easings

FlexLove.lua

@@ -33,6 +33,8 @@ local Element = req("Element")
 local Animation = req("Animation")
 ---@type AnimationGroup
 local AnimationGroup = req("AnimationGroup")
+---@type Easing
+local Easing = req("Easing")
 ---@type Color
 local Color = req("Color")
 ---@type Theme
@@ -1120,6 +1122,7 @@ end
 
 flexlove.Animation = Animation
 flexlove.AnimationGroup = AnimationGroup
+flexlove.Easing = Easing
 flexlove.Color = Color
 flexlove.Theme = Theme
 flexlove.enums = enums

modules/Animation.lua

@@ -4,54 +4,19 @@
 -- ErrorHandler dependency (injected via initializeErrorHandler)
 local ErrorHandler = nil
 
---- Easing functions for animations
----@type table<string, EasingFunction>
-local Easing = {
-  linear = function(t)
-    return t
-  end,
+-- Easing module for easing functions
+local Easing = require("modules.Easing")
+---@class Keyframe
+---@field at number Normalized time position (0-1)
+---@field values table Property values at this keyframe
+---@field easing string|EasingFunction? Easing to use between this and next keyframe
 
-  easeInQuad = function(t)
-    return t * t
-  end,
-  easeOutQuad = function(t)
-    return t * (2 - t)
-  end,
-  easeInOutQuad = function(t)
-    return t < 0.5 and 2 * t * t or -1 + (4 - 2 * t) * t
-  end,
-
-  easeInCubic = function(t)
-    return t * t * t
-  end,
-  easeOutCubic = function(t)
-    local t1 = t - 1
-    return t1 * t1 * t1 + 1
-  end,
-  easeInOutCubic = function(t)
-    return t < 0.5 and 4 * t * t * t or (t - 1) * (2 * t - 2) * (2 * t - 2) + 1
-  end,
-
-  easeInQuart = function(t)
-    return t * t * t * t
-  end,
-  easeOutQuart = function(t)
-    local t1 = t - 1
-    return 1 - t1 * t1 * t1 * t1
-  end,
-
-  easeInExpo = function(t)
-    return t == 0 and 0 or math.pow(2, 10 * (t - 1))
-  end,
-  easeOutExpo = function(t)
-    return t == 1 and 1 or 1 - math.pow(2, -10 * t)
-  end,
-}
 ---@class AnimationProps
 ---@field duration number Duration in seconds
 ---@field start table Starting values (can contain: width, height, opacity, x, y, gap, imageOpacity, backgroundColor, borderColor, textColor, padding, margin, cornerRadius, etc.)
 ---@field final table Final values (same properties as start)
 ---@field easing string? Easing function name (default: "linear")
+---@field keyframes Keyframe[]? Array of keyframes for complex animations
 ---@field transform table? Additional transform properties
 ---@field transition table? Transition properties
 ---@field onStart function? Called when animation starts: (animation, element)
@@ -65,6 +30,7 @@ local Easing = {
 ---@field final table Final values
 ---@field elapsed number Elapsed time in seconds
 ---@field easing EasingFunction Easing function
+---@field keyframes Keyframe[]? Array of keyframes for complex animations
 ---@field transform table? Additional transform properties
 ---@field transition table? Transition properties
 ---@field _cachedResult table Cached interpolation result
@@ -103,6 +69,7 @@ function Animation.new(props)
   self.duration = props.duration
   self.start = props.start
   self.final = props.final
+  self.keyframes = props.keyframes
   self.transform = props.transform
   self.transition = props.transition
   self.elapsed = 0
@@ -304,6 +271,98 @@ local function lerpTable(startTable, finalTable, easedT)
   return result
 end
 
+--- Find the two keyframes surrounding the current progress
+---@param progress number Current animation progress (0-1)
+---@return Keyframe prevFrame The keyframe before current progress
+---@return Keyframe nextFrame The keyframe after current progress
+function Animation:findKeyframes(progress)
+  if not self.keyframes or #self.keyframes < 2 then
+    return nil, nil
+  end
+  
+  -- Find surrounding keyframes
+  local prevFrame = self.keyframes[1]
+  local nextFrame = self.keyframes[#self.keyframes]
+  
+  for i = 1, #self.keyframes - 1 do
+    if progress >= self.keyframes[i].at and progress <= self.keyframes[i + 1].at then
+      prevFrame = self.keyframes[i]
+      nextFrame = self.keyframes[i + 1]
+      break
+    end
+  end
+  
+  return prevFrame, nextFrame
+end
+
+--- Interpolate between two keyframes
+---@param prevFrame Keyframe Starting keyframe
+---@param nextFrame Keyframe Ending keyframe
+---@param easedT number Eased time (0-1) for interpolation
+---@return table result Interpolated values
+function Animation:lerpKeyframes(prevFrame, nextFrame, easedT)
+  local result = {}
+  
+  -- Get all unique property keys
+  local keys = {}
+  for k in pairs(prevFrame.values) do keys[k] = true end
+  for k in pairs(nextFrame.values) do keys[k] = true end
+  
+  -- Define properties that should be animated as numbers
+  local numericProperties = {
+    "width", "height", "opacity", "x", "y", 
+    "gap", "imageOpacity", "scrollbarWidth",
+    "borderWidth", "fontSize", "lineHeight"
+  }
+  
+  -- Define properties that should be animated as Colors
+  local colorProperties = {
+    "backgroundColor", "borderColor", "textColor",
+    "scrollbarColor", "scrollbarBackgroundColor", "imageTint"
+  }
+  
+  -- Define properties that should be animated as tables
+  local tableProperties = {
+    "padding", "margin", "cornerRadius"
+  }
+  
+  -- Create lookup sets for faster property type checking
+  local numericSet = {}
+  for _, prop in ipairs(numericProperties) do numericSet[prop] = true end
+  
+  local colorSet = {}
+  for _, prop in ipairs(colorProperties) do colorSet[prop] = true end
+  
+  local tableSet = {}
+  for _, prop in ipairs(tableProperties) do tableSet[prop] = true end
+  
+  -- Interpolate each property
+  for key in pairs(keys) do
+    local startVal = prevFrame.values[key]
+    local finalVal = nextFrame.values[key]
+    
+    if numericSet[key] and type(startVal) == "number" and type(finalVal) == "number" then
+      result[key] = lerpNumber(startVal, finalVal, easedT)
+    elseif colorSet[key] and self._Color then
+      if startVal ~= nil and finalVal ~= nil then
+        result[key] = lerpColor(startVal, finalVal, easedT, self._Color)
+      end
+    elseif tableSet[key] and type(startVal) == "table" and type(finalVal) == "table" then
+      result[key] = lerpTable(startVal, finalVal, easedT)
+    elseif type(startVal) == type(finalVal) then
+      -- For unknown types, try numeric interpolation if they're numbers
+      if type(startVal) == "number" then
+        result[key] = lerpNumber(startVal, finalVal, easedT)
+      else
+        -- Otherwise use the final value
+        result[key] = finalVal
+      end
+    end
+  end
+  
+  return result
+end
+
 --- Calculate the current animated values between start and end states based on elapsed time
 --- Use this to get the interpolated properties to apply to your element
 ---@return table result Interpolated values {width?, height?, opacity?, x?, y?, backgroundColor?, ...}
@@ -315,6 +374,50 @@ function Animation:interpolate()
 
