Back to Repositories
Testing R Class Resource Binding Implementation in ButterKnife

This test suite validates the R class functionality in ButterKnife, focusing on resource binding and code generation. It ensures proper handling of both final and non-final R classes, R2 class support, and correct generation of view binding code across different package scenarios.
Test Coverage Overview

The test suite provides comprehensive coverage of R class handling in ButterKnife:
Library resource binding with R2 class support
Application resource binding with final R class
Cross-package resource resolution (issue #779)
Compiled R class handling for Android framework resources
Implementation Analysis

The testing approach uses Google’s compile-testing framework to verify code generation. It employs JavaFileObjects to create mock source files and validates the generated binding code against expected outputs. The tests specifically verify correct resource ID resolution and binding class generation across different package scenarios.
Technical Details

Testing tools and configuration:
JUnit test framework
Google compile-testing library
ButterKnifeProcessor for annotation processing
Mock R and R2 class definitions
Compiler options for processing validation
Best Practices Demonstrated

The test suite demonstrates several testing best practices:
Comprehensive mock object creation for resource classes
Explicit verification of generated code structure
Edge case handling for cross-package scenarios
Clear separation of test cases for library vs application usage
jakewharton/butterknife

butterknife-runtime/src/test/java/butterknife/RClassTest.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.JavaSourcesSubjectFactory.javaSources;
import static java.util.Arrays.asList;

public class RClassTest {

  private static final JavaFileObject NON_FINAL_R = JavaFileObjects.forSourceString("test.R", ""
      + "package test;\n"
      + "public final class R {\n"
      + "  public static final class array {\n"
      + "    public static int res = 0x7f040001;\n"
      + "  }\n"
      + "  public static final class bool {\n"
      + "    public static int res = 0x7f040002;\n"
      + "  }\n"
      + "  public static final class color {\n"
      + "    public static int res = 0x7f040003;\n"
      + "  }\n"
      + "  public static final class integer {\n"
      + "    public static int res = 0x7f040004;\n"
      + "  }\n"
      + "  public static final class styleable {\n"
      + "    public static int[] ActionBar = { 0x7f010001, 0x7f010003 };\n"
      + "  }\n"
      + "}"
  );

  private static final JavaFileObject FINAL_R = JavaFileObjects.forSourceString("test.R", ""
      + "package test;\n"
      + "public final class R {\n"
      + "  public static final class array {\n"
      + "    public static final int res = 0x7f040001;\n"
      + "  }\n"
      + "  public static final class bool {\n"
      + "    public static final int res = 0x7f040002;\n"
      + "  }\n"
      + "  public static final class color {\n"
      + "    public static final int res = 0x7f040003;\n"
      + "  }\n"
      + "  public static final class integer {\n"
      + "    public static final int res = 0x7f040004;\n"
      + "  }\n"
      + "  public static final class string {\n"
      + "    public static final int res = 0x7f040005;\n"
      + "  }\n"
      + "  public static final class styleable {\n"
      + "    public static final int[] ActionBar = { 0x7f010001, 0x7f010003 };\n"
      + "  }\n"
      + "}"
  );

  private static final JavaFileObject R2 = JavaFileObjects.forSourceString("test.R2", ""
      + "package test;\n"
      + "public final class R2 {\n"
      + "  public static final class array {\n"
      + "    public static final int res = 0x7f040001;\n"
      + "  }\n"
      + "  public static final class bool {\n"
      + "    public static final int res = 0x7f040002;\n"
      + "  }\n"
      + "  public static final class color {\n"
      + "    public static final int res = 0x7f040003;\n"
      + "  }\n"
      + "  public static final class integer {\n"
      + "    public static final int res = 0x7f040004;\n"
      + "  }\n"
      + "  public static final class string {\n"
      + "    public static final int res = 0x7f040005;\n"
      + "  }\n"
      + "}"
  );

  @Test public void library() {
    JavaFileObject source = JavaFileObjects.forSourceString("test.Test", ""
        + "package test;\n"
        + "import butterknife.BindInt;\n"
        + "public class Test {\n"
        + "  @BindInt(R2.integer.res) int one;\n"
        + "}"
    );

    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"
        + "public class Test_ViewBinding implements Unbinder {\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"
        + "  public Test_ViewBinding(Test target, Context context) {\n"
        + "    Resources res = context.getResources();\n"
        + "    target.one = res.getInteger(R.integer.res);\n"
        + "  }\n"
        + "  @Override\n"
        + "  @CallSuper\n"
        + "  public void unbind() {\n"
        + "  }\n"
        + "}"
    );

    assertAbout(javaSources()).that(asList(source, NON_FINAL_R, R2))
        .withCompilerOptions("-Xlint:-processing")
        .processedWith(new ButterKnifeProcessor())
        .compilesWithoutWarnings()
        .and()
        .generatesSources(bindingSource);
  }

