diff --git a/tests/core/lib/test_base.py b/tests/core/lib/test_base.py
new file mode 100644
index 000000000..ec167fcfd
--- /dev/null
+++ b/tests/core/lib/test_base.py
@@ -0,0 +1,59 @@
+from unittest.mock import patch
+
+from nettacker.core.lib.base import BaseEngine, BaseLibrary
+
+
+class ConcreteEngine(BaseEngine):
+    """Concrete subclass for testing abstract BaseEngine methods."""
+
+    library = BaseLibrary
+
+
+class TestBaseLibrary:
+    def test_base_library_client_is_none(self):
+        assert BaseLibrary.client is None
+
+    def test_base_library_brute_force_returns_none(self):
+        library = BaseLibrary()
+        assert library.brute_force() is None
+
+
+class TestBaseEngineFilterLargeContent:
+    def setup_method(self):
+        self.engine = ConcreteEngine()
+
+    def test_short_content_returned_unchanged(self):
+        content = "short string"
+        assert self.engine.filter_large_content(content) == content
+
+    def test_exactly_150_chars_returned_unchanged(self):
+        content = "x" * 150
+        assert self.engine.filter_large_content(content) == content
+
+    @patch("nettacker.core.lib.base._", return_value=" ... [filtered]")
+    def test_long_content_truncated_at_word_boundary(self, mock_messages):
+        content = "a" * 155 + " " + "b" * 50
+        result = self.engine.filter_large_content(content)
+        assert result.endswith(" ... [filtered]")
+        assert len(result) < len(content)
+
+    @patch("nettacker.core.lib.base._", return_value=" ... [filtered]")
+    def test_long_content_with_space_after_filter_rate(self, mock_messages):
+        content = "a" * 155 + " rest of content"
+        result = self.engine.filter_large_content(content)
+        assert result.endswith(" ... [filtered]")
+
+    def test_long_content_no_space_returns_full(self):
+        content = "a" * 300
+        result = self.engine.filter_large_content(content)
+        assert result == content
+
+    def test_custom_filter_rate(self):
+        content = "a" * 50
+        assert self.engine.filter_large_content(content, filter_rate=50) == content
+
+    @patch("nettacker.core.lib.base._", return_value=" ... [filtered]")
+    def test_custom_filter_rate_truncates(self, mock_messages):
+        content = "a" * 10 + " " + "b" * 50
+        result = self.engine.filter_large_content(content, filter_rate=10)
+        assert result.endswith(" ... [filtered]")
diff --git a/tests/core/lib/test_ftp.py b/tests/core/lib/test_ftp.py
new file mode 100644
index 000000000..3096552d7
--- /dev/null
+++ b/tests/core/lib/test_ftp.py
@@ -0,0 +1,104 @@
+import ftplib
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+from nettacker.core.lib.ftp import FtpEngine, FtpLibrary
+from nettacker.core.lib.ftps import FtpsEngine, FtpsLibrary
+
+HOST = "ftp.example.com"
+PORT = 21
+USERNAME = "admin"
+PASSWORD = "secret"  # noqa: S105
+TIMEOUT = 10
+
+
+class TestFtpLibrary:
+    @patch.object(FtpLibrary, "client")
+    def test_brute_force_success(self, mock_ftp_cls):
+        mock_conn = MagicMock()
+        mock_ftp_cls.return_value = mock_conn
+
+        library = FtpLibrary()
+        result = library.brute_force(
+            host=HOST, port=PORT, username=USERNAME, password=PASSWORD, timeout=TIMEOUT
+        )
+
+        mock_ftp_cls.assert_called_once_with(timeout=TIMEOUT)
+        mock_conn.connect.assert_called_once_with(HOST, PORT)