   local t = math.min(self.elapsed / self.duration, 1)
   
+  -- Handle keyframe animations
+  if self.keyframes and #self.keyframes >= 2 then
+    local prevFrame, nextFrame = self:findKeyframes(t)
+    
+    if prevFrame and nextFrame then
+      -- Calculate local progress between keyframes
+      local localProgress = 0
+      if nextFrame.at > prevFrame.at then
+        localProgress = (t - prevFrame.at) / (nextFrame.at - prevFrame.at)
+      end
+      
+      -- Apply per-keyframe easing
+      local easingFn = Easing.linear
+      if prevFrame.easing then
+        if type(prevFrame.easing) == "string" then
+          easingFn = Easing[prevFrame.easing] or Easing.linear
+        elseif type(prevFrame.easing) == "function" then
+          easingFn = prevFrame.easing
+        end
+      end
+      
+      local success, easedT = pcall(easingFn, localProgress)
+      if not success or type(easedT) ~= "number" or easedT ~= easedT or easedT == math.huge or easedT == -math.huge then
+        easedT = localProgress
+      end
+      
+      -- Interpolate between keyframes
+      local keyframeResult = self:lerpKeyframes(prevFrame, nextFrame, easedT)
+      
+      -- Copy to cached result
+      local result = self._cachedResult
+      for k in pairs(result) do
+        result[k] = nil
+      end
+      for k, v in pairs(keyframeResult) do
+        result[k] = v
+      end
+      
+      self._resultDirty = false
+      return result
+    end
+  end
+  
+  -- Standard interpolation (non-keyframe)
   -- Apply easing function with protection
   local success, easedT = pcall(self.easing, t)
   if not success or type(easedT) ~= "number" or easedT ~= easedT or easedT == math.huge or easedT == -math.huge then
@@ -651,6 +754,67 @@ function Animation.scale(duration, fromScale, toScale, easing)
   })
 end
 
+--- Create a keyframe-based animation with multiple waypoints and per-keyframe easing
+--- Use this for complex multi-step animations like bounce-in effects or CSS-style @keyframes
+---@param props {duration:number, keyframes:Keyframe[], onStart:function?, onUpdate:function?, onComplete:function?, onCancel:function?} Animation properties
+---@return Animation animation The keyframe animation
+function Animation.keyframes(props)
+  if not ErrorHandler then
+    ErrorHandler = require("modules.ErrorHandler")
+  end
+  
+  -- Validate input
+  if type(props) ~= "table" then
+    ErrorHandler.warn("Animation", "Animation.keyframes() requires a table argument. Using default values.")
+    props = {duration = 1, keyframes = {}}
+  end
+  
+  if type(props.duration) ~= "number" or props.duration <= 0 then
+    ErrorHandler.warn("Animation", "Keyframe animation duration must be a positive number. Using 1 second.")
+    props.duration = 1
+  end
+  
+  if type(props.keyframes) ~= "table" or #props.keyframes < 2 then
+    ErrorHandler.warn("Animation", "Keyframe animation requires at least 2 keyframes. Using empty animation.")
+    props.keyframes = {
+      {at = 0, values = {}},
+      {at = 1, values = {}}
+    }
+  end
+  
+  -- Sort keyframes by 'at' position
+  local sortedKeyframes = {}
+  for i, kf in ipairs(props.keyframes) do
+    if type(kf) == "table" and type(kf.at) == "number" and type(kf.values) == "table" then
+      table.insert(sortedKeyframes, kf)
+    end
+  end
+  
+  table.sort(sortedKeyframes, function(a, b) return a.at < b.at end)
+  
+  -- Ensure keyframes start at 0 and end at 1
+  if #sortedKeyframes > 0 then
+    if sortedKeyframes[1].at > 0 then
+      table.insert(sortedKeyframes, 1, {at = 0, values = sortedKeyframes[1].values})
+    end
+    if sortedKeyframes[#sortedKeyframes].at < 1 then
+      table.insert(sortedKeyframes, {at = 1, values = sortedKeyframes[#sortedKeyframes].values})
+    end
+  end
+  
+  -- Create animation with keyframes
+  return Animation.new({
+    duration = props.duration,
+    start = {},
+    final = {},
+    keyframes = sortedKeyframes,
+    onStart = props.onStart,
+    onUpdate = props.onUpdate,
+    onComplete = props.onComplete,
+    onCancel = props.onCancel,
+  })
+end
+
 --- Initialize ErrorHandler dependency
 ---@param errorHandler table The ErrorHandler module
 local function initializeErrorHandler(errorHandler)

