diff --git a/Collatz.py b/Collatz.py
index f4279c0..454549d 100755
--- a/Collatz.py
+++ b/Collatz.py
@@ -23,6 +23,7 @@ def __init__(self,size):
     
     def write(self,i,val):
         try:
+            assert i > 0
             if (self.cache[i-1] > 0): #then already wrote val
                 return
         
@@ -31,19 +32,20 @@ def write(self,i,val):
         except IndexError:
             pass
     
-        
+   
     # -------------
     #  read_cache
     # -------------
     
     def read(self,i):
         try:
+            assert i > 0
             return self.cache[i-1]
       
         except IndexError:
             return 0
     
-    def size():
+    def size(self):
         return len(self.cache)
                 
 
@@ -93,23 +95,33 @@ def collatz_eval (i, j) :
     assert i <= k
 
     #initialize a cold cache
+    cache = Cache(k)
+    assert cache.size() == k
+
     while( k >= i):
-        result=cycle_length(k)
+        result=cycle_length(k,cache)
         if (c_len < result) :
             c_len=result
         k-=1
-    assert c_len >0
+    assert c_len > 0
     return c_len
 
 # -------------
 # cycle_length
 # -------------
 
-def cycle_length (n) :
+def cycle_length (n,cache) :
     assert n > 0
     c = 1
     m = n
+    
     while n > 1 :
+        x = cache.read(n)
+        if (x > 0):
+            c = (c + x) - 1
+            assert c > 0
+            cache.write(m,c)
+            return c
 
         if (n % 2) == 0 :
             n = (n >> 1)
@@ -118,6 +130,7 @@ def cycle_length (n) :
             n = n + (n>>1) + 1
             c += 2
     assert c > 0
+    cache.write(m,c)
     return c
 
 # -------------
diff --git a/mas5774-TestCollatz.py b/mas5774-TestCollatz.py
index 9ef6234..f9b3b23 100755
--- a/mas5774-TestCollatz.py
+++ b/mas5774-TestCollatz.py
@@ -20,13 +20,43 @@
 from io       import StringIO
 from unittest import main, TestCase
 
-from Collatz import collatz_read, collatz_eval, collatz_print, collatz_solve
+from Collatz import Cache, collatz_read, collatz_eval, collatz_print, collatz_solve
 
 # -----------
 # TestCollatz
 # -----------
 
 class TestCollatz (TestCase) :
+    # ----
+    # Cache
+    # ----
+
+    def test_cache_1 (self) :
+        c = Cache(10)
+        self.assertEqual(10, c.size())
+
+
+    def test_cache_2 (self) :
+        c = Cache(10)
+        c.write(2, 10)
+        self.assertEqual(c.read(2), 10)
+
+
+    def test_cache_3 (self) :
+        c = Cache(0)
+        self.assertEqual(c.size(), 0)
+
+
+    def test_cache_4 (self) :
+        c = Cache(10)
+        c.write(1, 100)
+        self.assertEqual(c.read(1), 100)
+
+
+    def test_cache_5 (self) :
+        c = Cache(10)
+        self.assertEqual(c.read(3), 0)
+
     # ----
     # read
     # ----
@@ -111,8 +141,21 @@ def test_eval_9 (self) :
     def test_eval_10 (self) :
         v = collatz_eval(20, 20)
         self.assertEqual(v, 8)
+
+    def test_eval_11 (self) :
         w = collatz_eval(19, 19)
         self.assertEqual(w, 21)
+    def test_eval_12 (self) :
+        w = collatz_eval(1, 999999)
+        self.assertEqual(w, 525)
+
+    def test_eval_13 (self) :
+        w = collatz_eval(999999, 1)
+        self.assertEqual(w, 525)
+
+    def test_eval_14 (self) :
+        w = collatz_eval(999999, 999999)
+        self.assertEqual(w, 259)
 
     # -----
     # print