My solution

lib/tree.rb

@@ -1,38 +1,75 @@
 class NoApplesError < StandardError; end
 
-class AppleTree
-  attr_#fill_in :height, :age, :apples, :alive
+class Tree
+  attr_reader :height
+  attr_reader :age
+  attr_reader :apples
+  attr_reader :alive
+  attr_reader :treeAppleColor
 
   def initialize
+      @age = 0
+      @height = 1
+      @apples = Array.new
+      @alive = true
+      @treeAppleColor = "Red"
   end
 
   def age!
+      @age += 1
+
+      self.add_apples
+      self.grow
+
+      if @age >= 50
+          @alive = false
+      end
+  end
+
+  def grow
+      @height += Random.new.rand(1..10)
   end
 
   def add_apples
+      numApples = Random.new.rand(1..20) * @height
+
+      numApples.times do
+          diameter = Random.new.rand(2.0..4.0)
+          apple = Apple.new(@treeAppleColor, diameter)
+          @apples << apple
+      end
   end
 
   def any_apples?
+      return @apples.count > 0
   end
 
   def pick_an_apple!
     raise NoApplesError, "This tree has no apples" unless self.any_apples?
+
+    apple = @apples.delete_at(rand(@apples.length))
+    return apple
   end
 
   def dead?
+      return !@alive
   end
 end
 
 class Fruit
-  def initialize
-    has_seeds = true
-  end
+    attr_reader :has_seeds
+    def initialize
+        @has_seeds = true
+    end
 end
 
-class Apple <
-  attr_reader #what should go here 
+class Apple < Fruit
+  attr_reader :color
+  attr_reader :diameter
 
   def initialize(color, diameter)
+      @color = color
+      @diameter = diameter
   end
 end
 
@@ -61,7 +98,7 @@ def tree_data
       diameter_sum += apple.diameter
     end
 
-    avg_diameter = # It's up to you to calculate the average diameter for this harvest.
+    avg_diameter = diameter_sum / basket.count.to_f
 
     puts "Year #{tree.age} Report"
     puts "Tree height: #{tree.height} feet"
@@ -76,4 +113,4 @@ def tree_data
 end
 
 # Uncomment this line to run the script, but BE SURE to comment it before you try to run your tests!
-# tree_data
+#tree_data

spec/tree_spec.rb

@@ -1,14 +1,102 @@
 require 'rspec'
 require 'tree'
 
-describe 'Tree' do
-  it 'should be a Class' do
-    expect(described_class.is_a? 'Class').to be_true
-  end
+describe Tree do
+
+    it 'should be a Class' do
+        expect(described_class.is_a? Class).to be true
+    end
+
+    it 'should be a newborn when planted' do
+        tree = Tree.new
+
+        expect(tree.age).to eq 0
+    end
+
+    it 'should have zero apples when planted' do
+        tree = Tree.new
+
+        expect(tree.any_apples?).to eq false
+    end
+
+    it 'should be alive when planted' do
+        tree = Tree.new
+
+        expect(tree.dead?).to eq false
+    end
+
+    it 'should age a year' do
+        tree = Tree.new
+        tree.age!
+
+        expect(tree.age).to eq 1
+    end
+
+    it 'should die after 50 years' do
+        tree = Tree.new
+        50.times do tree.age! end
+
+        expect(tree.dead?).to eq true
+    end
+
+    it 'should add at least one apple each times it ages' do
+        tree = Tree.new
+        startApples = tree.apples.count
+        tree.age!
+        endApples = tree.apples.count
+
+        expect(endApples).to be > startApples
+    end
+
+    it 'should decrease by one apple when an apple is picked' do
+        tree = Tree.new
+        tree.age!
+        startApples = tree.apples.count
+        tree.pick_an_apple!
+        endApples = tree.apples.count
+
+        expect(endApples).to eq (startApples-1)
+    end
+
+    it 'should give an apple when one is picked' do
+        tree = Tree.new
+        tree.age!
+        apple = tree.pick_an_apple!
+
+        expect(apple).to be_instance_of(Apple)
+    end
+
+    it 'should grow a positive value each year' do
+        tree = Tree.new
+        startHeight = tree.height
+        tree.age!
+        endHeight = tree.height
+
+        expect(endHeight).to be > startHeight
+    end
 end
 
-describe 'Fruit' do
+describe Fruit do
+    it 'should be a Class' do
+        expect(described_class.is_a?(Class)).to be true
+    end
+
+    it 'should have seeds' do
+        fruit = Fruit.new
+        expect(fruit.has_seeds).to eq true
+    end
 end
 
-describe 'Apple' do
+describe Apple do
+    it 'should be a Class' do
+        expect(described_class.is_a?(Class)).to be true
+    end
+
+    it 'should set the color and diameter properties' do
+        color = "blue"
+        diameter = 25.3
+        apple = Apple.new(color, diameter)
+        expect(apple.color).to eq color
+        expect(apple.diameter).to eq diameter
+    end
 end