diff --git a/.github/workflows/python-package.yml b/.github/workflows/python-package.yml
index 71997c6..1534e18 100644
--- a/.github/workflows/python-package.yml
+++ b/.github/workflows/python-package.yml
@@ -1,7 +1,7 @@
 # This workflow will install Python dependencies, run tests and lint with a variety of Python versions
 # For more information see: https://docs.github.com/en/actions/automating-builds-and-tests/building-and-testing-python
 
-name: Python package
+name: Build and Test
 
 on: push
 
diff --git a/.gitignore b/.gitignore
index 692b66b..1db8f7e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -90,5 +90,4 @@ ENV/
 
 /tests/tests.config
 /tests/creds.json
-/travis.secrets.tar.gz
 /.venv
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index 38b68c3..0000000
--- a/.travis.yml
+++ /dev/null
@@ -1,18 +0,0 @@
-language: python
-cache: pip
-python:
-- '2.7'
-- '3.7.9'
-- '3.8'
-- '3.9'
-install:
-- pip install -U pip
-- pip uninstall -y six
-- pip install six>=1.12.0
-- if [[ $TRAVIS_PYTHON_VERSION == 2.6* ]]; then pip install --only-binary -e .; else
-  pip install --prefer-binary -e .; fi
-script: python setup.py test
-before_install:
-- openssl aes-256-cbc -K $encrypted_efe1688938da_key -iv $encrypted_efe1688938da_iv
-  -in travis.secrets.tar.gz.enc -out travis.secrets.tar.gz -d
-- tar xvzf travis.secrets.tar.gz
diff --git a/MANIFEST.in b/MANIFEST.in
index 792ff63..ada6128 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -10,3 +10,4 @@ recursive-include tests *.example
 recursive-include tests *.json
 recursive-include tests *.py
 exclude tests/creds.json
+exclude tests/tests.config
diff --git a/README.rst b/README.rst
index 07280fd..7840919 100644
--- a/README.rst
+++ b/README.rst
@@ -4,8 +4,8 @@ gspread-dataframe
 .. image:: https://badge.fury.io/py/gspread-dataframe.svg
     :target: https://badge.fury.io/py/gspread-dataframe
 
-.. image:: https://app.travis-ci.com/robin900/gspread-dataframe.svg?branch=master
-    :target: https://travis-ci.com/robin900/gspread-dataframe
+.. image:: https://github.com/robin900/gspread-dataframe/actions/workflows/python-package.yml/badge.svg?branch=master
+    :target: https://github.com/robin900/gspread-dataframe/actions/workflows/python-package.yml
 
