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Testing OnItemSelected View Binding Implementation in ButterKnife

This test suite validates the OnItemSelected functionality in ButterKnife’s view binding system, focusing on item selection callback handling in Android AdapterViews. The tests verify both default and custom selection behaviors, along with multiple binding scenarios.

Test Coverage Overview

The test suite provides comprehensive coverage of OnItemSelected annotations and their runtime behavior.

Key areas tested include:

Default item selection method implementations
Custom nothing-selected callbacks
Multiple method bindings on single views
Complex binding permutations across multiple views

Implementation Analysis

The testing approach uses JUnit to verify ButterKnife’s code generation capabilities. Tests employ the JavaFileObjects utility to create source code representations and validate generated binding classes against expected implementations.

Technical patterns include:

Compile-time annotation processing verification
Generated source code validation
Binding lifecycle management testing

Technical Details

Testing tools and configuration:

JUnit test framework
Google Truth assertion library
JavaFileObjects for source code manipulation
ButterKnifeProcessor for annotation processing
Compiler options: -Xlint:-processing

Best Practices Demonstrated

The test suite exemplifies high-quality testing practices through thorough verification of generated code, explicit error handling, and comprehensive coverage of edge cases.

Notable practices include:

Systematic validation of generated binding code
Explicit testing of lifecycle methods
Comprehensive callback permutation testing
Clean separation of test cases

jakewharton/butterknife

butterknife-runtime/src/test/java/butterknife/OnItemSelectedTest.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;

/** This augments {@link OnClickTest} with tests that exercise callbacks with multiple methods. */
public class OnItemSelectedTest {
  @Test public void defaultMethod() {
    JavaFileObject source = JavaFileObjects.forSourceString("test.Test", ""
        + "package test;\n"
        + "import butterknife.OnItemSelected;\n"
        + "public class Test {\n"
        + "  @OnItemSelected(1) void doStuff() {}\n"
        + "}"
    );

    JavaFileObject bindingSource = JavaFileObjects.forSourceString("test/Test_ViewBinding", ""
        + "package test;\n"
        + "import android.view.View;\n"
        + "import android.widget.AdapterView;\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"
        + "  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 'doStuff'\");\n"
        + "    view1 = view;\n"
        + "    ((AdapterView<?>) view).setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {\n"
        + "      @Override\n"
        + "      public void onItemSelected(AdapterView<?> p0, View p1, int p2, long p3) {\n"
        + "        target.doStuff();\n"
        + "      }\n"
        + "      @Override\n"
        + "      public void onNothingSelected(AdapterView<?> p0) {\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"
        + "    ((AdapterView<?>) view1).setOnItemSelectedListener(null);\n"
        + "    view1 = null;\n"
        + "  }\n"
        + "}"
    );

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

  @Test public void nonDefaultMethod() {
    JavaFileObject source = JavaFileObjects.forSourceString("test.Test", ""
        + "package test;"
        + "import butterknife.OnItemSelected;"
        + "import static butterknife.OnItemSelected.Callback.NOTHING_SELECTED;"
        + "public class Test {"
        + "  @OnItemSelected(value = 1, callback = NOTHING_SELECTED)"
        + "  void doStuff() {}"
        + "}"
    );

    JavaFileObject bindingSource = JavaFileObjects.forSourceString("test/Test_ViewBinding", ""
        + "package test;\n"
        + "import android.view.View;\n"
        + "import android.widget.AdapterView;\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"
        + "  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 'doStuff'\");\n"
        + "    view1 = view;\n"
        + "    ((AdapterView<?>) view).setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {\n"
        + "      @Override\n"
        + "      public void onItemSelected(AdapterView<?> p0, View p1, int p2, long p3) {\n"
        + "      }\n"
        + "      @Override\n"
        + "      public void onNothingSelected(AdapterView<?> p0) {\n"
        + "        target.doStuff();\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"
        + "    ((AdapterView<?>) view1).setOnItemSelectedListener(null);\n"
        + "    view1 = null;\n"
        + "  }\n"
        + "}"
    );

