "}"
    );

    JavaFileObject bindingSource = JavaFileObjects.forSourceString("test/Test_ViewBinding", ""
        + "// Generated code from Butter Knife. Do not modify!\n"
        + "package test;\n"
        + "import android.content.Context;\n"
        + "import android.content.res.Resources;\n"
        + "import android.view.View;\n"
        + "import androidx.annotation.CallSuper;\n"
        + "import androidx.annotation.UiThread;\n"
        + "import butterknife.Unbinder;\n"
        + "import java.lang.Deprecated;\n"
        + "import java.lang.Override;\n"
        + "import java.lang.SuppressWarnings;\n"
        + "public class Test_ViewBinding implements Unbinder {\n"
        + "  @UiThread\n"
        + "  public Test_ViewBinding(Test target) {\n"
        + "    this(target, target.getContext());\n"
        + "  }\n"
        + "  /**\n"
        + "   * @deprecated Use {@link #Test_ViewBinding(Test, Context)} for direct creation.\n"
        + "   *     Only present for runtime invocation through {@code ButterKnife.bind()}.\n"
        + "   */\n"
        + "  @Deprecated\n"
        + "  @UiThread\n"
        + "  public Test_ViewBinding(Test target, View source) {\n"
        + "    this(target, source.getContext());\n"
        + "  }\n"
        + "  @UiThread\n"
        + "  @SuppressWarnings(\"ResourceType\")\n"
        + "  public Test_ViewBinding(Test target, Context context) {\n"
        + "    Resources res = context.getResources();\n"
        + "    target.one = res.getBoolean(1);\n"
        + "  }\n"
        + "  @Override\n"
        + "  @CallSuper\n"
        + "  public void unbind() {\n"
        + "  }\n"
        + "}"
    );

    assertAbout(javaSource()).that(source)
        .withCompilerOptions("-Xlint:-processing")
        .processedWith(new ButterKnifeProcessor())
        .compilesWithoutWarnings()
        .and()
        .generatesSources(bindingSource);
  }

  @Test public void views() {
    JavaFileObject source = JavaFileObjects.forSourceString("test.Test", ""
        + "package test;"
        + "import android.content.Context;"
        + "import android.view.View;"
        + "import butterknife.BindView;"
        + "public class Test extends View {"
        + "  Test(Context context) {"
        + "    super(context);"
        + "  }"
        + "  @BindView(1) View one;"
        + "}"
    );

    JavaFileObject bindingSource = JavaFileObjects.forSourceString("test/Test_ViewBinding", ""
        + "package test;\n"
        + "import android.view.View;\n"
        + "import androidx.annotation.CallSuper;\n"
        + "import androidx.annotation.UiThread;\n"
        + "import butterknife.Unbinder;\n"
        + "import butterknife.internal.Utils;\n"
        + "import java.lang.IllegalStateException;\n"
        + "import java.lang.Override;\n"
        + "public class Test_ViewBinding implements Unbinder {\n"
        + "  private Test target;\n"
        + "  @UiThread\n"
        + "  public Test_ViewBinding(Test target) {\n"
        + "    this(target, target);\n"
        + "  }\n"
        + "  @UiThread\n"
        + "  public Test_ViewBinding(Test target, View source) {\n"
        + "    this.target = target;\n"
        + "    target.one = Utils.findRequiredView(source, 1, \"field 'one'\");\n"
        + "  }\n"
        + "  @Override\n"
        + "  @CallSuper\n"
        + "  public void unbind() {\n"
        + "    Test target = this.target;\n"
        + "    if (target == null) throw new IllegalStateException(\"Bindings already cleared.\");\n"
        + "    this.target = null;\n"
        + "    target.one = null;\n"
        + "  }\n"
        + "}"
    );

    assertAbout(javaSource()).that(source)
        .withCompilerOptions("-Xlint:-processing")
        .processedWith(new ButterKnifeProcessor())
        .compilesWithoutWarnings()
        .and()
        .generatesSources(bindingSource);
  }
}