 .. image:: https://img.shields.io/pypi/dm/gspread-dataframe.svg
     :target: https://pypi.org/project/gspread-dataframe
@@ -72,7 +72,8 @@ Installation
 Requirements
 ~~~~~~~~~~~~
 
-* Python 2.7, 3+
+* Python 3 only, for releases 4.0.0 and later
+* Python 2.7 and 3 for releases prior to 4.0.0
 * gspread (>=3.0.0; to use older versions of gspread, use gspread-dataframe releases of 2.1.1 or earlier)
 * Pandas >= 0.24.0
 
diff --git a/VERSION b/VERSION
index fcdb2e1..c9d9681 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-4.0.0
+4.0.0b1
diff --git a/gspread_dataframe.py b/gspread_dataframe.py
index 7505f18..b39b210 100644
--- a/gspread_dataframe.py
+++ b/gspread_dataframe.py
@@ -17,7 +17,6 @@
 import logging
 import re
 from numbers import Real
-from six import string_types, ensure_text
 
 try:
     from collections.abc import defaultdict
@@ -70,11 +69,9 @@ def _cellrepr(value, allow_formulas, string_escaping):
         return ""
     if isinstance(value, Real):
         return value
-    if not isinstance(value, string_types):
+    if not isinstance(value, str):
         value = str(value)
 
-    value = ensure_text(value, encoding='utf-8')
-
     if (not allow_formulas) and value.startswith("="):
         return "'%s" % value
     else:
diff --git a/pyproject.toml b/pyproject.toml
new file mode 100644
index 0000000..7dfaab4
--- /dev/null
+++ b/pyproject.toml
@@ -0,0 +1,62 @@
+[build-system]
+requires = ["setuptools", "wheel"]
+build-backend = "setuptools.build_meta" 
+
+[project]
+name = "gspread-dataframe" 
+dynamic = ["version"]
+description = "Read/write gspread worksheets using pandas DataFrames"
+readme = "README.rst"
+requires-python = ">=3.0"
+license = { file = "LICENSE" }
+keywords = ['spreadsheets', 'google-spreadsheets', 'pandas', 'dataframe']
+authors = [{ name = "Robin Thomas", email = "rthomas900@gmail.com" }]
+maintainers = [{ name = "Robin Thomas", email = "rthomas900@gmail.com" }]
+
+classifiers = [
+  "Development Status :: 5 - Production/Stable",
+  "Intended Audience :: Developers",
+  "Intended Audience :: Science/Research",
+  "Topic :: Office/Business :: Financial :: Spreadsheet",
+  "Topic :: Software Development :: Libraries :: Python Modules",
+  "License :: OSI Approved :: MIT License",
+  "Programming Language :: Python :: 3"
+]
+
+dependencies = ["gspread>=3.0.0", "pandas>=0.24.0"] 
+
+[project.optional-dependencies]
+dev = [
+"gitchangelog",
+"Sphinx",
+"Sphinx-PyPI-upload3",
+"twine",
+"pytest",
+"oauth2client"
+]
+
+test = [
+"pytest",
+"oauth2client",
+"pandas",
+"tox"
+]
+
+[project.urls]
+"Homepage" = "https://github.com/robin900/gspread-dataframe"
+"Bug Reports" = "https://github.com/robin900/gspread-dataframe/issues"
+"Source" = "https://github.com/robin900/gspread-dataframe/"
+
+[tool.setuptools.dynamic]
+version = {file = "VERSION"}
+
+[tool.coverage.report]
+fail_under = 90
+show_missing = true
+exclude_lines = [
+    'pragma: no cover',
+    '\.\.\.',
+    'if TYPE_CHECKING:',
+    "if __name__ == '__main__':",
+]
+
diff --git a/requirements-dev.txt b/requirements-dev.txt
deleted file mode 100644
index d436ea5..0000000
--- a/requirements-dev.txt
+++ /dev/null
@@ -1,6 +0,0 @@
-oauth2client
-gitchangelog
-Sphinx
-Sphinx-PyPI-upload3
-twine
-wheel
diff --git a/setup.cfg b/setup.cfg
deleted file mode 100644
index d6443c8..0000000
--- a/setup.cfg
+++ /dev/null
@@ -1,15 +0,0 @@
-[bdist_wheel]
-universal = 1
-
-[metadata]
-license_file=LICENSE
-
-[build_sphinx]
-source-dir = docs
-build-dir  = docs/_build
-all_files  = 1
-
-[upload_sphinx]
-upload-dir = docs/_build/html
-repository = https://pypi.python.org/pypi
-
diff --git a/setup.py b/setup.py
deleted file mode 100644
index e0d3773..0000000
--- a/setup.py
+++ /dev/null
@@ -1,52 +0,0 @@
-try:
-    from setuptools import setup
-except ImportError:
-    from distutils.core import setup
-
-import os.path
-import sys
-
-PY3 = sys.version_info >= (3, 0)
-
