diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index d09842c..5908b8f 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -12,7 +12,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v5
         with:
-          python-version: "3.13"
+          python-version: "3.12"
 
       - name: Install dependencies
         run: |
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..3d0c924
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,31 @@
+# Python
+__pycache__/
+*.pyc
+*.pyo
+*.pyd
+*.so
+
+# Virtual environments
+venv/
+env/
+.venv/
+
+# IDE
+.vscode/
+.idea/
+*.swp
+*.swo
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Testing
+.pytest_cache/
+.coverage
+htmlcov/
+
+# Project-specific
+*.log
+temp/
+tmp/
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..d564eb6
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2025 Elizaveta Menshikova
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/src/bin_search.py b/src/bin_search.py
index 713abfc..c55ccbb 100644
--- a/src/bin_search.py
+++ b/src/bin_search.py
@@ -1,6 +1,10 @@
 def binSearch(xs: list[int], x: int):
+    if x not in xs:
+        raise ValueError("такого элемента нет")
+    if xs != sorted(xs):
+        raise ValueError("Массив не отсортирован")
     left, right = 0, len(xs) - 1
-    while left < right:
+    while left <= right:
         mid = (left + right) // 2
         if xs[mid] == x:
             return mid
diff --git a/test/test_bin_searh.py b/test/test_bin_searh.py
index d18d85b..9ad49cd 100644
--- a/test/test_bin_searh.py
+++ b/test/test_bin_searh.py
@@ -1,3 +1,4 @@
+import pytest
 from src.bin_search import binSearch
 
 
@@ -11,3 +12,13 @@ def test_start():
 
 def test_not_in_list():
     assert binSearch([1, 2, 3, 4], 5) == -1
+
+
+def test_unsorted():
+    with pytest.raises(ValueError, match="Массив не отсортирован"):
+        binSearch([8, 3, 6, 1], 6)
+
+
+def test_unsorted():
+    with pytest.raises(ValueError, match="такого элемента нет"):
+        binSearch([1, 2, 3], 9)
diff --git a/test/test_checksum.py b/test/test_checksum.py
index f64a64c..d7d7a3f 100644
--- a/test/test_checksum.py
+++ b/test/test_checksum.py
@@ -1,3 +1,4 @@
+import pytest
 from src.checksum import modulo11Checksum