  @Test public void issue779() {
    JavaFileObject r2Bar = JavaFileObjects.forSourceString("test.bar.R2", ""
        + "package test.bar;\n"
        + "public final class R2 {\n"
        + "  public static final class array {\n"
        + "    public static final int res = 0x7f040001;\n"
        + "  }\n"
        + "  public static final class bool {\n"
        + "    public static final int res = 0x7f040002;\n"
        + "  }\n"
        + "  public static final class color {\n"
        + "    public static final int res = 0x7f040003;\n"
        + "  }\n"
        + "  public static final class id {\n"
        + "    public static final int res = 0x7f040004;\n"
        + "  }\n"
        + "  public static final class string {\n"
        + "    public static final int res = 0x7f040005;\n"
        + "  }\n"
        + "}");

    JavaFileObject nonFinalRBar = JavaFileObjects.forSourceString("test.bar.R", ""
        + "package test.bar;\n"
        + "public final class R {\n"
        + "  public static final class array {\n"
        + "    public static int res = 0x7f040001;\n"
        + "  }\n"
        + "  public static final class bool {\n"
        + "    public static int res = 0x7f040002;\n"
        + "  }\n"
        + "  public static final class color {\n"
        + "    public static int res = 0x7f040003;\n"
        + "  }\n"
        + "  public static final class id {\n"
        + "    public static int res = 0x7f040004;\n"
        + "  }\n"
        + "  public static final class styleable {\n"
        + "    public static int[] ActionBar = { 0x7f010001, 0x7f010003 };\n"
        + "  }\n"
        + "}"
    );

    JavaFileObject nonFinalRFoo = JavaFileObjects.forSourceString("test.foo.R", ""
        + "package test.foo;\n"
        + "public final class R {\n"
        + "  public static final class array {\n"
        + "    public static int res = 0x7f040001;\n"
        + "  }\n"
        + "  public static final class bool {\n"
        + "    public static int res = 0x7f040002;\n"
        + "  }\n"
        + "  public static final class color {\n"
        + "    public static int res = 0x7f040003;\n"
        + "  }\n"
        + "  public static final class id {\n"
        + "    public static int bogus = 0x7f040004;\n"
        + "  }\n"
        + "  public static final class styleable {\n"
        + "    public static int[] ActionBar = { 0x7f010001, 0x7f010003 };\n"
        + "  }\n"
        + "}"
    );

    JavaFileObject r2Foo = JavaFileObjects.forSourceString("test.foo.R2", ""
        + "package test.foo;\n"
        + "public final class R2 {\n"
        + "  public static final class array {\n"
        + "    public static final int res = 0x7f040001;\n"
        + "  }\n"
        + "  public static final class bool {\n"
        + "    public static final int res = 0x7f040002;\n"
        + "  }\n"
        + "  public static final class color {\n"
        + "    public static final int res = 0x7f040003;\n"
        + "  }\n"
        + "  public static final class id {\n"
        + "    public static final int bogus = 0x7f040004;\n"
        + "  }\n"
        + "  public static final class string {\n"
        + "    public static final int res = 0x7f040005;\n"
        + "  }\n"
        + "}");

    JavaFileObject fooSource = JavaFileObjects.forSourceString("test.foo.FooTest", ""
        + "package test.foo;\n"
        + "import android.app.Activity;\n"
        + "import android.view.View;\n"
        + "import butterknife.BindView;\n"
        + "public class FooTest extends Activity {\n"
        + "  @BindView(R2.id.bogus) View one;\n"
        + "}"
    );

    JavaFileObject barSource = JavaFileObjects.forSourceString("test.bar.Test", ""
        + "package test.bar;\n"
        + "import android.app.Activity;\n"
        + "import butterknife.BindView;\n"
        + "public class Test extends Activity {\n"
        + "  @BindView(R2.id.res) CustomView one;\n"
        + "}"
    );

    JavaFileObject customView = JavaFileObjects.forSourceString("test.bar.CustomView", ""
        + "package test.bar;\n"
        + "import android.view.View;\n"
        + "import android.content.Context;\n"
        + "public class CustomView extends View {\n"
        + "  public CustomView(Context context) {\n"
        + "    super(context);"
        + "  }"
        + "}"
    );