-with open(os.path.join(os.path.dirname(__file__), 'VERSION'), 'rb') as f:
-    VERSION = f.read()
-    if PY3:
-        VERSION = VERSION.decode('utf8')
-    VERSION = VERSION.strip()
-
-with open(os.path.join(os.path.dirname(__file__), 'README.rst'), 'rb') as f:
-    long_description = f.read()
-    if PY3:
-        long_description = long_description.decode('utf8')
-
-setup(
-    name='gspread-dataframe',
-    version=VERSION,
-    py_modules=['gspread_dataframe'],
-    test_suite='tests',
-    install_requires=[
-        'gspread>=3.0.0', 
-        'pandas>=0.24.0',
-        'six>=1.12.0'
-        ],
-    tests_require=['oauth2client'] + ([] if PY3 else ['mock']),
-    description='Read/write gspread worksheets using pandas DataFrames',
-    long_description=long_description,
-    author='Robin Thomas',
-    author_email='rthomas900@gmail.com',
-    license='MIT',
-    url='https://github.com/robin900/gspread-dataframe',
-    keywords=['spreadsheets', 'google-spreadsheets', 'pandas', 'dataframe'],
-    classifiers=[
-        "Programming Language :: Python",
-        "Programming Language :: Python :: 3",
-        "License :: OSI Approved :: MIT License",
-        "Operating System :: OS Independent",
-        "Development Status :: 5 - Production/Stable",
-        "Intended Audience :: Developers",
-        "Intended Audience :: Science/Research",
-        "Topic :: Office/Business :: Financial :: Spreadsheet",
-        "Topic :: Software Development :: Libraries :: Python Modules"
-        ],
-    zip_safe=True
-)
diff --git a/tests/gspread_dataframe_test.py b/tests/gspread_dataframe_test.py
index 76dde58..d94bb44 100644
--- a/tests/gspread_dataframe_test.py
+++ b/tests/gspread_dataframe_test.py
@@ -172,9 +172,10 @@ def test_skiprows(self):
         self.assertEqual(len(df), 6)
 
     def test_squeeze(self):
-        df = get_as_dataframe(self.sheet, usecols=[0], squeeze=True)
-        self.assertTrue(isinstance(df, pd.Series))
-        self.assertEqual(len(df), 9)
+        if pd.__version__ < '2.0.0':
+            df = get_as_dataframe(self.sheet, usecols=[0], squeeze=True)
+            self.assertTrue(isinstance(df, pd.Series))
+            self.assertEqual(len(df), 9)
 
     def test_converters_datetime(self):
         df = get_as_dataframe(
@@ -218,7 +219,7 @@ def test_parse_dates_custom_parser(self):
         df = get_as_dataframe(
             self.sheet,
             parse_dates=[4],
-            date_parser=lambda x: datetime.strptime(x, "%Y-%m-%d") if x is not np.nan else None
+            date_format="%Y-%m-%d"
         )
         self.assertEqual(df["Date Column"][0], datetime(2017, 3, 4))
 
@@ -289,6 +290,11 @@ def test_write_basic(self):
             CELL_LIST_STRINGIFIED, value_input_option="USER_ENTERED"
         )
 
+    def test_write_empty_df_no_updates(self):
+        df = pd.DataFrame.from_records([])
+        set_with_dataframe(self.sheet, df)
+        self.sheet.update_cells.assert_not_called()
+
     def test_include_index_false(self):
         df = get_as_dataframe(self.sheet, na_filter=False)
         df_index = df.set_index("Thingy")
diff --git a/tox.ini b/tox.ini
new file mode 100644
index 0000000..3a4ed0f
--- /dev/null
+++ b/tox.ini
@@ -0,0 +1,25 @@
+[tox]
+env_list =
+    3.8
+    3.13
+minversion = 4.24.2
+
+[testenv]
+description = run the tests with pytest
+package = wheel
+wheel_build_env = .pkg
+deps =
+    pytest>=6
+    coverage
+    oauth2client
+    !3.8: pandas>=2.0.0
+    3.8: pandas<2.0.0
+commands = 
+  coverage erase
+  coverage run -m pytest {tty:--color=yes} tests/gspread_dataframe_test.py tests/gspread_dataframe_integration.py {posargs}
+  coverage report --omit='tests/*'
+
+[gh-actions]
+python = 
+  3.8: py38
+  3.13: py313
diff --git a/travis.secrets.tar.gz.enc b/travis.secrets.tar.gz.enc
deleted file mode 100644
index 13be0aa..0000000
Binary files a/travis.secrets.tar.gz.enc and /dev/null differ