Back to Repositories

Validating String Resource Binding Types in Butterknife

This test suite validates the @BindString annotation functionality in the Butterknife library, focusing on type validation for string resource bindings. It ensures proper compile-time checks for field type requirements when using the annotation.

Test Coverage Overview

The test suite provides targeted coverage for the @BindString annotation’s type validation mechanism.

Key areas tested include:

Field type validation for String resources
Compile-time error handling for incorrect type usage
Annotation processing validation

Implementation Analysis

The testing approach uses compile-time verification through the ButterKnifeProcessor. It leverages JavaFileObjects for source code generation and validation, implementing a robust compile-time testing strategy that catches type mismatches early in the development cycle.

The test utilizes Truth assertions and JavaSourceSubjectFactory for precise error message validation.

Technical Details

Testing tools and configuration:

JUnit test framework
Google Truth assertion library
Compile-time testing utilities
ButterKnifeProcessor for annotation processing
JavaFileObjects for source code manipulation

Best Practices Demonstrated

The test exemplifies several testing best practices in annotation processing validation.

Notable practices include:

Precise error message verification
Isolated test cases
Clear test method naming
Comprehensive compile-time validation
Effective use of testing utilities

jakewharton/butterknife

butterknife-runtime/src/test/java/butterknife/BindStringTest.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 BindStringTest {
  @Test public void typeMustBeString() {
    JavaFileObject source = JavaFileObjects.forSourceString("test.Test", ""
        + "package test;\n"
        + "import butterknife.BindString;\n"
        + "public class Test {\n"
        + "  @BindString(1) boolean one;\n"
        + "}"
    );

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