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+++ b/README.md
@@ -1,9 +1,15 @@
 # data-structures-and-algorithms-python
+
+
 # Challenge Summary
-IT was eady
+Write a function called BinarySearch which takes in 2 parameters: a sorted array and the search key. Without utilizing any of the built-in methods available to your language, return the index of the array’s element that is equal to the search key, or -1 if the element does not exist.
 ## Challenge Description
-I did a tests to a shift array
-## Approach & Efficiency
-TDD
-## Solution
-![Getting Started](dddddddddddd.png)
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+wRITE A FUNCTION WHICH
+TAKES TWO PARAMS SORTED IN ARRAY AND SEARCH KEY AND RETURN INDEX OF ARR ELEMENT WHICH = TO SEARCH KEY OR "-1" IF IT'S NOT EXIST 
+INPUT => [2,4,6,8],6
+OUTPUT => 2
+
+## Solution![Getting Started](ALGO3.png)
+
+
+https://github.com/MsDiala/data-structures-and-algorithms-python/pull/3 
diff --git a/data_structures_and_algorithms/challenges/array_reverse/__pycache__/array_search.cpython-38.pyc b/data_structures_and_algorithms/challenges/array_reverse/__pycache__/array_search.cpython-38.pyc
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diff --git a/data_structures_and_algorithms/challenges/array_reverse/array_search.py b/data_structures_and_algorithms/challenges/array_reverse/array_search.py
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+def binary_search(arr, key):
+  low = 0
+  high = len(arr)
+  while len(arr) > 0:
+    middle = (low+high) // 2
+    if arr[middle] == key:
+      return middle
+    if arr[middle] < key:
+      low= middle
+    if arr[middle] > key:
+      high= middle
+    if middle == 0 or middle == len(arr) - 1:
+      return -1
+  return -1
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diff --git a/tests/challenges/__pycache__/test_array_search.cpython-38-pytest-6.1.2.pyc b/tests/challenges/__pycache__/test_array_search.cpython-38-pytest-6.1.2.pyc
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diff --git a/tests/challenges/test_array_search.py b/tests/challenges/test_array_search.py
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+++ b/tests/challenges/test_array_search.py
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+from data_structures_and_algorithms.challenges.array_reverse.array_search import binary_search
+
+# "Happy Path" cases
+def test_simple():
+   expected = 3
+   actual = binary_search([1,2,3,4,5,6],4)
+   assert actual == expected
+
+def test_original_nums():
+   expected = 2
+   actual = binary_search([4,8,15,16,23,42], 15)
+   assert actual == expected
+
+def test_absence():
+  expected = -1
+  actual = binary_search([11,22,33,44,55,66,77], 90)
+  assert actual == expected
+
+# Expected Failure
+def test_num_in_left():
+  expected = 0
+  actual = binary_search([11,22,33,44,55,66,77,89,100], 11)
+  assert actual == expected
+
+def test_num_in_right():
+  expected = 8
+  actual = binary_search([11,22,33,44,55,66,77,89,100], 100)
+  assert actual == expected
+
+def test_num_in_middle():
+  expected = 4
+  actual = binary_search([11,22,33,44,55,66,77,89,100], 55)
+  assert actual == expected
+
+def test_num_not_in_right():
+  expected = -1
+  actual = binary_search([11,22,33,44,55,66,77,89,100], 101)
+  assert actual == expected
+
+def test_num_not_in_left():
+  expected = -1
+  actual = binary_search([11,22,33,44,55,66,77,89,100], 10)
+  assert actual == expected
+
+
+
+# Edge Cases
+def test_two_element_arr():
+  expected = 1
+  actual = binary_search([10, 34], 34)
+  assert actual == expected
+
+def test_two_element_arr_anbsence():
+  expected = -1
+  actual = binary_search([10, 34], 19)
+  assert actual == expected
+
+def test_empty_array():
+  expected = -1
+  actual = binary_search([], 19)
+  assert actual == expected
+
+def test_empty_array_negative():
+  expected = -1
+  actual = binary_search([], -1)
+  assert actual == expected
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