diff --git a/tests/test_users.py b/tests/test_users.py
index 0d8d423..bc07951 100644
--- a/tests/test_users.py
+++ b/tests/test_users.py
@@ -91,93 +91,127 @@ def undefined_settings(mocker, datadir):
     return datadir
 
 
+class ProcessMock:
+    """Mock subprocess.Popen"""
+
+    def __init__(self, args, **kwargs):
+        self.args = args
+        self.kwargs = kwargs
+
+    def communicate():
+        return (b"NEW_HASHED", None)
+
+    returncode = 0
+
+
+@pytest.fixture
+def mock_subprocess_popen(mocker):
+    mock = mocker.patch("subprocess.Popen", autospec=True, return_value=ProcessMock)
+    return mock
+
+
 ##  TESTS  ######################################################
 
 
-def test_get_users_unauthorized(client, some_users):
+def test_get_users_unauthorized(client, some_users, mock_subprocess_popen):
     response = client.get("/users")
     assert response.status_code == 401
 
 
-def test_get_some_users(authorized_client, some_users):
+def test_get_some_users(authorized_client, some_users, mock_subprocess_popen):
     response = authorized_client.get("/users")
     assert response.status_code == 200
     assert response.json == ["user1", "user2", "user3"]
 
 
-def test_get_one_user(authorized_client, one_user):
+def test_get_one_user(authorized_client, one_user, mock_subprocess_popen):
     response = authorized_client.get("/users")
     assert response.status_code == 200
     assert response.json == ["user1"]
 
 
-def test_get_no_users(authorized_client, no_users):
+def test_get_no_users(authorized_client, no_users, mock_subprocess_popen):
     response = authorized_client.get("/users")
     assert response.status_code == 200
     assert response.json == []
 
 
-def test_get_undefined_users(authorized_client, undefined_settings):
+def test_get_undefined_users(
+    authorized_client, undefined_settings, mock_subprocess_popen
+):
     response = authorized_client.get("/users")
     assert response.status_code == 200
     assert response.json == []
 
 
-def test_post_users_unauthorized(client, some_users):
+def test_post_users_unauthorized(client, some_users, mock_subprocess_popen):
     response = client.post("/users")
     assert response.status_code == 401
 
 
-def test_post_one_user(authorized_client, one_user):
+def test_post_one_user(authorized_client, one_user, mock_subprocess_popen):
     response = authorized_client.post(
         "/users", json={"username": "user4", "password": "password"}
     )
     assert response.status_code == 201
-    assert read_json(one_user / "one_user.json")["users"][1]["username"] == "user4"
+    assert read_json(one_user / "one_user.json")["users"] == [
+        {
+            "username": "user1",
+            "hashedPassword": "HASHED_PASSWORD_1",
+            "sshKeys": ["ssh-rsa KEY user1@pc"],
+        },
+        {
+            "username": "user4",
+            "hashedPassword": "NEW_HASHED",
+        },
+    ]
 
 
-def test_post_without_username(authorized_client, one_user):
+def test_post_without_username(authorized_client, one_user, mock_subprocess_popen):
     response = authorized_client.post("/users", json={"password": "password"})
     assert response.status_code == 400
 
 
-def test_post_without_password(authorized_client, one_user):
+def test_post_without_password(authorized_client, one_user, mock_subprocess_popen):
     response = authorized_client.post("/users", json={"username": "user4"})
     assert response.status_code == 400
 
 
-def test_post_without_username_and_password(authorized_client, one_user):
+def test_post_without_username_and_password(
+    authorized_client, one_user, mock_subprocess_popen
+):
     response = authorized_client.post("/users", json={})
     assert response.status_code == 400
 
 
 @pytest.mark.parametrize("username", invalid_usernames)
-def test_post_system_user(authorized_client, one_user, username):
+def test_post_system_user(authorized_client, one_user, mock_subprocess_popen, username):
     response = authorized_client.post(
         "/users", json={"username": username, "password": "password"}
     )
     assert response.status_code == 409
 
 
-def test_post_existing_user(authorized_client, one_user):
+def test_post_existing_user(authorized_client, one_user, mock_subprocess_popen):
     response = authorized_client.post(
         "/users", json={"username": "user1", "password": "password"}
     )
     assert response.status_code == 409
 
 
-def test_post_user_to_undefined_users(authorized_client, undefined_settings):
+def test_post_user_to_undefined_users(
+    authorized_client, undefined_settings, mock_subprocess_popen
+):
     response = authorized_client.post(
         "/users", json={"username": "user4", "password": "password"}
     )
     assert response.status_code == 201
-    assert (
-        read_json(undefined_settings / "undefined.json")["users"][0]["username"]
-        == "user4"
-    )
+    assert read_json(undefined_settings / "undefined.json")["users"] == [
+        {"username": "user4", "hashedPassword": "NEW_HASHED"}
+    ]
 
 
-def test_post_very_long_username(authorized_client, one_user):
+def test_post_very_long_username(authorized_client, one_user, mock_subprocess_popen):
     response = authorized_client.post(
         "/users", json={"username": "a" * 100, "password": "password"}
     )
@@ -185,24 +219,26 @@ def test_post_very_long_username(authorized_client, one_user):
 
 
 @pytest.mark.parametrize("username", ["", "1", "фыр", "user1@", "№:%##$^&@$&^()_"])
-def test_post_invalid_username(authorized_client, one_user, username):
+def test_post_invalid_username(
+    authorized_client, one_user, mock_subprocess_popen, username
+):
     response = authorized_client.post(
         "/users", json={"username": username, "password": "password"}
     )
     assert response.status_code == 400
 
 
-def test_delete_user_unauthorized(client, some_users):
+def test_delete_user_unauthorized(client, some_users, mock_subprocess_popen):
     response = client.delete("/users/user1")
     assert response.status_code == 401
 
 
-def test_delete_user_not_found(authorized_client, some_users):
+def test_delete_user_not_found(authorized_client, some_users, mock_subprocess_popen):
     response = authorized_client.delete("/users/user4")
     assert response.status_code == 404
 
 
-def test_delete_user(authorized_client, some_users):
+def test_delete_user(authorized_client, some_users, mock_subprocess_popen):
     response = authorized_client.delete("/users/user1")
     assert response.status_code == 200
     assert read_json(some_users / "some_users.json")["users"] == [
@@ -212,21 +248,23 @@ def test_delete_user(authorized_client, some_users):
 
 
 @pytest.mark.parametrize("username", invalid_usernames)
-def test_delete_system_user(authorized_client, some_users, username):
+def test_delete_system_user(
+    authorized_client, some_users, mock_subprocess_popen, username
+):
     response = authorized_client.delete("/users/" + username)
     assert response.status_code == 400 or response.status_code == 404
 
 
-def test_delete_main_user(authorized_client, some_users):
+def test_delete_main_user(authorized_client, some_users, mock_subprocess_popen):
     response = authorized_client.delete("/users/tester")
     assert response.status_code == 400
 
 
-def test_delete_without_argument(authorized_client, some_users):
+def test_delete_without_argument(authorized_client, some_users, mock_subprocess_popen):
     response = authorized_client.delete("/users/")
     assert response.status_code == 404
 
 
-def test_delete_just_delete(authorized_client, some_users):
+def test_delete_just_delete(authorized_client, some_users, mock_subprocess_popen):
     response = authorized_client.delete("/users")
     assert response.status_code == 405