modules/Easing.lua

@@ -0,0 +1,361 @@
+--- Easing functions for animations
+--- Provides 30+ easing functions for smooth animation transitions
+---
+--- Easing function type
+---@alias EasingFunction fun(t: number): number
+---
+---@class Easing
+local Easing = {}
+
+-- ============================================================================
+-- Linear
+-- ============================================================================
+
+---@type EasingFunction
+function Easing.linear(t)
+  return t
+end
+
+-- ============================================================================
+-- Quadratic (Quad)
+-- ============================================================================
+
+---@type EasingFunction
+function Easing.easeInQuad(t)
+  return t * t
+end
+
+---@type EasingFunction
+function Easing.easeOutQuad(t)
+  return t * (2 - t)
+end
+
+---@type EasingFunction
+function Easing.easeInOutQuad(t)
+  return t < 0.5 and 2 * t * t or -1 + (4 - 2 * t) * t
+end
+
+-- ============================================================================
+-- Cubic
+-- ============================================================================
+
+---@type EasingFunction
+function Easing.easeInCubic(t)
+  return t * t * t
+end
+
+---@type EasingFunction
+function Easing.easeOutCubic(t)
+  local t1 = t - 1
+  return t1 * t1 * t1 + 1
+end
+
+---@type EasingFunction
+function Easing.easeInOutCubic(t)
+  return t < 0.5 and 4 * t * t * t or (t - 1) * (2 * t - 2) * (2 * t - 2) + 1
+end
+
+-- ============================================================================
+-- Quartic (Quart)
+-- ============================================================================
+
+---@type EasingFunction
+function Easing.easeInQuart(t)
+  return t * t * t * t
+end
+
+---@type EasingFunction
+function Easing.easeOutQuart(t)
+  local t1 = t - 1
+  return 1 - t1 * t1 * t1 * t1
+end
+
+---@type EasingFunction
+function Easing.easeInOutQuart(t)
+  if t < 0.5 then
+    return 8 * t * t * t * t
+  else
+    local t1 = t - 1
+    return 1 - 8 * t1 * t1 * t1 * t1
+  end
+end
+
+-- ============================================================================
+-- Quintic (Quint)
+-- ============================================================================
+
+---@type EasingFunction
+function Easing.easeInQuint(t)
+  return t * t * t * t * t
+end
+
+---@type EasingFunction
+function Easing.easeOutQuint(t)
+  local t1 = t - 1
+  return 1 + t1 * t1 * t1 * t1 * t1
+end
+
+---@type EasingFunction
+function Easing.easeInOutQuint(t)
+  if t < 0.5 then
+    return 16 * t * t * t * t * t
+  else
+    local t1 = t - 1
+    return 1 + 16 * t1 * t1 * t1 * t1 * t1
+  end
+end
+
+-- ============================================================================
+-- Exponential (Expo)
+-- ============================================================================
+
+---@type EasingFunction
+function Easing.easeInExpo(t)
+  return t == 0 and 0 or math.pow(2, 10 * (t - 1))
+end
+
+---@type EasingFunction
+function Easing.easeOutExpo(t)
+  return t == 1 and 1 or 1 - math.pow(2, -10 * t)
+end
+
+---@type EasingFunction
+function Easing.easeInOutExpo(t)
+  if t == 0 then return 0 end
+  if t == 1 then return 1 end
+  
+  if t < 0.5 then
+    return 0.5 * math.pow(2, 20 * t - 10)
+  else
+    return 1 - 0.5 * math.pow(2, -20 * t + 10)
+  end
+end
+
+-- ============================================================================
+-- Sine
+-- ============================================================================
+
+---@type EasingFunction
+function Easing.easeInSine(t)
+  return 1 - math.cos(t * math.pi / 2)
+end
+
+---@type EasingFunction
+function Easing.easeOutSine(t)
+  return math.sin(t * math.pi / 2)
+end
+
+---@type EasingFunction
+function Easing.easeInOutSine(t)
+  return -(math.cos(math.pi * t) - 1) / 2
+end
+
+-- ============================================================================
+-- Circular (Circ)
+-- ============================================================================
+
+---@type EasingFunction
+function Easing.easeInCirc(t)
+  return 1 - math.sqrt(1 - t * t)
+end
+
+---@type EasingFunction
+function Easing.easeOutCirc(t)
+  local t1 = t - 1
+  return math.sqrt(1 - t1 * t1)
+end
+
+---@type EasingFunction
+function Easing.easeInOutCirc(t)
+  if t < 0.5 then
+    return (1 - math.sqrt(1 - 4 * t * t)) / 2
+  else
+    local t1 = -2 * t + 2
+    return (math.sqrt(1 - t1 * t1) + 1) / 2
+  end
+end
+
+-- ============================================================================
+-- Back (Overshoot)
+-- ============================================================================
+
+---@type EasingFunction
+function Easing.easeInBack(t)
+  local c1 = 1.70158
+  local c3 = c1 + 1
