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Validating Keyframe Animation Timing in Lottie Android

This test suite validates the Keyframe functionality in Lottie Android’s animation system. It focuses on verifying keyframe timing, progression, and interpolation mechanics that are crucial for smooth animations in the Lottie library.

Test Coverage Overview

The test suite covers essential keyframe animation functionality in Lottie Android.

Key areas tested include:

Keyframe start and end frame synchronization
Frame progression validation
Animation timing consistency
Composition initialization verification

Implementation Analysis

The testing approach employs JUnit to verify keyframe timing mechanics.

Technical implementation features:

Linear interpolation testing
Composition initialization with multiple parameters
Precise floating-point comparisons for frame timing
Direct keyframe object instantiation and validation

Technical Details

Testing infrastructure includes:

JUnit 4 testing framework
Android graphics and animation components
LottieComposition test initialization
Custom Keyframe class testing
LinearInterpolator for animation timing

Best Practices Demonstrated

The test implementation showcases robust testing practices for animation systems.

Notable practices include:

Precise floating-point equality assertions
Comprehensive composition setup
Clear test method naming
Isolated keyframe testing
Proper test initialization patterns

airbnb/lottie-android

lottie/src/test/java/com/airbnb/lottie/value/KeyframeTest.java

            
package com.airbnb.lottie.value;

import static org.junit.Assert.*;

import android.graphics.Rect;
import android.view.animation.LinearInterpolator;
import androidx.collection.LongSparseArray;
import androidx.collection.SparseArrayCompat;
import com.airbnb.lottie.LottieComposition;
import org.junit.Test;

import java.util.ArrayList;
import java.util.HashMap;

public class KeyframeTest {

  @Test
  public void testStartFrame() {
    LottieComposition composition = new LottieComposition();
    composition.init(
        new Rect(),
        0f,
        504.99f,
        60f,
        new ArrayList<>(),
        new LongSparseArray<>(),
        new HashMap<>(),
        new HashMap<>(),
        1f,
        new SparseArrayCompat<>(),
        new HashMap<>(),
        new ArrayList<>(),
        0,
        0
    );
    Keyframe<Float> keyframe1 = new Keyframe<>(composition, 200f, 321f, new LinearInterpolator(), 28f, 48f);
    Keyframe<Float> keyframe2 = new Keyframe<>(composition, 321f, 300f, new LinearInterpolator(), 48f, 56f);
    assertEquals(keyframe2.getStartProgress(), keyframe1.getEndProgress(), 0f);
  }
}