Run unit tests in parallel (#2222)

Author: aahung

Makefile

@@ -6,7 +6,7 @@ init:
 	pip install -e '.[dev]'
 
 test:
-	pytest --cov samtranslator --cov-report term-missing --cov-fail-under 95 tests/*
+	pytest --cov samtranslator --cov-report term-missing --cov-fail-under 95 -n auto tests/*
 
 test-cov-report:
 	pytest --cov samtranslator --cov-report term-missing --cov-report html --cov-fail-under 95 tests/*

requirements/dev.txt

@@ -2,6 +2,7 @@ coverage~=5.3
 flake8~=3.8.4
 tox~=3.20.1
 pytest-cov~=2.10.1
+pytest-xdist~=1.34.0  # pytest-xdist 2 is not compatible with Python 2.7
 pylint>=1.7.2,<2.0
 pyyaml~=5.4