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Testing View Binding Unbinder Implementation in ButterKnife

This test suite validates the ButterKnife view binding unbinding functionality across inheritance hierarchies and multiple view bindings. It ensures proper cleanup of view references and event listeners when unbinding views in Android applications.
Test Coverage Overview

The test suite covers multiple binding scenarios including:
Multiple view and event bindings in a single class
Inheritance chains with view bindings at different levels
Complex hierarchies with mixed binding types (views, colors, click listeners)
Edge cases around unbinding and cleanup
Implementation Analysis

The testing approach uses compile-time verification through the ButterKnifeProcessor to validate generated binding code. It leverages JavaFileObjects for source definition and compilation testing, with detailed verification of the generated binding implementations including proper cleanup in unbind() methods.
Technical Details

Testing tools and configuration:
JUnit test framework
Google Truth assertion library
JavaFileObjects for source compilation
ButterKnifeProcessor annotation processor
Compiler options for processing validation
Best Practices Demonstrated

The test suite demonstrates high-quality testing practices including:
Comprehensive coverage of inheritance scenarios
Validation of generated code structure and content
Proper cleanup verification
Edge case handling for binding states
Clear test organization and naming
jakewharton/butterknife

butterknife-runtime/src/test/java/butterknife/UnbinderTest.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;
import static com.google.testing.compile.JavaSourcesSubjectFactory.javaSources;
import static java.util.Arrays.asList;

public class UnbinderTest {
  @Test public void multipleBindings() {
    JavaFileObject source = JavaFileObjects.forSourceString("test.Test", ""
        + "package test;\n"
        + "import android.view.View;\n"
        + "import butterknife.BindView;\n"
        + "import butterknife.OnClick;\n"
        + "import butterknife.OnLongClick;\n"
        + "public class Test {\n"
        + "  @BindView(1) View view;\n"
        + "  @BindView(2) View view2;\n"
        + "  @OnClick(1) void doStuff() {}\n"
        + "  @OnLongClick(1) boolean doMoreStuff() { return false; }\n"
        + "}"
    );

    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.DebouncingOnClickListener;\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"
        + "  private View view1;\n"
        + "  @UiThread\n"
        + "  public Test_ViewBinding(final Test target, View source) {\n"
        + "    this.target = target;\n"
        + "    View view;\n"
        + "    view = Utils.findRequiredView(source, 1, \"field 'view', method 'doStuff', and method 'doMoreStuff'\");\n"
        + "    target.view = view;\n"
        + "    view1 = view;\n"
        + "    view.setOnClickListener(new DebouncingOnClickListener() {\n"
        + "      @Override\n"
        + "      public void doClick(View p0) {\n"
        + "        target.doStuff();\n"
        + "      }\n"
        + "    });\n"
        + "    view.setOnLongClickListener(new View.OnLongClickListener() {\n"
        + "      @Override\n"
        + "      public boolean onLongClick(View p0) {\n"
        + "        return target.doMoreStuff();\n"
        + "      }\n"
        + "    });\n"
        + "    target.view2 = Utils.findRequiredView(source, 2, \"field 'view2'\");\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.view = null;\n"
        + "    target.view2 = null;\n"
        + "    view1.setOnClickListener(null);\n"
        + "    view1.setOnLongClickListener(null);\n"
        + "    view1 = null;\n"
        + "  }\n"
        + "}"
    );

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

  @Test public void unbindingThroughAbstractChild() {
    JavaFileObject source1 = JavaFileObjects.forSourceString("test.Test", ""
        + "package test;\n"
        + "import butterknife.OnClick;\n"
        + "public class Test {\n"
        + "  @OnClick(1) void doStuff1() { }\n"
        + "}"
    );

    JavaFileObject source2 = JavaFileObjects.forSourceString("test.TestOne", ""
        + "package test;\n"
        + "public abstract class TestOne extends Test {\n"
        + "}"
    );

    JavaFileObject source3 = JavaFileObjects.forSourceString("test.TestTwo", ""
        + "package test;\n"
        + "import butterknife.OnClick;\n"
        + "class TestTwo extends TestOne {\n"
        + "  @OnClick(1) void doStuff2() { }\n"
        + "}"
    );

