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Validating Color Resource Binding Implementation in ButterKnife

This test suite validates the @BindColor annotation functionality in ButterKnife, focusing on color resource binding for Android applications. The tests verify both integer color values and ColorStateList handling, ensuring proper SDK version compatibility and type safety.

Test Coverage Overview

The test suite provides comprehensive coverage of @BindColor annotation functionality:

Simple integer color binding for SDK 23+
ColorStateList binding validation
Type validation and error handling
View binding and context handling

Key edge cases include type safety checks and SDK version compatibility verification.

Implementation Analysis

The testing approach utilizes JUnit framework with Google’s compile-testing library for annotation processing validation. Tests implement a combination of positive and negative scenarios, verifying both successful compilation cases and proper error handling. The implementation leverages JavaFileObjects for source code generation testing.

Technical Details

Testing tools and configuration:

ButterKnifeProcessor for annotation processing
JavaFileObjects for test source creation
Compiler options including -Xlint:-processing
SDK version specification via -Abutterknife.minSdk=23
Truth assertion library for compile-time validation

Best Practices Demonstrated

The test suite exemplifies several testing best practices:

Isolated test cases for distinct functionality
Comprehensive error message validation
Generated code verification
Clear test method naming conventions
Proper separation of concerns between different binding types

jakewharton/butterknife

butterknife-runtime/src/test/java/butterknife/BindColorTest.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 final class BindColorTest {
  @Test public void simpleIntSdk23() {
    JavaFileObject source = JavaFileObjects.forSourceString("test.Test", ""
        + "package test;\n"
        + "import butterknife.BindColor;\n"
        + "public class Test {\n"
        + "  @BindColor(1) 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.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"
        + "  /**\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"
        + "    target.one = context.getColor(1);\n"
        + "  }\n"
        + "  @Override\n"
        + "  @CallSuper\n"
        + "  public void unbind() {\n"
        + "  }\n"
        + "}"
    );

    assertAbout(javaSource()).that(source)
        .withCompilerOptions("-Xlint:-processing", "-Abutterknife.minSdk=23")
        .processedWith(new ButterKnifeProcessor())
        .compilesWithoutWarnings()
        .and()
        .generatesSources(bindingSource);
  }

  @Test public void simpleColorStateListSdk23() {
    JavaFileObject source = JavaFileObjects.forSourceString("test.Test", ""
        + "package test;\n"
        + "import android.content.res.ColorStateList;\n"
        + "import butterknife.BindColor;\n"
        + "public class Test {\n"
        + "  @BindColor(1) ColorStateList 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.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"
        + "  /**\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"
        + "    target.one = context.getColorStateList(1);\n"
        + "  }\n"
        + "  @Override\n"
        + "  @CallSuper\n"
        + "  public void unbind() {\n"
        + "  }\n"
        + "}"
    );

    assertAbout(javaSource()).that(source)
        .withCompilerOptions("-Xlint:-processing", "-Abutterknife.minSdk=23")
        .processedWith(new ButterKnifeProcessor())
        .compilesWithoutWarnings()
        .and()
        .generatesSources(bindingSource);
  }

  @Test public void typeMustBeIntOrColorStateList() {
    JavaFileObject source = JavaFileObjects.forSourceString("test.Test", ""
        + "package test;\n"
        + "import butterknife.BindColor;\n"
        + "public class Test {\n"
        + "  @BindColor(1) String one;\n"
        + "}"
    );

    assertAbout(javaSource()).that(source)
        .processedWith(new ButterKnifeProcessor())
        .failsToCompile()
        .withErrorContaining("@BindColor field type must be 'int' or 'ColorStateList'. (test.Test.one)")
        .in(source).onLine(4);
  }
}