+        mock_conn.login.assert_called_once_with(USERNAME, PASSWORD)
+        mock_conn.close.assert_called_once()
+
+        assert result == {
+            "host": HOST,
+            "port": PORT,
+            "username": USERNAME,
+            "password": PASSWORD,
+        }
+
+    @patch.object(FtpLibrary, "client")
+    def test_brute_force_login_failure(self, mock_ftp_cls):
+        mock_conn = MagicMock()
+        mock_ftp_cls.return_value = mock_conn
+        mock_conn.login.side_effect = ftplib.error_perm("530 Login incorrect")
+
+        library = FtpLibrary()
+        with pytest.raises(ftplib.error_perm):
+            library.brute_force(
+                host=HOST, port=PORT, username=USERNAME, password=PASSWORD, timeout=TIMEOUT
+            )
+
+    @patch.object(FtpLibrary, "client")
+    def test_brute_force_connection_refused(self, mock_ftp_cls):
+        mock_conn = MagicMock()
+        mock_ftp_cls.return_value = mock_conn
+        mock_conn.connect.side_effect = ConnectionRefusedError("Connection refused")
+
+        library = FtpLibrary()
+        with pytest.raises(ConnectionRefusedError):
+            library.brute_force(
+                host=HOST, port=PORT, username=USERNAME, password=PASSWORD, timeout=TIMEOUT
+            )
+
+
+class TestFtpEngine:
+    def test_engine_uses_ftp_library(self):
+        assert FtpEngine.library is FtpLibrary
+
+
+class TestFtpsLibrary:
+    def test_inherits_from_ftp_library(self):
+        assert issubclass(FtpsLibrary, FtpLibrary)
+
+    def test_uses_ftp_tls_client(self):
+        assert FtpsLibrary.client is ftplib.FTP_TLS
+
+    @patch.object(FtpsLibrary, "client")
+    def test_brute_force_success(self, mock_ftps_cls):
+        mock_conn = MagicMock()
+        mock_ftps_cls.return_value = mock_conn
+
+        library = FtpsLibrary()
+        result = library.brute_force(
+            host=HOST, port=PORT, username=USERNAME, password=PASSWORD, timeout=TIMEOUT
+        )
+
+        mock_ftps_cls.assert_called_once_with(timeout=TIMEOUT)
+        mock_conn.connect.assert_called_once_with(HOST, PORT)
+        mock_conn.login.assert_called_once_with(USERNAME, PASSWORD)
+        mock_conn.close.assert_called_once()
+
+        assert result == {
+            "host": HOST,
+            "port": PORT,
+            "username": USERNAME,
+            "password": PASSWORD,
+        }
+
+
+class TestFtpsEngine:
+    def test_inherits_from_ftp_engine(self):
+        assert issubclass(FtpsEngine, FtpEngine)
+
+    def test_engine_uses_ftps_library(self):
+        assert FtpsEngine.library is FtpsLibrary
diff --git a/tests/core/lib/test_pop3.py b/tests/core/lib/test_pop3.py
new file mode 100644
index 000000000..7d870431b
--- /dev/null
+++ b/tests/core/lib/test_pop3.py
@@ -0,0 +1,102 @@
+import poplib
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+from nettacker.core.lib.pop3 import Pop3Engine, Pop3Library
+from nettacker.core.lib.pop3s import Pop3sEngine, Pop3sLibrary
+
+HOST = "mail.example.com"
+PORT = 110
+USERNAME = "user@example.com"
+PASSWORD = "secret"  # noqa: S105
+TIMEOUT = 10
+
+
+class TestPop3Library:
+    @patch.object(Pop3Library, "client")
+    def test_brute_force_success(self, mock_pop3_cls):
+        mock_conn = MagicMock()
+        mock_pop3_cls.return_value = mock_conn
+
+        library = Pop3Library()
+        result = library.brute_force(
+            host=HOST, port=PORT, username=USERNAME, password=PASSWORD, timeout=TIMEOUT