    JavaFileObject binding1Source = 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.DebouncingOnClickListener;\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"
        + "  private View view1;\n"
        + "  @UiThread\n"
        + "  public Test_ViewBinding(final Test target, View source) {\n"
        + "    this.target = target;\n"
        + "    View view;\n"
        + "    view = Utils.findRequiredView(source, 1, \"method 'doStuff1'\");\n"
        + "    view1 = view;\n"
        + "    view.setOnClickListener(new DebouncingOnClickListener() {\n"
        + "      @Override\n"
        + "      public void doClick(View p0) {\n"
        + "        target.doStuff1();\n"
        + "      }\n"
        + "    });\n"
        + "  }\n"
        + "  @Override\n"
        + "  @CallSuper\n"
        + "  public void unbind() {\n"
        + "    if (target == null) throw new IllegalStateException(\"Bindings already cleared.\");\n"
        + "    target = null;\n"
        + "    view1.setOnClickListener(null);\n"
        + "    view1 = null;\n"
        + "  }\n"
        + "}"
    );

    JavaFileObject binding2Source = JavaFileObjects.forSourceString("test/TestTwo_ViewBinding", ""
        + "package test;\n"
        + "import android.view.View;\n"
        + "import androidx.annotation.UiThread;\n"
        + "import butterknife.internal.DebouncingOnClickListener;\n"
        + "import butterknife.internal.Utils;\n"
        + "import java.lang.IllegalStateException;\n"
        + "import java.lang.Override;\n"
        + "public class TestTwo_ViewBinding extends Test_ViewBinding {\n"
        + "  private TestTwo target;\n"
        + "  private View view1;\n"
        + "  @UiThread\n"
        + "  public TestTwo_ViewBinding(final TestTwo target, View source) {\n"
        + "    super(target, source);\n"
        + "    this.target = target;\n"
        + "    View view;\n"
        + "    view = Utils.findRequiredView(source, 1, \"method 'doStuff2'\");\n"
        + "    view1 = view;\n"
        + "    view.setOnClickListener(new DebouncingOnClickListener() {\n"
        + "      @Override\n"
        + "      public void doClick(View p0) {\n"
        + "        target.doStuff2();\n"
        + "      }\n"
        + "    });\n"
        + "  }\n"
        + "  @Override\n"
        + "  public void unbind() {\n"
        + "    if (target == null) throw new IllegalStateException(\"Bindings already cleared.\");\n"
        + "    target = null;\n"
        + "    view1.setOnClickListener(null);\n"
        + "    view1 = null;\n"
        + "    super.unbind();\n"
        + "  }\n"
        + "}"
    );

    assertAbout(javaSources()).that(asList(source1, source2, source3))
        .withCompilerOptions("-Xlint:-processing")
        .processedWith(new ButterKnifeProcessor())
        .compilesWithoutWarnings()
        .and()
        .generatesSources(binding1Source, binding2Source);
  }

  @Test public void fullIntegration() {
    JavaFileObject sourceA = JavaFileObjects.forSourceString("test.A", ""
        + "package test;\n"
        + "import android.view.View;\n"
        + "import androidx.annotation.ColorInt;\n"
        + "import butterknife.BindColor;\n"
        + "public class A {\n"
        + "  @BindColor(android.R.color.black) @ColorInt int blackColor;\n"
        + "  public A(View view) {\n"
        + "  }\n"
        + "}\n");

    JavaFileObject sourceB = JavaFileObjects.forSourceString("test.B", ""
        + "package test;\n"
        + "import android.view.View;\n"
        + "import androidx.annotation.ColorInt;\n"
        + "import butterknife.BindColor;\n"
        + "public class B extends A {\n"
        + "  @BindColor(android.R.color.white) @ColorInt int whiteColor;\n"
        + "  public B(View view) {\n"
        + "    super(view);\n"
        + "  }\n"
        + "}\n");

