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Validating Array Binding Annotations in ButterKnife

This test suite validates the functionality of array binding in ButterKnife, focusing on the @BindArray annotation implementation. It ensures proper handling of TypedArray resources and validates type safety constraints for array bindings.

Test Coverage Overview

The test suite provides comprehensive coverage of the @BindArray annotation functionality.

Key areas tested include:

TypedArray resource binding validation
Type safety enforcement for array bindings
Generated binding code verification
Error handling for unsupported array types

Implementation Analysis

The testing approach utilizes JUnit framework with Google’s compile-testing library for annotation processing validation. The tests employ a combination of positive and negative test cases to verify both successful compilation scenarios and proper error handling.

Key patterns include:

Compile-time annotation processing verification
Generated code structure validation
Resource binding implementation checking

Technical Details

Testing tools and configuration:

JUnit test framework
ButterKnifeProcessor for annotation processing
JavaFileObjects for source code manipulation
Google Truth assertions for compile-time validation
Custom compiler options for processing verification

Best Practices Demonstrated

The test suite exemplifies high-quality testing practices through thorough validation of both positive and negative scenarios.

Notable practices include:

Explicit error message validation
Generated code structure verification
Comprehensive type safety checking
Clean test organization with clear separation of concerns

jakewharton/butterknife

butterknife-runtime/src/test/java/butterknife/BindArrayTest.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 BindArrayTest {
  @Test public void typedArray() throws Exception {
    JavaFileObject source = JavaFileObjects.forSourceString("test.Test", ""
        + "package test;\n"
        + "import butterknife.BindArray;\n"
        + "import android.content.res.TypedArray;\n"
        + "public class Test {\n"
        + "  @BindArray(1) TypedArray 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"
        + "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"
        + "    Resources res = context.getResources();\n"
        + "    target.one = res.obtainTypedArray(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 typeMustBeSupported() {
    JavaFileObject source = JavaFileObjects.forSourceString("test.Test", ""
        + "package test;\n"
        + "import butterknife.BindArray;\n"
        + "public class Test {\n"
        + "  @BindArray(1) String one;\n"
        + "}"
    );

    assertAbout(javaSource()).that(source)
        .processedWith(new ButterKnifeProcessor())
        .failsToCompile()
        .withErrorContaining(
            "@BindArray field type must be one of: String[], int[], CharSequence[], "
                + "android.content.res.TypedArray. (test.Test.one)")
        .in(source).onLine(4);
  }
}