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Testing Gamma Color Evaluation Mechanics in lottie-android

This test suite validates the GammaEvaluator utility class in the Lottie Android animation library, focusing on color interpolation functionality. The tests ensure accurate gamma correction calculations when evaluating color transitions, particularly for identical color values.

Test Coverage Overview

The test coverage focuses on the GammaEvaluator’s behavior when processing identical color values across the entire RGB spectrum. It systematically verifies:

Complete color range testing from 0x000000 to 0xffffff
Consistent color evaluation with fixed fraction value (0.3f)
Identity preservation when source and target colors match

Implementation Analysis

The testing approach employs JUnit framework with a comprehensive loop-based verification strategy. It utilizes a systematic iteration through all possible color values to ensure thorough coverage of the gamma evaluation logic.

The implementation leverages Hamcrest matchers for assertions, providing clear and expressive test validations for color equality checks.

Technical Details

Testing Infrastructure:

JUnit 4 testing framework
Hamcrest assertion library
Hexadecimal color value iteration
Static assertion methods
Single test method validation approach

Best Practices Demonstrated

The test exemplifies several testing best practices:

Exhaustive input space coverage
Clear test method naming convention
Focused test scope with single responsibility
Efficient loop-based verification
Use of descriptive assertion messages

airbnb/lottie-android

lottie/src/test/java/com/airbnb/lottie/utils/GammaEvaluatorTest.java

            
package com.airbnb.lottie.utils;

import org.junit.Test;

import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.core.Is.is;

public class GammaEvaluatorTest {
  @Test
  public void testEvaluateForSameColorValues() {
    for (int color = 0x000000; color <= 0xffffff; color++) {
      int actual = GammaEvaluator.evaluate(0.3f, color, color);
      assertThat(actual, is(color));
    }
  }
}