    JavaFileObject sourceC = JavaFileObjects.forSourceString("test.C", ""
        + "package test;\n"
        + "import android.view.View;\n"
        + "import androidx.annotation.ColorInt;\n"
        + "import butterknife.BindView;\n"
        + "import butterknife.BindColor;\n"
        + "public class C extends B {\n"
        + "  @BindColor(android.R.color.transparent) @ColorInt int transparentColor;\n"
        + "  @BindView(android.R.id.button1) View button1;\n"
        + "  public C(View view) {\n"
        + "    super(view);\n"
        + "  }\n"
        + "}\n");

    JavaFileObject sourceD = JavaFileObjects.forSourceString("test.D", ""
        + "package test;\n"
        + "import android.view.View;\n"
        + "import androidx.annotation.ColorInt;\n"
        + "import butterknife.BindColor;\n"
        + "public class D extends C {\n"
        + "  @BindColor(android.R.color.darker_gray) @ColorInt int grayColor;\n"
        + "  public D(View view) {\n"
        + "    super(view);\n"
        + "  }\n"
        + "}\n");

    JavaFileObject sourceE = JavaFileObjects.forSourceString("test.E", ""
        + "package test;\n"
        + "import android.view.View;\n"
        + "import androidx.annotation.ColorInt;\n"
        + "import butterknife.BindColor;\n"
        + "public class E extends C {\n"
        + "  @BindColor(android.R.color.background_dark) @ColorInt int backgroundDarkColor;\n"
        + "  public E(View view) {\n"
        + "    super(view);\n"
        + "  }\n"
        + "}\n");

    JavaFileObject sourceF = JavaFileObjects.forSourceString("test.F", ""
        + "package test;\n"
        + "import android.view.View;\n"
        + "import androidx.annotation.ColorInt;\n"
        + "import butterknife.BindColor;\n"
        + "public class F extends D {\n"
        + "  @BindColor(android.R.color.background_light) @ColorInt int backgroundLightColor;\n"
        + "  public F(View view) {\n"
        + "    super(view);\n"
        + "  }\n"
        + "}\n");

    JavaFileObject sourceG = JavaFileObjects.forSourceString("test.G", ""
        + "package test;\n"
        + "import android.view.View;\n"
        + "import androidx.annotation.ColorInt;\n"
        + "import butterknife.BindView;\n"
        + "import butterknife.BindColor;\n"
        + "import butterknife.OnClick;\n"
        + "public class G extends E {\n"
        + "  @BindColor(android.R.color.darker_gray) @ColorInt int grayColor;\n"
        + "  @BindView(android.R.id.button2) View button2;\n"
        + "  public G(View view) {\n"
        + "    super(view);\n"
        + "  }\n"
        + "  @OnClick(android.R.id.content) public void onClick() {\n"
        + "  }\n"
        + "}\n");

    JavaFileObject sourceH = JavaFileObjects.forSourceString("test.H", ""
        + "package test;\n"
        + "import android.view.View;\n"
        + "import androidx.annotation.ColorInt;\n"
        + "import butterknife.BindView;\n"
        + "import butterknife.BindColor;\n"
        + "public class H extends G {\n"
        + "  @BindColor(android.R.color.holo_green_dark) @ColorInt int holoGreenDark;\n"
        + "  @BindView(android.R.id.button3) View button3;\n"
        + "  public H(View view) {\n"
        + "    super(view);\n"
        + "  }\n"
        + "}\n");

    JavaFileObject bindingASource = JavaFileObjects.forSourceString("test/A_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 A_ViewBinding implements Unbinder {\n"
        + "  /**\n"
        + "   * @deprecated Use {@link #Test_ViewBinding(A, Context)} for direct creation.\n"
        + "   *     Only present for runtime invocation through {@code ButterKnife.bind()}.\n"
        + "   */\n"
        + "  @Deprecated\n"
        + "  @UiThread\n"
        + "  public Test_ViewBinding(A target, View source) {\n"
        + "    this(target, source.getContext());\n"
        + "  }\n"
        + "  @UiThread\n"
        + "  public A_ViewBinding(A target, Context context) {\n"
        + "    target.blackColor = ContextCompat.getColor(context, android.R.color.black);\n"
        + "  }\n"
        + "  @Override\n"
        + "  @CallSuper\n"
        + "  public void unbind() {\n"
        + "  }\n"
        + "}"
    );