+  return c3 * t * t * t - c1 * t * t
+end
+
+---@type EasingFunction
+function Easing.easeOutBack(t)
+  local c1 = 1.70158
+  local c3 = c1 + 1
+  local t1 = t - 1
+  return 1 + c3 * t1 * t1 * t1 + c1 * t1 * t1
+end
+
+---@type EasingFunction
+function Easing.easeInOutBack(t)
+  local c1 = 1.70158
+  local c2 = c1 * 1.525
+  
+  if t < 0.5 then
+    return (2 * t * 2 * t * ((c2 + 1) * 2 * t - c2)) / 2
+  else
+    local t1 = 2 * t - 2
+    return (t1 * t1 * ((c2 + 1) * t1 + c2) + 2) / 2
+  end
+end
+
+-- ============================================================================
+-- Elastic (Spring)
+-- ============================================================================
+
+---@type EasingFunction
+function Easing.easeInElastic(t)
+  if t == 0 then return 0 end
+  if t == 1 then return 1 end
+  
+  local c4 = (2 * math.pi) / 3
+  return -math.pow(2, 10 * t - 10) * math.sin((t * 10 - 10.75) * c4)
+end
+
+---@type EasingFunction
+function Easing.easeOutElastic(t)
+  if t == 0 then return 0 end
+  if t == 1 then return 1 end
+  
+  local c4 = (2 * math.pi) / 3
+  return math.pow(2, -10 * t) * math.sin((t * 10 - 0.75) * c4) + 1
+end
+
+---@type EasingFunction
+function Easing.easeInOutElastic(t)
+  if t == 0 then return 0 end
+  if t == 1 then return 1 end
+  
+  local c5 = (2 * math.pi) / 4.5
+  
+  if t < 0.5 then
+    return -(math.pow(2, 20 * t - 10) * math.sin((20 * t - 11.125) * c5)) / 2
+  else
+    return (math.pow(2, -20 * t + 10) * math.sin((20 * t - 11.125) * c5)) / 2 + 1
+  end
+end
+
+-- ============================================================================
+-- Bounce
+-- ============================================================================
+
+---@type EasingFunction
+function Easing.easeOutBounce(t)
+  local n1 = 7.5625
+  local d1 = 2.75
+  
+  if t < 1 / d1 then
+    return n1 * t * t
+  elseif t < 2 / d1 then
+    local t1 = t - 1.5 / d1
+    return n1 * t1 * t1 + 0.75
+  elseif t < 2.5 / d1 then
+    local t1 = t - 2.25 / d1
+    return n1 * t1 * t1 + 0.9375
+  else
+    local t1 = t - 2.625 / d1
+    return n1 * t1 * t1 + 0.984375
+  end
+end
+
+---@type EasingFunction
+function Easing.easeInBounce(t)
+  return 1 - Easing.easeOutBounce(1 - t)
+end
+
+---@type EasingFunction
+function Easing.easeInOutBounce(t)
+  if t < 0.5 then
+    return (1 - Easing.easeOutBounce(1 - 2 * t)) / 2
+  else
+    return (1 + Easing.easeOutBounce(2 * t - 1)) / 2
+  end
+end
+
+-- ============================================================================
+-- Configurable Easing Factories
+-- ============================================================================
+
+--- Create a custom back easing function with configurable overshoot
+---@param overshoot number? Overshoot amount (default: 1.70158)
+---@return EasingFunction
+function Easing.back(overshoot)
+  overshoot = overshoot or 1.70158
+  local c3 = overshoot + 1
+  
+  return function(t)
+    return c3 * t * t * t - overshoot * t * t
+  end
+end
+
+--- Create a custom elastic easing function
+---@param amplitude number? Amplitude (default: 1)
+---@param period number? Period (default: 0.3)
+---@return EasingFunction
+function Easing.elastic(amplitude, period)
+  amplitude = amplitude or 1
+  period = period or 0.3
+  
+  return function(t)
+    if t == 0 then return 0 end
+    if t == 1 then return 1 end
+    
+    local s = period / 4
+    local a = amplitude
+    
+    if a < 1 then
+      a = 1
+      s = period / 4
+    else
+      s = period / (2 * math.pi) * math.asin(1 / a)
+    end
+    
+    return a * math.pow(2, -10 * t) * math.sin((t - s) * (2 * math.pi) / period) + 1
+  end
+end
+
+--- Get list of all available easing function names
+---@return string[] names Array of easing function names
+function Easing.list()
+  return {
+    -- Linear
+    "linear",
+    -- Quad
+    "easeInQuad", "easeOutQuad", "easeInOutQuad",
+    -- Cubic
+    "easeInCubic", "easeOutCubic", "easeInOutCubic",
+    -- Quart
+    "easeInQuart", "easeOutQuart", "easeInOutQuart",
+    -- Quint
+    "easeInQuint", "easeOutQuint", "easeInOutQuint",
+    -- Expo
+    "easeInExpo", "easeOutExpo", "easeInOutExpo",
+    -- Sine
+    "easeInSine", "easeOutSine", "easeInOutSine",
+    -- Circ
+    "easeInCirc", "easeOutCirc", "easeInOutCirc",
+    -- Back
+    "easeInBack", "easeOutBack", "easeInOutBack",
+    -- Elastic
+    "easeInElastic", "easeOutElastic", "easeInOutElastic",
+    -- Bounce
+    "easeInBounce", "easeOutBounce", "easeInOutBounce",
+  }
+end
+
+--- Get an easing function by name
+---@param name string Easing function name
+---@return EasingFunction? easing The easing function, or nil if not found
+function Easing.get(name)
+  return Easing[name]
+end
+
+return Easing