+        )
+
+        mock_pop3_cls.assert_called_once_with(HOST, port=PORT, timeout=TIMEOUT)
+        mock_conn.user.assert_called_once_with(USERNAME)
+        mock_conn.pass_.assert_called_once_with(PASSWORD)
+        mock_conn.quit.assert_called_once()
+
+        assert result == {
+            "host": HOST,
+            "port": PORT,
+            "username": USERNAME,
+            "password": PASSWORD,
+        }
+
+    @patch.object(Pop3Library, "client")
+    def test_brute_force_auth_error(self, mock_pop3_cls):
+        mock_conn = MagicMock()
+        mock_pop3_cls.return_value = mock_conn
+        mock_conn.pass_.side_effect = poplib.error_proto("-ERR Authentication failed")
+
+        library = Pop3Library()
+        with pytest.raises(poplib.error_proto):
+            library.brute_force(
+                host=HOST, port=PORT, username=USERNAME, password=PASSWORD, timeout=TIMEOUT
+            )
+
+    @patch.object(Pop3Library, "client")
+    def test_brute_force_connection_refused(self, mock_pop3_cls):
+        mock_pop3_cls.side_effect = ConnectionRefusedError("Connection refused")
+
+        library = Pop3Library()
+        with pytest.raises(ConnectionRefusedError):
+            library.brute_force(
+                host=HOST, port=PORT, username=USERNAME, password=PASSWORD, timeout=TIMEOUT
+            )
+
+
+class TestPop3Engine:
+    def test_engine_uses_pop3_library(self):
+        assert Pop3Engine.library is Pop3Library
+
+
+class TestPop3sLibrary:
+    def test_inherits_from_pop3_library(self):
+        assert issubclass(Pop3sLibrary, Pop3Library)
+
+    def test_uses_pop3_ssl_client(self):
+        assert Pop3sLibrary.client is poplib.POP3_SSL
+
+    @patch.object(Pop3sLibrary, "client")
+    def test_brute_force_success(self, mock_pop3s_cls):
+        mock_conn = MagicMock()
+        mock_pop3s_cls.return_value = mock_conn
+
+        library = Pop3sLibrary()
+        result = library.brute_force(
+            host=HOST, port=995, username=USERNAME, password=PASSWORD, timeout=TIMEOUT
+        )
+
+        mock_pop3s_cls.assert_called_once_with(HOST, port=995, timeout=TIMEOUT)
+        mock_conn.user.assert_called_once_with(USERNAME)
+        mock_conn.pass_.assert_called_once_with(PASSWORD)
+        mock_conn.quit.assert_called_once()
+
+        assert result == {
+            "host": HOST,
+            "port": 995,
+            "username": USERNAME,
+            "password": PASSWORD,
+        }
+
+
+class TestPop3sEngine:
+    def test_inherits_from_pop3_engine(self):
+        assert issubclass(Pop3sEngine, Pop3Engine)
+
+    def test_engine_uses_pop3s_library(self):
+        assert Pop3sEngine.library is Pop3sLibrary
diff --git a/tests/core/lib/test_smb.py b/tests/core/lib/test_smb.py
index e5b7898ce..b2948e426 100644
--- a/tests/core/lib/test_smb.py
+++ b/tests/core/lib/test_smb.py
@@ -23,7 +23,7 @@ def test_brute_force_password(self, mock_smb_connection):
         HOST = "dc-01"
         PORT = 445
         USERNAME = "Administrator"
-        PASSWORD = "Password@123"
+        PASSWORD = "Password@123"  # noqa: S105
 
         mock_smb_connection.return_value = MockSmbConnectionObject(
             HOST, remoteHost=HOST, sess_port=PORT
diff --git a/tests/core/lib/test_smtp.py b/tests/core/lib/test_smtp.py
new file mode 100644
index 000000000..942481b64
--- /dev/null
+++ b/tests/core/lib/test_smtp.py