    JavaFileObject bindingBSource = JavaFileObjects.forSourceString("test/B_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.UiThread;\n"
        + "import androidx.core.content.ContextCompat;\n"
        + "import java.lang.Deprecated;\n"
        + "public class B_ViewBinding extends A_ViewBinding {\n"
        + "  /**\n"
        + "   * @deprecated Use {@link #Test_ViewBinding(B, Context)} for direct creation.\n"
        + "   *     Only present for runtime invocation through {@code ButterKnife.bind()}.\n"
        + "   */\n"
        + "  @Deprecated\n"
        + "  @UiThread\n"
        + "  public Test_ViewBinding(B target, View source) {\n"
        + "    this(target, source.getContext());\n"
        + "  }\n"
        + "  @UiThread\n"
        + "  public B_ViewBinding(B target, Context context) {\n"
        + "    super(target, context);\n"
        + "    target.whiteColor = ContextCompat.getColor(context, android.R.color.white);\n"
        + "  }\n"
        + "}"
    );

    JavaFileObject bindingCSource = JavaFileObjects.forSourceString("test/C_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.UiThread;\n"
        + "import androidx.core.content.ContextCompat;\n"
        + "import butterknife.internal.Utils;\n"
        + "import java.lang.IllegalStateException;\n"
        + "import java.lang.Override;\n"
        + "public class C_ViewBinding extends B_ViewBinding {\n"
        + "  private C target;\n"
        + "  @UiThread\n"
        + "  public C_ViewBinding(C target, View source) {\n"
        + "    super(target, source.getContext());\n"
        + "    this.target = target;\n"
        + "    target.button1 = Utils.findRequiredView(source, android.R.id.button1, \"field 'button1'\");\n"
        + "    Context context = source.getContext();\n"
        + "    target.transparentColor = ContextCompat.getColor(context, android.R.color.transparent);\n"
        + "  }\n"
        + "  @Override\n"
        + "  public void unbind() {\n"
        + "    C target = this.target;\n"
        + "    if (target == null) throw new IllegalStateException(\"Bindings already cleared.\");\n"
        + "    this.target = null;\n"
        + "    target.button1 = null;\n"
        + "    super.unbind();\n"
        + "  }\n"
        + "}"
    );

    JavaFileObject bindingDSource = JavaFileObjects.forSourceString("test/D_ViewBinding", ""
        + "package test;\n"
        + "import android.content.Context;\n"
        + "import android.view.View;\n"
        + "import androidx.annotation.UiThread;\n"
        + "import androidx.core.content.ContextCompat;\n"
        + "public class D_ViewBinding extends C_ViewBinding {\n"
        + "  @UiThread\n"
        + "  public D_ViewBinding(D target, View source) {\n"
        + "    super(target, source);\n"
        + "    Context context = source.getContext();\n"
        + "    target.grayColor = ContextCompat.getColor(context, android.R.color.darker_gray);\n"
        + "  }\n"
        + "}"
    );

    JavaFileObject bindingESource = JavaFileObjects.forSourceString("test/E_ViewBinding", ""
        + "package test;\n"
        + "import android.content.Context;\n"
        + "import android.view.View;\n"
        + "import androidx.annotation.UiThread;\n"
        + "import androidx.core.content.ContextCompat;\n"
        + "public class E_ViewBinding extends C_ViewBinding {\n"
        + "  @UiThread\n"
        + "  public E_ViewBinding(E target, View source) {\n"
        + "    super(target, source);\n"
        + "    Context context = source.getContext();\n"
        + "    target.backgroundDarkColor = ContextCompat.getColor(context, android.R.color.background_dark);\n"
        + "  }\n"
        + "}"
    );

    JavaFileObject bindingFSource = JavaFileObjects.forSourceString("test/F_ViewBinding", ""
        + "package test;\n"
        + "import android.content.Context;\n"
        + "import android.view.View;\n"
        + "import androidx.annotation.UiThread;\n"
        + "import androidx.core.content.ContextCompat;\n"
        + "public class F_ViewBinding extends D_ViewBinding {\n"
        + "  @UiThread\n"
        + "  public F_ViewBinding(F target, View source) {\n"
        + "    super(target, source);\n"
        + "    Context context = source.getContext();\n"
        + "    target.backgroundLightColor = ContextCompat.getColor(context, android.R.color.background_light);\n"
        + "  }\n"
        + "}"
    );

