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Validating BindFont Annotation Error Handling in ButterKnife

This test suite validates error handling and failure cases for the BindFont annotation in ButterKnife, focusing on type validation and style constraints. It ensures proper exception handling when binding fonts with incorrect configurations.

Test Coverage Overview

The test suite covers critical validation scenarios for the BindFont annotation functionality.

Tests field type validation requiring Typeface objects
Verifies font style validation for SDK version 24 and above
Examines error message accuracy for invalid configurations
Tests boundary conditions for font binding failures

Implementation Analysis

The implementation uses JUnit 4 with AndroidX test filters for SDK-specific testing. It employs a systematic approach to validation testing through targeted test cases that verify exception handling.

The tests utilize mock views and custom target classes to simulate real-world usage scenarios, with explicit verification of error messages using Truth assertions.

Technical Details

JUnit 4 testing framework
AndroidX test filters for SDK version control
Google Truth assertion library
Custom ViewTree implementation for view hierarchy simulation
ButterKnife annotation processing

Best Practices Demonstrated

The test suite exemplifies robust error handling validation practices with clear test case isolation and specific assertion checks.

Proper test method naming conventions
Specific error message validation
SDK version-specific test annotations
Clean test class organization with static inner classes

jakewharton/butterknife

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

            
package com.example.butterknife.functional;

import android.graphics.Typeface;
import android.view.View;
import androidx.test.filters.SdkSuppress;
import butterknife.BindFont;
import butterknife.ButterKnife;
import com.example.butterknife.test.R;
import org.junit.Test;

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

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

  static class TargetType {
    @BindFont(1) String actual;
  }

  @Test public void typeMustBeTypeface() {
    TargetType target = new TargetType();

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

  static class TargetStyle {
    @BindFont(value = R.font.inconsolata_regular, style = 5) Typeface actual;
  }

  @SdkSuppress(minSdkVersion = 24) // AndroidX problems on earlier versions
  @Test public void styleMustBeValid() {
    TargetStyle target = new TargetStyle();

    try {
      ButterKnife.bind(target, tree);
      fail();
    } catch (IllegalStateException e) {
      assertThat(e).hasMessageThat()
          .isEqualTo("@BindFont style must be NORMAL, BOLD, ITALIC, or BOLD_ITALIC. "
              + "(com.example.butterknife.functional.BindFontFailureTest$TargetStyle.actual)");
    }
  }
}