testing/__tests__/easing_test.lua

@@ -0,0 +1,310 @@
+local luaunit = require("testing.luaunit")
+require("testing.loveStub")
+
+local Easing = require("modules.Easing")
+local ErrorHandler = require("modules.ErrorHandler")
+local ErrorCodes = require("modules.ErrorCodes")
+
+-- Initialize ErrorHandler
+ErrorHandler.init({ ErrorCodes = ErrorCodes })
+
+TestEasing = {}
+
+function TestEasing:setUp()
+  -- Reset state before each test
+end
+
+-- Test that all easing functions exist
+function TestEasing:testAllEasingFunctionsExist()
+  local easings = {
+    -- Linear
+    "linear",
+    -- Quad
+    "easeInQuad", "easeOutQuad", "easeInOutQuad",
+    -- Cubic
+    "easeInCubic", "easeOutCubic", "easeInOutCubic",
+    -- Quart
+    "easeInQuart", "easeOutQuart", "easeInOutQuart",
+    -- Quint
+    "easeInQuint", "easeOutQuint", "easeInOutQuint",
+    -- Expo
+    "easeInExpo", "easeOutExpo", "easeInOutExpo",
+    -- Sine
+    "easeInSine", "easeOutSine", "easeInOutSine",
+    -- Circ
+    "easeInCirc", "easeOutCirc", "easeInOutCirc",
+    -- Back
+    "easeInBack", "easeOutBack", "easeInOutBack",
+    -- Elastic
+    "easeInElastic", "easeOutElastic", "easeInOutElastic",
+    -- Bounce
+    "easeInBounce", "easeOutBounce", "easeInOutBounce",
+  }
+  
+  for _, name in ipairs(easings) do
+    luaunit.assertNotNil(Easing[name], "Easing function " .. name .. " should exist")
+    luaunit.assertEquals(type(Easing[name]), "function", name .. " should be a function")
+  end
+end
+
+-- Test that all easing functions accept t parameter (0-1)
+function TestEasing:testEasingFunctionsAcceptParameter()
+  local result = Easing.linear(0.5)
+  luaunit.assertNotNil(result)
+  luaunit.assertEquals(type(result), "number")
+end
+
+-- Test linear easing
+function TestEasing:testLinear()
+  luaunit.assertEquals(Easing.linear(0), 0)
+  luaunit.assertEquals(Easing.linear(0.5), 0.5)
+  luaunit.assertEquals(Easing.linear(1), 1)
+end
+
+-- Test easeInQuad
+function TestEasing:testEaseInQuad()
+  luaunit.assertEquals(Easing.easeInQuad(0), 0)
+  luaunit.assertAlmostEquals(Easing.easeInQuad(0.5), 0.25, 0.01)
+  luaunit.assertEquals(Easing.easeInQuad(1), 1)
+end
+
+-- Test easeOutQuad
+function TestEasing:testEaseOutQuad()
+  luaunit.assertEquals(Easing.easeOutQuad(0), 0)
+  luaunit.assertAlmostEquals(Easing.easeOutQuad(0.5), 0.75, 0.01)
+  luaunit.assertEquals(Easing.easeOutQuad(1), 1)
+end
+
+-- Test easeInOutQuad
+function TestEasing:testEaseInOutQuad()
+  luaunit.assertEquals(Easing.easeInOutQuad(0), 0)
+  luaunit.assertAlmostEquals(Easing.easeInOutQuad(0.5), 0.5, 0.01)
+  luaunit.assertEquals(Easing.easeInOutQuad(1), 1)
+end
+
+-- Test easeInSine
+function TestEasing:testEaseInSine()
+  luaunit.assertEquals(Easing.easeInSine(0), 0)
+  local mid = Easing.easeInSine(0.5)
+  luaunit.assertTrue(mid > 0 and mid < 1, "easeInSine(0.5) should be between 0 and 1")
+  luaunit.assertAlmostEquals(Easing.easeInSine(1), 1, 0.01)
+end
+
+-- Test easeOutSine
+function TestEasing:testEaseOutSine()
+  luaunit.assertEquals(Easing.easeOutSine(0), 0)
+  local mid = Easing.easeOutSine(0.5)
+  luaunit.assertTrue(mid > 0 and mid < 1, "easeOutSine(0.5) should be between 0 and 1")
+  luaunit.assertAlmostEquals(Easing.easeOutSine(1), 1, 0.01)
+end
+
+-- Test easeInOutSine
+function TestEasing:testEaseInOutSine()
+  luaunit.assertEquals(Easing.easeInOutSine(0), 0)
+  luaunit.assertAlmostEquals(Easing.easeInOutSine(0.5), 0.5, 0.01)
+  luaunit.assertAlmostEquals(Easing.easeInOutSine(1), 1, 0.01)
+end
+
+-- Test easeInQuint
+function TestEasing:testEaseInQuint()
+  luaunit.assertEquals(Easing.easeInQuint(0), 0)
+  luaunit.assertAlmostEquals(Easing.easeInQuint(0.5), 0.03125, 0.01)
+  luaunit.assertEquals(Easing.easeInQuint(1), 1)
+end
+
+-- Test easeOutQuint
+function TestEasing:testEaseOutQuint()
+  luaunit.assertEquals(Easing.easeOutQuint(0), 0)
+  luaunit.assertAlmostEquals(Easing.easeOutQuint(0.5), 0.96875, 0.01)
+  luaunit.assertEquals(Easing.easeOutQuint(1), 1)
+end
+
+-- Test easeInCirc
+function TestEasing:testEaseInCirc()
+  luaunit.assertEquals(Easing.easeInCirc(0), 0)
+  local mid = Easing.easeInCirc(0.5)
+  luaunit.assertTrue(mid > 0 and mid < 1, "easeInCirc(0.5) should be between 0 and 1")
+  luaunit.assertAlmostEquals(Easing.easeInCirc(1), 1, 0.01)
+end
+
+-- Test easeOutCirc
+function TestEasing:testEaseOutCirc()
+  luaunit.assertEquals(Easing.easeOutCirc(0), 0)
+  local mid = Easing.easeOutCirc(0.5)
+  luaunit.assertTrue(mid > 0 and mid < 1, "easeOutCirc(0.5) should be between 0 and 1")
+  luaunit.assertAlmostEquals(Easing.easeOutCirc(1), 1, 0.01)
+end
+
+-- Test easeInOutCirc
+function TestEasing:testEaseInOutCirc()
+  luaunit.assertEquals(Easing.easeInOutCirc(0), 0)
+  luaunit.assertAlmostEquals(Easing.easeInOutCirc(0.5), 0.5, 0.01)
+  luaunit.assertAlmostEquals(Easing.easeInOutCirc(1), 1, 0.01)
+end
+
+-- Test easeInBack (should overshoot at start)
+function TestEasing:testEaseInBack()
+  luaunit.assertEquals(Easing.easeInBack(0), 0)
+  local early = Easing.easeInBack(0.3)
+  luaunit.assertTrue(early < 0, "easeInBack should go negative (overshoot) early on")
+  luaunit.assertAlmostEquals(Easing.easeInBack(1), 1, 0.001)
+end
+
+-- Test easeOutBack (should overshoot at end)
+function TestEasing:testEaseOutBack()
+  luaunit.assertAlmostEquals(Easing.easeOutBack(0), 0, 0.001)
+  local late = Easing.easeOutBack(0.7)