    JavaFileObject bindingGSource = JavaFileObjects.forSourceString("test/G_ViewBinding", ""
        + "package test;\n"
        + "import android.content.Context;\n"
        + "import android.view.View;\n"
        + "import androidx.annotation.UiThread;\n"
        + "import androidx.core.content.ContextCompat;\n"
        + "import butterknife.internal.DebouncingOnClickListener;\n"
        + "import butterknife.internal.Utils;\n"
        + "import java.lang.IllegalStateException;\n"
        + "import java.lang.Override;\n"
        + "public class G_ViewBinding extends E_ViewBinding {\n"
        + "  private G target;\n"
        + "  private View view1020002;\n"
        + "  @UiThread\n"
        + "  public G_ViewBinding(final G target, View source) {\n"
        + "    super(target, source);\n"
        + "    this.target = target;\n"
        + "    View view;\n"
        + "    target.button2 = Utils.findRequiredView(source, android.R.id.button2, \"field 'button2'\");\n"
        + "    view = Utils.findRequiredView(source, android.R.id.content, \"method 'onClick'\");\n"
        + "    view1020002 = view;\n"
        + "    view.setOnClickListener(new DebouncingOnClickListener() {\n"
        + "      @Override\n"
        + "      public void doClick(View p0) {\n"
        + "        target.onClick();\n"
        + "      }\n"
        + "    });\n"
        + "    Context context = source.getContext();\n"
        + "    target.grayColor = ContextCompat.getColor(context, android.R.color.darker_gray);\n"
        + "  }\n"
        + "  @Override\n"
        + "  public void unbind() {\n"
        + "    G target = this.target;\n"
        + "    if (target == null) throw new IllegalStateException(\"Bindings already cleared.\");\n"
        + "    this.target = null\n"
        + "    target.button2 = null;\n"
        + "    view1020002.setOnClickListener(null);\n"
        + "    view1020002 = null;\n"
        + "    super.unbind();\n"
        + "  }\n"
        + "}"
    );

    JavaFileObject bindingHSource = JavaFileObjects.forSourceString("test/H_ViewBinding", ""
        + "package test;\n"
        + "import android.content.Context;\n"
        + "import android.view.View;\n"
        + "import androidx.annotation.UiThread;\n"
        + "import androidx.core.content.ContextCompat;\n"
        + "import butterknife.internal.Utils;\n"
        + "import java.lang.IllegalStateException;\n"
        + "import java.lang.Override;\n"
        + "public class H_ViewBinding extends G_ViewBinding {\n"
        + "  private H target;\n"
        + "  @UiThread\n"
        + "  public H_ViewBinding(H target, View source) {\n"
        + "    super(target, source);\n"
        + "    this.target = target;\n"
        + "    target.button3 = Utils.findRequiredView(source, android.R.id.button3, \"field 'button3'\");\n"
        + "    Context context = source.getContext();\n"
        + "    target.holoGreenDark = ContextCompat.getColor(context, android.R.color.holo_green_dark);\n"
        + "  }\n"
        + "  @Override\n"
        + "  public void unbind() {\n"
        + "    H target = this.target;\n"
        + "    if (target == null) throw new IllegalStateException(\"Bindings already cleared.\");\n"
        + "    this.target = null;\n"
        + "    target.button3 = null;\n"
        + "    super.unbind();\n"
        + "  }\n"
        + "}"
    );

    assertAbout(javaSources())
        .that(asList(
            sourceA,
            sourceB,
            sourceC,
            sourceD,
            sourceE,
            sourceF,
            sourceG,
            sourceH))
        .withCompilerOptions("-Xlint:-processing")
        .processedWith(new ButterKnifeProcessor())
        .compilesWithoutWarnings()
        .and()
        .generatesSources(
            bindingASource,
            bindingBSource,
            bindingCSource,
            bindingDSource,
            bindingESource,
            bindingFSource,
            bindingGSource,
            bindingHSource);
  }
}