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Validating BindBitmap Type Validation in ButterKnife

This test suite validates the error handling of ButterKnife’s @BindBitmap annotation when used with incorrect field types. It specifically tests the failure scenario where a String field is annotated instead of the required Bitmap type.

Test Coverage Overview

The test coverage focuses on validating error handling for improper @BindBitmap usage in ButterKnife.

Tests field type validation for @BindBitmap annotation
Verifies appropriate exception throwing
Validates error message content

Implementation Analysis

The testing approach employs JUnit to verify ButterKnife’s binding failure behavior.

The test utilizes a mock view tree and attempts to bind an incorrectly typed field, expecting an IllegalStateException with a specific error message. The implementation leverages Truth assertions for precise error message validation.

Technical Details

JUnit test framework
Google Truth assertion library
ButterKnife view binding library
Mock view tree for testing
Custom Target class with @BindBitmap annotation

Best Practices Demonstrated

The test exhibits strong error handling validation practices by explicitly testing for incorrect usage scenarios.

Clear test method naming
Proper exception handling and verification
Specific error message validation
Isolated test case structure

jakewharton/butterknife

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

            
package com.example.butterknife.functional;

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

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

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

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

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

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