+  luaunit.assertTrue(late > 0.7, "easeOutBack should overshoot at the end")
+  luaunit.assertAlmostEquals(Easing.easeOutBack(1), 1, 0.01)
+end
+
+-- Test easeInElastic (should oscillate)
+function TestEasing:testEaseInElastic()
+  luaunit.assertEquals(Easing.easeInElastic(0), 0)
+  luaunit.assertAlmostEquals(Easing.easeInElastic(1), 1, 0.01)
+  -- Elastic should go negative at some point
+  local hasNegative = false
+  for i = 1, 9 do
+    local t = i / 10
+    if Easing.easeInElastic(t) < 0 then
+      hasNegative = true
+      break
+    end
+  end
+  luaunit.assertTrue(hasNegative, "easeInElastic should have negative values (oscillation)")
+end
+
+-- Test easeOutElastic (should oscillate)
+function TestEasing:testEaseOutElastic()
+  luaunit.assertEquals(Easing.easeOutElastic(0), 0)
+  luaunit.assertAlmostEquals(Easing.easeOutElastic(1), 1, 0.01)
+  -- Elastic should go above 1 at some point
+  local hasOvershoot = false
+  for i = 1, 9 do
+    local t = i / 10
+    if Easing.easeOutElastic(t) > 1 then
+      hasOvershoot = true
+      break
+    end
+  end
+  luaunit.assertTrue(hasOvershoot, "easeOutElastic should overshoot 1 (oscillation)")
+end
+
+-- Test easeInBounce
+function TestEasing:testEaseInBounce()
+  luaunit.assertEquals(Easing.easeInBounce(0), 0)
+  luaunit.assertAlmostEquals(Easing.easeInBounce(1), 1, 0.01)
+  -- Bounce should have multiple "bounces" (local minima)
+  local result = Easing.easeInBounce(0.5)
+  luaunit.assertTrue(result >= 0 and result <= 1, "easeInBounce should stay within 0-1 range")
+end
+
+-- Test easeOutBounce
+function TestEasing:testEaseOutBounce()
+  luaunit.assertEquals(Easing.easeOutBounce(0), 0)
+  luaunit.assertAlmostEquals(Easing.easeOutBounce(1), 1, 0.01)
+  -- Bounce should have bounces
+  local result = Easing.easeOutBounce(0.8)
+  luaunit.assertTrue(result >= 0 and result <= 1, "easeOutBounce should stay within 0-1 range")
+end
+
+-- Test easeInOutBounce
+function TestEasing:testEaseInOutBounce()
+  luaunit.assertEquals(Easing.easeInOutBounce(0), 0)
+  luaunit.assertAlmostEquals(Easing.easeInOutBounce(0.5), 0.5, 0.01)
+  luaunit.assertAlmostEquals(Easing.easeInOutBounce(1), 1, 0.01)
+end
+
+-- Test configurable back() factory
+function TestEasing:testBackFactory()
+  local customBack = Easing.back(2.5)
+  luaunit.assertEquals(type(customBack), "function")
+  luaunit.assertEquals(customBack(0), 0)
+  luaunit.assertEquals(customBack(1), 1)
+  -- Should overshoot with custom amount
+  local mid = customBack(0.3)
+  luaunit.assertTrue(mid < 0, "Custom back easing should overshoot")
+end
+
+-- Test configurable elastic() factory
+function TestEasing:testElasticFactory()
+  local customElastic = Easing.elastic(1.5, 0.4)
+  luaunit.assertEquals(type(customElastic), "function")
+  luaunit.assertEquals(customElastic(0), 0)
+  luaunit.assertAlmostEquals(customElastic(1), 1, 0.01)
+end
+
+-- Test Easing.list() method
+function TestEasing:testList()
+  local list = Easing.list()
+  luaunit.assertEquals(type(list), "table")
+  luaunit.assertEquals(#list, 31, "Should have exactly 31 easing functions")
+  
+  -- Check that linear is in the list
+  local hasLinear = false
+  for _, name in ipairs(list) do
+    if name == "linear" then
+      hasLinear = true
+      break
+    end
+  end
+  luaunit.assertTrue(hasLinear, "List should contain 'linear'")
+end
+
+-- Test Easing.get() method
+function TestEasing:testGet()
+  local linear = Easing.get("linear")
+  luaunit.assertNotNil(linear)
+  luaunit.assertEquals(type(linear), "function")
+  luaunit.assertEquals(linear(0.5), 0.5)
+  
+  -- Test non-existent easing
+  local nonExistent = Easing.get("nonExistentEasing")
+  luaunit.assertNil(nonExistent)
+end
+
+-- Test that all InOut easings are symmetric around 0.5
+function TestEasing:testInOutSymmetry()
+  local inOutEasings = {
+    "easeInOutQuad", "easeInOutCubic", "easeInOutQuart", "easeInOutQuint",
+    "easeInOutExpo", "easeInOutSine", "easeInOutCirc", "easeInOutBack",
+    "easeInOutElastic", "easeInOutBounce"
+  }
+  
+  for _, name in ipairs(inOutEasings) do
+    local easing = Easing[name]
+    -- At t=0.5, all InOut easings should be close to 0.5
+    local mid = easing(0.5)
+    luaunit.assertAlmostEquals(mid, 0.5, 0.1, name .. " should be close to 0.5 at t=0.5")
+  end
+end
+
+-- Test boundary conditions for all easings
+function TestEasing:testBoundaryConditions()
+  local easings = {
+    "linear",
+    "easeInQuad", "easeOutQuad", "easeInOutQuad",
+    "easeInCubic", "easeOutCubic", "easeInOutCubic",
+    "easeInQuart", "easeOutQuart", "easeInOutQuart",
+    "easeInQuint", "easeOutQuint", "easeInOutQuint",
+    "easeInExpo", "easeOutExpo", "easeInOutExpo",
+    "easeInSine", "easeOutSine", "easeInOutSine",
+    "easeInCirc", "easeOutCirc", "easeInOutCirc",
+    "easeInBack", "easeOutBack", "easeInOutBack",
+    "easeInElastic", "easeOutElastic", "easeInOutElastic",
+    "easeInBounce", "easeOutBounce", "easeInOutBounce",
+  }
+  
+  for _, name in ipairs(easings) do
+    local easing = Easing[name]
+    -- All easings should start at 0
+    local start = easing(0)
+    luaunit.assertAlmostEquals(start, 0, 0.01, name .. " should start at 0")
+    
+    -- All easings should end at 1
+    local finish = easing(1)
+    luaunit.assertAlmostEquals(finish, 1, 0.01, name .. " should end at 1")
+  end
+end
+
+os.exit(luaunit.LuaUnit.run())