@@ -0,0 +1,123 @@
+import smtplib
+from unittest.mock import MagicMock, call, patch
+
+import pytest
+
+from nettacker.core.lib.smtp import SmtpEngine, SmtpLibrary
+from nettacker.core.lib.smtps import SmtpsEngine, SmtpsLibrary
+
+HOST = "smtp.example.com"
+PORT = 25
+USERNAME = "user@example.com"
+PASSWORD = "secret"  # noqa: S105
+TIMEOUT = 10
+
+
+class TestSmtpLibrary:
+    @patch.object(SmtpLibrary, "client")
+    def test_brute_force_success(self, mock_smtp_cls):
+        mock_conn = MagicMock()
+        mock_smtp_cls.return_value = mock_conn
+
+        library = SmtpLibrary()
+        result = library.brute_force(
+            host=HOST, port=PORT, username=USERNAME, password=PASSWORD, timeout=TIMEOUT
+        )
+
+        mock_smtp_cls.assert_called_once_with(HOST, PORT, timeout=TIMEOUT)
+        mock_conn.login.assert_called_once_with(USERNAME, PASSWORD)
+        mock_conn.close.assert_called_once()
+
+        assert result == {
+            "host": HOST,
+            "port": PORT,
+            "username": USERNAME,
+            "password": PASSWORD,
+        }
+
+    @patch.object(SmtpLibrary, "client")
+    def test_brute_force_auth_error(self, mock_smtp_cls):
+        mock_conn = MagicMock()
+        mock_smtp_cls.return_value = mock_conn
+        mock_conn.login.side_effect = smtplib.SMTPAuthenticationError(
+            535, b"Authentication failed"
+        )
+
+        library = SmtpLibrary()
+        with pytest.raises(smtplib.SMTPAuthenticationError):
+            library.brute_force(
+                host=HOST, port=PORT, username=USERNAME, password=PASSWORD, timeout=TIMEOUT
+            )
+
+    @patch.object(SmtpLibrary, "client")
+    def test_brute_force_connection_refused(self, mock_smtp_cls):
+        mock_smtp_cls.side_effect = ConnectionRefusedError("Connection refused")
+
+        library = SmtpLibrary()
+        with pytest.raises(ConnectionRefusedError):
+            library.brute_force(
+                host=HOST, port=PORT, username=USERNAME, password=PASSWORD, timeout=TIMEOUT
+            )
+
+
+class TestSmtpEngine:
+    def test_engine_uses_smtp_library(self):
+        assert SmtpEngine.library is SmtpLibrary
+
+
+class TestSmtpsLibrary:
+    @patch.object(SmtpsLibrary, "client")
+    def test_brute_force_success(self, mock_smtp_cls):
+        mock_conn = MagicMock()
+        mock_smtp_cls.return_value = mock_conn
+
+        library = SmtpsLibrary()
+        result = library.brute_force(
+            host=HOST, port=587, username=USERNAME, password=PASSWORD, timeout=TIMEOUT
+        )
+
+        mock_smtp_cls.assert_called_once_with(HOST, 587, timeout=TIMEOUT)
+        mock_conn.starttls.assert_called_once()
+        mock_conn.login.assert_called_once_with(USERNAME, PASSWORD)
+        mock_conn.close.assert_called_once()
+
+        assert result == {
+            "host": HOST,
+            "port": 587,
+            "username": USERNAME,
+            "password": PASSWORD,
+        }
+
+    @patch.object(SmtpsLibrary, "client")
+    def test_starttls_called_before_login(self, mock_smtp_cls):
+        mock_conn = MagicMock()
+        mock_smtp_cls.return_value = mock_conn
+
+        manager = MagicMock()
+        mock_conn.starttls = manager.starttls
+        mock_conn.login = manager.login
+
+        library = SmtpsLibrary()
+        library.brute_force(
+            host=HOST, port=587, username=USERNAME, password=PASSWORD, timeout=TIMEOUT
