diff --git a/u2/list_ops_test.py b/u2/list_ops_test.py
index 7bf6ae5..1a66e31 100644
--- a/u2/list_ops_test.py
+++ b/u2/list_ops_test.py
@@ -7,6 +7,7 @@ def append(list1, list2):
         result.append(element)
     return result
 
+
 def concat(lists):
     result = []
 
@@ -15,3 +16,27 @@ def concat(lists):
             result.append(element)
     return result
 
+
+def filter(function, seq):
+    result = []
+
+    for element in seq:
+        if function(element):
+            result.append(element)
+    return result
+
+
+def lenght(seq):
+    count = 0
+
+    for element in seq:
+        count += 1
+    return count
+
+
+def map(function, seq):
+    result = []
+
+    for element in seq:
+        result.append(function(element))
+    return result