testing/__tests__/keyframe_animation_test.lua

@@ -0,0 +1,353 @@
+local luaunit = require("testing.luaunit")
+require("testing.loveStub")
+
+local Animation = require("modules.Animation")
+local ErrorHandler = require("modules.ErrorHandler")
+local ErrorCodes = require("modules.ErrorCodes")
+
+-- Initialize ErrorHandler for Animation module
+ErrorHandler.init({ ErrorCodes = ErrorCodes })
+Animation.initializeErrorHandler(ErrorHandler)
+
+TestKeyframeAnimation = {}
+
+function TestKeyframeAnimation:setUp()
+  -- Reset state before each test
+end
+
+-- Test basic keyframe animation creation
+function TestKeyframeAnimation:testCreateKeyframeAnimation()
+  local anim = Animation.keyframes({
+    duration = 2,
+    keyframes = {
+      {at = 0, values = {x = 0, opacity = 0}},
+      {at = 1, values = {x = 100, opacity = 1}},
+    }
+  })
+  
+  luaunit.assertNotNil(anim)
+  luaunit.assertEquals(type(anim), "table")
+  luaunit.assertEquals(anim.duration, 2)
+  luaunit.assertNotNil(anim.keyframes)
+  luaunit.assertEquals(#anim.keyframes, 2)
+end
+
+-- Test keyframe animation with multiple waypoints
+function TestKeyframeAnimation:testMultipleWaypoints()
+  local anim = Animation.keyframes({
+    duration = 3,
+    keyframes = {
+      {at = 0,    values = {x = 0,   opacity = 0}},
+      {at = 0.25, values = {x = 50,  opacity = 1}},
+      {at = 0.75, values = {x = 150, opacity = 1}},
+      {at = 1,    values = {x = 200, opacity = 0}},
+    }
+  })
+  
+  luaunit.assertEquals(#anim.keyframes, 4)
+  luaunit.assertEquals(anim.keyframes[1].at, 0)
+  luaunit.assertEquals(anim.keyframes[2].at, 0.25)
+  luaunit.assertEquals(anim.keyframes[3].at, 0.75)
+  luaunit.assertEquals(anim.keyframes[4].at, 1)
+end
+
+-- Test keyframe sorting
+function TestKeyframeAnimation:testKeyframeSorting()
+  local anim = Animation.keyframes({
+    duration = 1,
+    keyframes = {
+      {at = 1,    values = {x = 100}},
+      {at = 0,    values = {x = 0}},
+      {at = 0.5,  values = {x = 50}},
+    }
+  })
+  
+  -- Should be sorted by 'at' position
+  luaunit.assertEquals(anim.keyframes[1].at, 0)
+  luaunit.assertEquals(anim.keyframes[2].at, 0.5)
+  luaunit.assertEquals(anim.keyframes[3].at, 1)
+end
+
+-- Test keyframe interpolation at start
+function TestKeyframeAnimation:testInterpolationAtStart()
+  local anim = Animation.keyframes({
+    duration = 1,
+    keyframes = {
+      {at = 0, values = {x = 0, opacity = 0}},
+      {at = 1, values = {x = 100, opacity = 1}},
+    }
+  })
+  
+  anim.elapsed = 0
+  local result = anim:interpolate()
+  
+  luaunit.assertNotNil(result.x)
+  luaunit.assertNotNil(result.opacity)
+  luaunit.assertAlmostEquals(result.x, 0, 0.01)
+  luaunit.assertAlmostEquals(result.opacity, 0, 0.01)
+end
+
+-- Test keyframe interpolation at end
+function TestKeyframeAnimation:testInterpolationAtEnd()
+  local anim = Animation.keyframes({
+    duration = 1,
+    keyframes = {
+      {at = 0, values = {x = 0, opacity = 0}},
+      {at = 1, values = {x = 100, opacity = 1}},
+    }
+  })
+  
+  anim.elapsed = 1
+  local result = anim:interpolate()
+  
+  luaunit.assertAlmostEquals(result.x, 100, 0.01)
+  luaunit.assertAlmostEquals(result.opacity, 1, 0.01)
+end
+
+-- Test keyframe interpolation at midpoint
+function TestKeyframeAnimation:testInterpolationAtMidpoint()
+  local anim = Animation.keyframes({
+    duration = 1,
+    keyframes = {
+      {at = 0, values = {x = 0}},
+      {at = 1, values = {x = 100}},
+    }
+  })
+  
+  anim.elapsed = 0.5
+  local result = anim:interpolate()
+  
+  luaunit.assertAlmostEquals(result.x, 50, 0.01)
+end
+
+-- Test per-keyframe easing
+function TestKeyframeAnimation:testPerKeyframeEasing()
+  local anim = Animation.keyframes({
+    duration = 1,
+    keyframes = {
+      {at = 0,   values = {x = 0},   easing = "easeInQuad"},
+      {at = 0.5, values = {x = 50},  easing = "linear"},
+      {at = 1,   values = {x = 100}},
+    }
+  })
+  
+  -- At t=0.25 (middle of first segment with easeInQuad)
+  anim.elapsed = 0.25
+  anim._resultDirty = true  -- Mark dirty to force recalculation
+  local result1 = anim:interpolate()
+  -- easeInQuad at 0.5 should give 0.25, so x = 0 + (50-0) * 0.25 = 12.5
+  luaunit.assertTrue(result1.x < 25, "easeInQuad should slow start")
+  
+  -- At t=0.75 (middle of second segment with linear)
+  anim.elapsed = 0.75
+  anim._resultDirty = true  -- Mark dirty to force recalculation
+  local result2 = anim:interpolate()
+  -- linear at 0.5 should give 0.5, so x = 50 + (100-50) * 0.5 = 75
+  luaunit.assertAlmostEquals(result2.x, 75, 1)
+end
+
+-- Test findKeyframes method
+function TestKeyframeAnimation:testFindKeyframes()
+  local anim = Animation.keyframes({
+    duration = 1,
+    keyframes = {
+      {at = 0,    values = {x = 0}},
+      {at = 0.25, values = {x = 25}},
+      {at = 0.75, values = {x = 75}},
+      {at = 1,    values = {x = 100}},
+    }
+  })
+  
+  -- Test finding keyframes at different progress values
+  local prev1, next1 = anim:findKeyframes(0.1)
+  luaunit.assertEquals(prev1.at, 0)
+  luaunit.assertEquals(next1.at, 0.25)
+  
+  local prev2, next2 = anim:findKeyframes(0.5)
+  luaunit.assertEquals(prev2.at, 0.25)
+  luaunit.assertEquals(next2.at, 0.75)
+  
+  local prev3, next3 = anim:findKeyframes(0.9)
+  luaunit.assertEquals(prev3.at, 0.75)
+  luaunit.assertEquals(next3.at, 1)
+end
+
+-- Test keyframe animation with update
