diff --git a/tests/test_turnbull.py b/tests/test_turnbull.py
new file mode 100644
index 0000000..f3884f0
--- /dev/null
+++ b/tests/test_turnbull.py
@@ -0,0 +1,52 @@
+#   scipy-yli: Helpful SciPy utilities and recipes
+#   Copyright © 2022–2023  Lee Yingtong Li (RunasSudo)
+#
+#   This program is free software: you can redistribute it and/or modify
+#   it under the terms of the GNU Affero General Public License as published by
+#   the Free Software Foundation, either version 3 of the License, or
+#   (at your option) any later version.
+#
+#   This program is distributed in the hope that it will be useful,
+#   but WITHOUT ANY WARRANTY; without even the implied warranty of
+#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#   GNU Affero General Public License for more details.
+#
+#   You should have received a copy of the GNU Affero General Public License
+#   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+from pytest import approx
+
+import pandas as pd
+
+import yli
+
+def test_turnbull_simple():
+	"""Compare yli.turnbull for simple example"""
+	
+	df = pd.DataFrame({
+		'Time_L': [0.5, 1, 3, 5],
+		'Time_R': [2.5, 2, 4, 6]
+	})
+	
+	xpoints, ypoints = yli.survival.calc_survfunc_turnbull(df['Time_L'], df['Time_R'])
+	
+	assert xpoints[0] == 0
+	assert ypoints[0] == 1
+	
+	assert xpoints[1] == approx(1.5)
+	assert ypoints[1] == 1
+	
+	assert xpoints[2] == approx(1.5)
+	assert ypoints[2] == 0.5
+	
+	assert xpoints[3] == approx(3.5)
+	assert ypoints[3] == 0.5
+	
+	assert xpoints[4] == approx(3.5)
+	assert ypoints[4] == 0.25
+	
+	assert xpoints[5] == approx(5.5)
+	assert ypoints[5] == 0.25
+	
+	assert xpoints[6] == approx(5.5)
+	assert ypoints[6] == 0