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

  @Test public void allMethods() {
    JavaFileObject source = JavaFileObjects.forSourceString("test.Test", ""
        + "package test;"
        + "import butterknife.OnItemSelected;"
        + "import static butterknife.OnItemSelected.Callback.NOTHING_SELECTED;"
        + "public class Test {"
        + "  @OnItemSelected(1)"
        + "  void onItemSelected() {}"
        + "  @OnItemSelected(value = 1, callback = NOTHING_SELECTED)"
        + "  void onNothingSelected() {}"
        + "}"
    );

    JavaFileObject bindingSource = JavaFileObjects.forSourceString("test/Test_ViewBinding", ""
        + "package test;\n"
        + "import android.view.View;\n"
        + "import android.widget.AdapterView;\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"
        + "  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 'onItemSelected' and method 'onNothingSelected'\");\n"
        + "    view1 = view;\n"
        + "    ((AdapterView<?>) view).setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {\n"
        + "      @Override\n"
        + "      public void onItemSelected(AdapterView<?> p0, View p1, int p2, long p3) {\n"
        + "        target.onItemSelected();\n"
        + "      }\n"
        + "      @Override\n"
        + "      public void onNothingSelected(AdapterView<?> p0) {\n"
        + "        target.onNothingSelected();\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"
        + "    ((AdapterView<?>) view1).setOnItemSelectedListener(null);\n"
        + "    view1 = null;\n"
        + "  }\n"
        + "}"
    );

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

  @Test public void multipleBindingPermutation() {
    JavaFileObject source = JavaFileObjects.forSourceString("test.Test", ""
        + "package test;"
        + "import butterknife.OnItemSelected;"
        + "import static butterknife.OnItemSelected.Callback.NOTHING_SELECTED;"
        + "public class Test {"
        + "  @OnItemSelected({ 1, 2 })"
        + "  void onItemSelected() {}"
        + "  @OnItemSelected(value = { 1, 3 }, callback = NOTHING_SELECTED)"
        + "  void onNothingSelected() {}"
        + "}"
    );

    JavaFileObject bindingSource = JavaFileObjects.forSourceString("test/Test_ViewBinding", ""
        + "package test;\n"
        + "import android.view.View;\n"
        + "import android.widget.AdapterView;\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"
        + "  private View view1;\n"
        + "  private View view2;\n"
        + "  private View view3;\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 'onItemSelected' and method 'onNothingSelected'\");\n"
        + "    view1 = view;\n"
        + "    ((AdapterView<?>) view).setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {\n"
        + "      @Override\n"
        + "      public void onItemSelected(AdapterView<?> p0, View p1, int p2, long p3) {\n"
        + "        target.onItemSelected();\n"
        + "      }\n"
        + "      @Override\n"
        + "      public void onNothingSelected(AdapterView<?> p0) {\n"
        + "        target.onNothingSelected();\n"
        + "      }\n"
        + "    });\n"
        + "    view = Utils.findRequiredView(source, 2, \"method 'onItemSelected'\");\n"
        + "    view2 = view;\n"
        + "    ((AdapterView<?>) view).setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {\n"
        + "      @Override\n"
        + "      public void onItemSelected(AdapterView<?> p0, View p1, int p2, long p3) {\n"
        + "        target.onItemSelected();\n"
        + "      }\n"
        + "      @Override\n"
        + "      public void onNothingSelected(AdapterView<?> p0) {\n"
        + "      }\n"
        + "    });\n"
        + "    view = Utils.findRequiredView(source, 3, \"method 'onNothingSelected'\");\n"
        + "    view3 = view;\n"
        + "    ((AdapterView<?>) view).setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {\n"
        + "      @Override\n"
        + "      public void onItemSelected(AdapterView<?> p0, View p1, int p2, long p3) {\n"
        + "      }\n"
        + "      @Override\n"
        + "      public void onNothingSelected(AdapterView<?> p0) {\n"
        + "        target.onNothingSelected();\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"
        + "    ((AdapterView<?>) view1).setOnItemSelectedListener(null);\n"
        + "    view1 = null;\n"
        + "    ((AdapterView<?>) view2).setOnItemSelectedListener(null);\n"
        + "    view2 = null;\n"
        + "    ((AdapterView<?>) view3).setOnItemSelectedListener(null);\n"
        + "    view3 = null;\n"
        + "  }\n"
        + "}"
    );

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