diff --git a/pytest_localstack/compat.py b/pytest_localstack/compat.py
new file mode 100644
index 0000000..64c92f5
--- /dev/null
+++ b/pytest_localstack/compat.py
@@ -0,0 +1,8 @@
+"""Handle compatibility issues between Python 2 and Python 3."""
+
+import six
+
+if six.PY3:
+    from unittest import mock
+else:
+    import mock  # noqa
diff --git a/pytest_localstack/utils.py b/pytest_localstack/utils.py
new file mode 100644
index 0000000..84c6a74
--- /dev/null
+++ b/pytest_localstack/utils.py
@@ -0,0 +1,25 @@
+"""Misc utilities."""
+import six
+
+
+def check_no_proxy():
+    """Raise warnings about improperly set no_proxy env var."""
+    proxy_settings = six.moves.urllib.request.getproxies()
+    if 'http' not in proxy_settings and 'https' not in proxy_settings:
+        return
+    if 'no' not in proxy_settings:
+        raise UserWarning(
+            "You have proxy settings, but no_proxy isn't set. "
+            "If you try to connect to localhost (i.e. like pytest-localstack does) "
+            "it's going to try to go through the proxy and fail. "
+            "Set the no_proxy environment variable to something like "
+            "'localhost,127.0.0.1' (and maybe add your local network as well? ;D )"
+        )
+    if '127.0.0.1' not in proxy_settings['no']:
+        raise UserWarning(
+            "You have proxy settings (including no_proxy) set, "
+            "but no_proxy doens't contain '127.0.0.1'. "
+            "This is needed for Localstack. "
+            "Please set the no_proxy environment variable to something like "
+            "'localhost,127.0.0.1' (and maybe add your local network as well? ;D )"
+        )
diff --git a/tests/test_dummy.py b/tests/test_dummy.py
deleted file mode 100644
index 5687270..0000000
--- a/tests/test_dummy.py
+++ /dev/null
@@ -1,7 +0,0 @@
-"""Dummy tests"""
-import pytest_localstack
-
-
-def test_dummy():
-    """Dummy to make sure tests work."""
-    assert pytest_localstack.__version__ == '0.1.0-dev'
diff --git a/tests/unit/__init__.py b/tests/unit/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/unit/test_utils.py b/tests/unit/test_utils.py
new file mode 100644
index 0000000..d19c049
--- /dev/null
+++ b/tests/unit/test_utils.py
@@ -0,0 +1,52 @@
+"""Unit tests for pytest_localstack.utils."""
+import os
+
+import pytest
+from hypothesis import (
+    given,
+    strategies as st,
+)
+
+from pytest_localstack import (
+    compat,
+    utils,
+)
+
+
+def _get_env_var(name):
+    return os.environ.get(name) or os.environ.get(name.upper(), '')
+
+
+@given(
+    test_environ=st.fixed_dictionaries({
+        'http_proxy': st.sampled_from(['', 'http://proxy:3128']),
+        'https_proxy': st.sampled_from(['', 'http://proxy:3128']),
+        'HTTP_PROXY': st.sampled_from(['', 'http://proxy:3128']),
+        'HTTPS_PROXY': st.sampled_from(['', 'http://proxy:3128']),
+        'no_proxy': st.sampled_from(['', 'localhost,127.0.0.1', 'localhost', 'foobar']),
+        'NO_PROXY': st.sampled_from(['', 'localhost,127.0.0.1', 'localhost', 'foobar']),
+    })
+)
+def test_check_no_proxy(test_environ):
+    """Test pytest_localstack.utils.check_no_proxy."""
+    with compat.mock.patch.dict(os.environ):
+        # mock.patch.dict can't delete keys.
+        # Patch os.environ manually.
+        for key, value in test_environ.items():
+            if value:
+                os.environ[key] = value
+            else:
+                os.environ.pop(key, None)
+
+        has_http_proxy = bool(_get_env_var('http_proxy'))
+        has_https_proxy = bool(_get_env_var('https_proxy'))
+        good_no_proxy = '127.0.0.1' in _get_env_var('no_proxy')
+
+        if has_http_proxy or has_https_proxy:
+            if good_no_proxy:
+                utils.check_no_proxy()
+            else:
+                with pytest.raises(UserWarning):
+                    utils.check_no_proxy()
+        else:
+            utils.check_no_proxy()