Update requirements.txt

requirements.txt

@@ -5,4 +5,5 @@ tqdm~=4.45.0
 dataclasses~=0.7
 scipy~=1.4.1
 matplotlib~=3.2.1
-setuptools~=46.1.3
\ No newline at end of file
+setuptools~=46.1.3
+pytest==5.3.5