Back to Repositories

Validating Dimension Binding Type Safety in ButterKnife

This test suite validates the dimension binding functionality in Butterknife, specifically focusing on type validation for the @BindDimen annotation. It ensures proper error handling when incorrect data types are used for dimension bindings.

Test Coverage Overview

The test coverage focuses on validation of the @BindDimen annotation’s type constraints in Butterknife. It verifies error handling when attempting to bind dimension resources to incompatible types.

Tests type validation for dimension bindings
Validates error messaging for incorrect type usage
Ensures proper exception handling

Implementation Analysis

The testing approach uses JUnit to verify type safety in Butterknife’s dimension binding mechanism. It employs a negative testing pattern to confirm proper failure handling when attempting to bind a dimension resource to a String field instead of the required int or float types.

Uses reflection-based testing
Implements failure scenario validation
Leverages Truth assertions for detailed error verification

Technical Details

JUnit test framework
Google Truth assertion library
Butterknife view binding library
Custom ViewTree test utility
Android dimension resource binding

Best Practices Demonstrated

The test demonstrates excellent practices in validation testing, including proper exception handling verification and detailed error message validation. It follows a clear structure for negative testing scenarios and uses appropriate assertion methods.

Clear test method naming
Proper exception handling verification
Specific error message validation
Isolated test scope

jakewharton/butterknife

butterknife-integration-test/src/androidTestReflect/java/com/example/butterknife/functional/BindDimenFailureTest.java

            
package com.example.butterknife.functional;

import android.view.View;
import butterknife.BindDimen;
import butterknife.ButterKnife;
import org.junit.Test;

import static com.google.common.truth.Truth.assertThat;
import static org.junit.Assert.fail;

public final class BindDimenFailureTest {
  private final View tree = ViewTree.create(1);

  static class Target {
    @BindDimen(1) String actual;
  }

  @Test public void typeMustBeIntOrFloat() {
    Target target = new Target();

    try {
      ButterKnife.bind(target, tree);
      fail();
    } catch (IllegalStateException e) {
      assertThat(e).hasMessageThat()
          .isEqualTo("@BindDimen field type must be 'int' or 'float'. "
              + "(com.example.butterknife.functional.BindDimenFailureTest$Target.actual)");
    }
  }
}