+        )
+
+        expected_calls = [call.starttls(), call.login(USERNAME, PASSWORD)]
+        assert manager.mock_calls[:2] == expected_calls
+
+    @patch.object(SmtpsLibrary, "client")
+    def test_brute_force_starttls_failure(self, mock_smtp_cls):
+        mock_conn = MagicMock()
+        mock_smtp_cls.return_value = mock_conn
+        mock_conn.starttls.side_effect = smtplib.SMTPException("STARTTLS extension not supported")
+
+        library = SmtpsLibrary()
+        with pytest.raises(smtplib.SMTPException):
+            library.brute_force(
+                host=HOST, port=587, username=USERNAME, password=PASSWORD, timeout=TIMEOUT
+            )
+
+
+class TestSmtpsEngine:
+    def test_engine_uses_smtps_library(self):
+        assert SmtpsEngine.library is SmtpsLibrary
diff --git a/tests/core/lib/test_ssh.py b/tests/core/lib/test_ssh.py
new file mode 100644
index 000000000..e6d4506d7
--- /dev/null
+++ b/tests/core/lib/test_ssh.py
@@ -0,0 +1,92 @@
+from unittest.mock import MagicMock, patch
+
+import pytest
+from paramiko import AutoAddPolicy
+from paramiko.auth_strategy import NoneAuth, Password
+
+from nettacker.core.lib.ssh import SshEngine, SshLibrary
+
+HOST = "ssh.example.com"
+PORT = 22
+USERNAME = "admin"
+PASSWORD = "secret"  # noqa: S105
+
+
+class TestSshLibrary:
+    @patch.object(SshLibrary, "client")
+    def test_brute_force_with_password(self, mock_ssh_cls):
+        mock_conn = MagicMock()
+        mock_ssh_cls.return_value = mock_conn
+
+        library = SshLibrary()
+        result = library.brute_force(host=HOST, port=PORT, username=USERNAME, password=PASSWORD)
+
+        mock_ssh_cls.assert_called_once()
+        mock_conn.set_missing_host_key_policy.assert_called_once()
+
+        connect_kwargs = mock_conn.connect.call_args
+        assert connect_kwargs.kwargs["hostname"] == HOST
+        assert connect_kwargs.kwargs["port"] == PORT
+        assert isinstance(connect_kwargs.kwargs["auth_strategy"], Password)
+
+        assert result == {
+            "host": HOST,
+            "port": PORT,
+            "username": USERNAME,
+            "password": PASSWORD,
+        }
+
+    @patch.object(SshLibrary, "client")
+    def test_brute_force_without_password(self, mock_ssh_cls):
+        mock_conn = MagicMock()
+        mock_ssh_cls.return_value = mock_conn
+
+        library = SshLibrary()
+        result = library.brute_force(host=HOST, port=PORT, username=USERNAME, password="")
+
+        connect_kwargs = mock_conn.connect.call_args
+        assert isinstance(connect_kwargs.kwargs["auth_strategy"], NoneAuth)
+
+        assert result == {
+            "host": HOST,
+            "port": PORT,
+            "username": USERNAME,
+            "password": "",
+        }
+
+    @patch.object(SshLibrary, "client")
+    def test_brute_force_none_password_uses_none_auth(self, mock_ssh_cls):
+        mock_conn = MagicMock()
+        mock_ssh_cls.return_value = mock_conn
+
+        library = SshLibrary()
+        result = library.brute_force(host=HOST, port=PORT, username=USERNAME, password=None)
+
+        connect_kwargs = mock_conn.connect.call_args
+        assert isinstance(connect_kwargs.kwargs["auth_strategy"], NoneAuth)
+
+    @patch.object(SshLibrary, "client")
+    def test_brute_force_connection_refused(self, mock_ssh_cls):
+        mock_conn = MagicMock()
+        mock_ssh_cls.return_value = mock_conn