+function TestKeyframeAnimation:testKeyframeAnimationUpdate()
+  local anim = Animation.keyframes({
+    duration = 1,
+    keyframes = {
+      {at = 0, values = {opacity = 0}},
+      {at = 1, values = {opacity = 1}},
+    }
+  })
+  
+  -- Update halfway through
+  anim:update(0.5)
+  local result = anim:interpolate()
+  
+  luaunit.assertAlmostEquals(result.opacity, 0.5, 0.01)
+  luaunit.assertFalse(anim:update(0)) -- Not complete yet
+  
+  -- Update to completion
+  luaunit.assertTrue(anim:update(0.6)) -- Should complete
+  luaunit.assertEquals(anim:getState(), "completed")
+end
+
+-- Test keyframe animation with callbacks
+function TestKeyframeAnimation:testKeyframeAnimationCallbacks()
+  local startCalled = false
+  local updateCalled = false
+  local completeCalled = false
+  
+  local anim = Animation.keyframes({
+    duration = 1,
+    keyframes = {
+      {at = 0, values = {x = 0}},
+      {at = 1, values = {x = 100}},
+    },
+    onStart = function() startCalled = true end,
+    onUpdate = function() updateCalled = true end,
+    onComplete = function() completeCalled = true end,
+  })
+  
+  anim:update(0.5)
+  luaunit.assertTrue(startCalled)
+  luaunit.assertTrue(updateCalled)
+  luaunit.assertFalse(completeCalled)
+  
+  anim:update(0.6)
+  luaunit.assertTrue(completeCalled)
+end
+
+-- Test missing keyframes (error handling)
+function TestKeyframeAnimation:testMissingKeyframes()
+  -- Should create default keyframes with warning
+  local anim = Animation.keyframes({
+    duration = 1,
+    keyframes = {}
+  })
+  
+  luaunit.assertNotNil(anim)
+  luaunit.assertEquals(#anim.keyframes, 2) -- Should have default start and end
+end
+
+-- Test single keyframe (error handling)
+function TestKeyframeAnimation:testSingleKeyframe()
+  -- Should create default keyframes with warning
+  local anim = Animation.keyframes({
+    duration = 1,
+    keyframes = {
+      {at = 0.5, values = {x = 50}}
+    }
+  })
+  
+  luaunit.assertNotNil(anim)
+  luaunit.assertTrue(#anim.keyframes >= 2) -- Should have at least 2 keyframes
+end
+
+-- Test keyframes without start (at=0)
+function TestKeyframeAnimation:testKeyframesWithoutStart()
+  local anim = Animation.keyframes({
+    duration = 1,
+    keyframes = {
+      {at = 0.5, values = {x = 50}},
+      {at = 1,   values = {x = 100}},
+    }
+  })
+  
+  -- Should auto-add keyframe at 0
+  luaunit.assertEquals(anim.keyframes[1].at, 0)
+  luaunit.assertEquals(anim.keyframes[1].values.x, 50) -- Should copy first keyframe values
+end
+
+-- Test keyframes without end (at=1)
+function TestKeyframeAnimation:testKeyframesWithoutEnd()
+  local anim = Animation.keyframes({
+    duration = 1,
+    keyframes = {
+      {at = 0,   values = {x = 0}},
+      {at = 0.5, values = {x = 50}},
+    }
+  })
+  
+  -- Should auto-add keyframe at 1
+  luaunit.assertEquals(anim.keyframes[#anim.keyframes].at, 1)
+  luaunit.assertEquals(anim.keyframes[#anim.keyframes].values.x, 50) -- Should copy last keyframe values
+end
+
+-- Test keyframe with invalid props
+function TestKeyframeAnimation:testInvalidKeyframeProps()
+  -- Should handle gracefully with warnings
+  local anim = Animation.keyframes({
+    duration = 0, -- Invalid
+    keyframes = "not a table" -- Invalid
+  })
+  
+  luaunit.assertNotNil(anim)
+  luaunit.assertEquals(anim.duration, 1) -- Should use default
+end
+
+-- Test complex multi-property keyframes
+function TestKeyframeAnimation:testMultiPropertyKeyframes()
+  local anim = Animation.keyframes({
+    duration = 2,
+    keyframes = {
+      {at = 0,    values = {x = 0,   y = 0,   opacity = 0,   width = 50}},
+      {at = 0.33, values = {x = 100, y = 50,  opacity = 1,   width = 100}},
+      {at = 0.66, values = {x = 200, y = 100, opacity = 1,   width = 150}},
+      {at = 1,    values = {x = 300, y = 150, opacity = 0,   width = 200}},
+    }
+  })
+  
+  -- Test interpolation at 0.5 (middle of second segment)
+  anim.elapsed = 1.0 -- t = 0.5
+  local result = anim:interpolate()
+  
+  luaunit.assertNotNil(result.x)
+  luaunit.assertNotNil(result.y)
+  luaunit.assertNotNil(result.opacity)
+  luaunit.assertNotNil(result.width)
+  
+  -- Should be interpolating between keyframes at 0.33 and 0.66
+  luaunit.assertTrue(result.x > 100 and result.x < 200)
+  luaunit.assertTrue(result.y > 50 and result.y < 100)
+end
+
+-- Test keyframe with easing function (not string)
+function TestKeyframeAnimation:testKeyframeWithEasingFunction()
+  local customEasing = function(t) return t * t end
+  
+  local anim = Animation.keyframes({
+    duration = 1,
+    keyframes = {
+      {at = 0, values = {x = 0},   easing = customEasing},
+      {at = 1, values = {x = 100}},
+    }
+  })
+  
+  anim.elapsed = 0.5
+  local result = anim:interpolate()
+  
+  -- At t=0.5, easing(0.5) = 0.25, so x = 0 + 100 * 0.25 = 25
+  luaunit.assertAlmostEquals(result.x, 25, 1)
+end
+
+-- Test caching behavior with keyframes
+function TestKeyframeAnimation:testKeyframeCaching()
+  local anim = Animation.keyframes({
+    duration = 1,
+    keyframes = {
+      {at = 0, values = {x = 0}},
+      {at = 1, values = {x = 100}},
+    }
+  })
+  
+  anim.elapsed = 0.5
+  local result1 = anim:interpolate()
+  local result2 = anim:interpolate() -- Should return cached result
+  
+  luaunit.assertEquals(result1, result2) -- Should be same table
+end
+
+os.exit(luaunit.LuaUnit.run())