    JavaFileObject bindingSourceBar = JavaFileObjects.forSourceString("test/Test_ViewBinding", ""
        + "// Generated code from Butter Knife. Do not modify!\n"
        + "package test.bar;\n\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\n"
        + "public class Test_ViewBinding implements Unbinder {\n"
        + "  private Test target;\n\n"
        + "  @UiThread\n"
        + "  public Test_ViewBinding(Test target) {\n"
        + "    this(target, target.getWindow().getDecorView());\n"
        + "  }\n\n"
        + "  @UiThread\n"
        + "  public Test_ViewBinding(Test target, View source) {\n"
        + "    this.target = target;\n"
        + "    target.one = Utils.findRequiredViewAsType(source, R.id.res, \"field 'one'\", " +
        "CustomView.class);\n"
        + "  }\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\n"
        + "    target.one = null;\n\n"
        + "  }\n"
        + "}"
    );

    JavaFileObject bindingSourceFoo = JavaFileObjects.forSourceString("test/FooTest_ViewBinding", ""
        + "// Generated code from Butter Knife. Do not modify!\n"
        + "package test.foo;\n\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 FooTest_ViewBinding implements Unbinder {\n"
        + "  private FooTest target;\n\n"
        + "  @UiThread\n"
        + "  public FooTest_ViewBinding(FooTest target) {\n"
        + "    this(target, target.getWindow().getDecorView());\n"
        + "  }\n\n"
        + "  @UiThread\n"
        + "  public Test_ViewBinding(FooTest target, View source) {\n"
        + "    this.target = target;\n"
        + "    target.one = Utils.findRequiredView(source, R.id.bogus, \"field 'one'\");\n"
        + "  }\n"
        + "  @Override\n"
        + "  @CallSuper\n"
        + "  public void unbind() {\n"
        + "    FooTest target = this.target;\n"
        +
        "    if (target == null) throw new IllegalStateException(\"Bindings already cleared.\");\n\n"
        + "    this.target = null;\n\n"
        + "    target.one = null;\n\n"
        + "  }\n"
        + "}"
    );

    assertAbout(javaSources())
        .that(asList(customView, fooSource, barSource, nonFinalRBar, nonFinalRFoo, r2Bar, r2Foo))
        .withCompilerOptions("-Xlint:-processing")
        .processedWith(new ButterKnifeProcessor())
        .compilesWithoutWarnings()
        .and()
        .generatesSources(bindingSourceBar);

    assertAbout(javaSources())
        .that(asList(customView, fooSource, barSource, nonFinalRBar, nonFinalRFoo, r2Bar, r2Foo))
        .withCompilerOptions("-Xlint:-processing")
        .processedWith(new ButterKnifeProcessor())
        .compilesWithoutWarnings()
        .and()
        .generatesSources(bindingSourceFoo);
  }

  @Test public void app() {
    JavaFileObject source = JavaFileObjects.forSourceString("test.Test", ""
        + "package test;\n"
        + "import butterknife.BindBool;\n"
        + "public class Test {\n"
        + "  @BindBool(R.bool.res) boolean bool;\n"
        + "}"
    );

    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"
        + "public class Test_ViewBinding implements Unbinder {\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"
        + "  public Test_ViewBinding(Test target, Context context) {\n"
        + "    Resources res = context.getResources();\n"
        + "    target.bool = res.getBoolean(R.bool.res);\n"
        + "  }\n"
        + "  @Override\n"
        + "  @CallSuper\n"
        + "  public void unbind() {\n"
        + "  }\n"
        + "}"
    );

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

  @Test public void compiledRClass() {
    JavaFileObject source = JavaFileObjects.forSourceString("test.Test", ""
        + "package test;\n"
        + "import butterknife.BindColor;\n"
        + "public class Test {\n"
        + "  @BindColor(android.R.color.black) int black;\n"
        + "}"
    );

    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.view.View;\n"
        + "import androidx.annotation.CallSuper;\n"
        + "import androidx.annotation.UiThread;\n"
        + "import androidx.core.content.ContextCompat;\n"
        + "import butterknife.Unbinder;\n"
        + "import java.lang.Deprecated;\n"
        + "import java.lang.Override;\n"
        + "public class Test_ViewBinding implements Unbinder {\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"
        + "  public Test_ViewBinding(Test target, Context context) {\n"
        + "    target.black = ContextCompat.getColor(context, android.R.color.black);\n"
        + "  }\n"
        + "  @Override\n"
        + "  @CallSuper\n"
        + "  public void unbind() {\n"
        + "  }\n"
        + "}"
    );

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