+        mock_conn.connect.side_effect = ConnectionRefusedError("Connection refused")
+
+        library = SshLibrary()
+        with pytest.raises(ConnectionRefusedError):
+            library.brute_force(host=HOST, port=PORT, username=USERNAME, password=PASSWORD)
+
+    @patch.object(SshLibrary, "client")
+    def test_brute_force_sets_auto_add_policy(self, mock_ssh_cls):
+        mock_conn = MagicMock()
+        mock_ssh_cls.return_value = mock_conn
+
+        library = SshLibrary()
+        library.brute_force(host=HOST, port=PORT, username=USERNAME, password=PASSWORD)
+
+        policy_arg = mock_conn.set_missing_host_key_policy.call_args[0][0]
+        assert isinstance(policy_arg, AutoAddPolicy)
+
+
+class TestSshEngine:
+    def test_engine_uses_ssh_library(self):
+        assert SshEngine.library is SshLibrary
diff --git a/tests/core/lib/test_telnet.py b/tests/core/lib/test_telnet.py
new file mode 100644
index 000000000..08ce1a849
--- /dev/null
+++ b/tests/core/lib/test_telnet.py
@@ -0,0 +1,62 @@
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+from nettacker.core.lib.telnet import TelnetEngine, TelnetLibrary
+
+HOST = "192.168.1.1"
+PORT = 23
+USERNAME = "admin"
+PASSWORD = "secret"  # noqa: S105
+TIMEOUT = 10
+
+
+class TestTelnetLibrary:
+    @patch.object(TelnetLibrary, "client")
+    def test_brute_force_success(self, mock_telnet_cls):
+        mock_conn = MagicMock()
+        mock_telnet_cls.return_value = mock_conn
+
+        library = TelnetLibrary()
+        result = library.brute_force(
+            host=HOST, port=PORT, username=USERNAME, password=PASSWORD, timeout=TIMEOUT
+        )
+
+        mock_telnet_cls.assert_called_once_with(HOST, PORT, TIMEOUT)
+        mock_conn.read_until.assert_any_call(b"login: ")
+        mock_conn.write.assert_any_call(USERNAME.encode("utf-8") + b"\n")
+        mock_conn.read_until.assert_any_call(b"Password: ")
+        mock_conn.write.assert_any_call(PASSWORD.encode("utf-8") + b"\n")
+        mock_conn.close.assert_called_once()
+
+        assert result == {
+            "host": HOST,
+            "port": PORT,
+            "username": USERNAME,
+            "password": PASSWORD,
+        }
+
+    @patch.object(TelnetLibrary, "client")
+    def test_brute_force_connection_refused(self, mock_telnet_cls):
+        mock_telnet_cls.side_effect = ConnectionRefusedError("Connection refused")
+
+        library = TelnetLibrary()
+        with pytest.raises(ConnectionRefusedError):
+            library.brute_force(
+                host=HOST, port=PORT, username=USERNAME, password=PASSWORD, timeout=TIMEOUT
+            )
+
+    @patch.object(TelnetLibrary, "client")
+    def test_brute_force_timeout(self, mock_telnet_cls):
+        mock_telnet_cls.side_effect = TimeoutError("Connection timed out")
+
+        library = TelnetLibrary()
+        with pytest.raises(TimeoutError):
+            library.brute_force(
+                host=HOST, port=PORT, username=USERNAME, password=PASSWORD, timeout=TIMEOUT
+            )
+
+
+class TestTelnetEngine:
+    def test_engine_uses_telnet_library(self):
+        assert TelnetEngine.library is TelnetLibrary
diff --git a/tests/core/test_socks_proxy.py b/tests/core/test_socks_proxy.py
new file mode 100644
index 000000000..cd009c1c0
--- /dev/null
+++ b/tests/core/test_socks_proxy.py
@@ -0,0 +1,105 @@
+import socket
+import sys
+from unittest.mock import MagicMock, patch
