Back to Repositories

Validating BindViews Annotation Error Handling in Butterknife

This integration test suite validates error handling and failure scenarios for the BindViews annotation in Butterknife. It ensures proper validation of view bindings and enforces type safety requirements for collections and arrays.

Test Coverage Overview

The test suite comprehensively covers failure scenarios for the @BindViews annotation, including:

Empty ID array validation
Generic type requirements for collections
Supported collection type verification
View type validation for lists and arrays

Each test case verifies appropriate error messages and exception handling.

Implementation Analysis

The implementation uses JUnit’s testing framework with Truth assertions for precise error message validation. The tests follow a consistent pattern of attempting invalid bindings and verifying the resulting IllegalStateException messages. Each test case isolates a specific validation rule of the BindViews annotation.

Technical Details

Testing tools and configuration include:

JUnit test framework
Google Truth assertion library
Custom ViewTree test helper
ButterKnife view binding library
Android View system integration

Best Practices Demonstrated

The test suite exemplifies several testing best practices:

Isolated test cases for each failure scenario
Clear test method naming conventions
Precise error message validation
Proper exception handling verification
Clean test class organization with static inner classes for test cases

jakewharton/butterknife

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

            
package com.example.butterknife.functional;

import android.view.View;
import butterknife.BindViews;
import butterknife.ButterKnife;
import java.util.Deque;
import java.util.List;
import org.junit.Test;

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

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

  static class NoIds {
    @BindViews({}) View[] actual;
  }

  @Test public void failsIfNoIds() {
    NoIds target = new NoIds();

    try {
      ButterKnife.bind(target, tree);
      fail();
    } catch (IllegalStateException e) {
      assertThat(e).hasMessageThat()
          .isEqualTo("@BindViews must specify at least one ID. "
              + "(com.example.butterknife.functional.BindViewsFailureTest$NoIds.actual)");
    }
  }

  static class NoGenericType {
    @BindViews(1) List actual;
  }

  @Test public void failsIfNoGenericType() {
    NoGenericType target = new NoGenericType();

    try {
      ButterKnife.bind(target, tree);
      fail();
    } catch (IllegalStateException e) {
      assertThat(e).hasMessageThat()
          .isEqualTo("@BindViews List must have a generic component. "
              + "(com.example.butterknife.functional.BindViewsFailureTest$NoGenericType.actual)");
    }
  }

  static class BadCollection {
    @BindViews(1) Deque<View> actual;
  }

  @Test public void failsIfUnsupportedCollection() {
    BadCollection target = new BadCollection();

    try {
      ButterKnife.bind(target, tree);
      fail();
    } catch (IllegalStateException e) {
      assertThat(e).hasMessageThat()
          .isEqualTo("@BindViews must be a List or array. "
              + "(com.example.butterknife.functional.BindViewsFailureTest$BadCollection.actual)");
    }
  }

  static class ListNotView {
    @BindViews(1) List<String> actual;
  }

  @Test public void failsIfGenericNotView() {
    ListNotView target = new ListNotView();

    try {
      ButterKnife.bind(target, tree);
      fail();
    } catch (IllegalStateException e) {
      assertThat(e).hasMessageThat()
          .isEqualTo("@BindViews List or array type must extend from View or be an interface. "
              + "(com.example.butterknife.functional.BindViewsFailureTest$ListNotView.actual)");
    }
  }

  static class ArrayNotView {
    @BindViews(1) List<String> actual;
  }

  @Test public void failsIfArrayNotView() {
    ArrayNotView target = new ArrayNotView();

    try {
      ButterKnife.bind(target, tree);
      fail();
    } catch (IllegalStateException e) {
      assertThat(e).hasMessageThat()
          .isEqualTo("@BindViews List or array type must extend from View or be an interface. "
              + "(com.example.butterknife.functional.BindViewsFailureTest$ArrayNotView.actual)");
    }
  }
}