+
+from nettacker.core.socks_proxy import getaddrinfo, set_socks_proxy
+
+
+class TestGetaddrinfo:
+    def test_returns_correct_tuple_format(self):
+        result = getaddrinfo("127.0.0.1", 8080)
+        assert result == [(socket.AF_INET, socket.SOCK_STREAM, 6, "", ("127.0.0.1", 8080))]
+
+    def test_with_hostname(self):
+        result = getaddrinfo("example.com", 443)
+        assert result == [(socket.AF_INET, socket.SOCK_STREAM, 6, "", ("example.com", 443))]
+
+    def test_returns_single_element_list(self):
+        result = getaddrinfo("10.0.0.1", 1080)
+        assert len(result) == 1
+
+    def test_extra_args_ignored(self):
+        result = getaddrinfo("host", 80, "extra1", "extra2")
+        assert result == [(socket.AF_INET, socket.SOCK_STREAM, 6, "", ("host", 80))]
+
+
+class TestSetSocksProxyNone:
+    def test_returns_stdlib_socket_when_no_proxy(self):
+        sock, addr_info = set_socks_proxy(None)
+        assert sock is socket.socket
+        assert addr_info is socket.getaddrinfo
+
+    def test_returns_stdlib_socket_when_empty_string(self):
+        sock, addr_info = set_socks_proxy("")
+        assert sock is socket.socket
+        assert addr_info is socket.getaddrinfo
+
+
+class TestSetSocksProxySocks5:
+    def test_socks5_no_auth(self):
+        mock_socks = MagicMock()
+        mock_socks.SOCKS5 = 2
+        mock_socks.SOCKS4 = 1
+
+        with patch.dict(sys.modules, {"socks": mock_socks}):
+            sock, addr_info = set_socks_proxy("socks5://127.0.0.1:1080")
+
+        mock_socks.set_default_proxy.assert_called_once_with(
+            2,  # SOCKS5
+            "127.0.0.1",
+            1080,
+        )
+        assert sock is mock_socks.socksocket
+        assert addr_info is getaddrinfo
+
+    def test_socks5_with_auth(self):
+        mock_socks = MagicMock()
+        mock_socks.SOCKS5 = 2
+        mock_socks.SOCKS4 = 1
+
+        with patch.dict(sys.modules, {"socks": mock_socks}):
+            sock, addr_info = set_socks_proxy("socks5://myuser:mypass@proxy.example.com:9050")
+
+        mock_socks.set_default_proxy.assert_called_once_with(
+            2,  # SOCKS5
+            "proxy.example.com",
+            9050,
+            username="myuser",
+            password="mypass",
+        )
+        assert sock is mock_socks.socksocket
+        assert addr_info is getaddrinfo
+
+
+class TestSetSocksProxySocks4:
+    def test_socks4_no_auth(self):
+        mock_socks = MagicMock()
+        mock_socks.SOCKS5 = 2
+        mock_socks.SOCKS4 = 1
+
+        with patch.dict(sys.modules, {"socks": mock_socks}):
+            sock, addr_info = set_socks_proxy("socks4://10.0.0.1:1080")
+
+        mock_socks.set_default_proxy.assert_called_once_with(
+            1,  # SOCKS4
+            "10.0.0.1",
+            1080,
+        )
+        assert sock is mock_socks.socksocket
+        assert addr_info is getaddrinfo
+
+    def test_no_scheme_defaults_to_socks4(self):
+        mock_socks = MagicMock()
+        mock_socks.SOCKS5 = 2
+        mock_socks.SOCKS4 = 1
+
+        with patch.dict(sys.modules, {"socks": mock_socks}):
+            sock, addr_info = set_socks_proxy("192.168.1.1:1080")
+
+        mock_socks.set_default_proxy.assert_called_once_with(
+            1,  # SOCKS4
+            "192.168.1.1",
+            1080,
+        )
+        assert sock is mock_socks.socksocket
+        assert addr_info is getaddrinfo