Add specialized environment for tox

Author: rhpvorderman

setup.py

@@ -25,8 +25,6 @@
 import tempfile
 from pathlib import Path
 
-from Cython.Build import cythonize
-
 from setuptools import Extension, find_packages, setup
 from setuptools.command.build_ext import build_ext
 
@@ -65,6 +63,9 @@ def build_extension(self, ext):
                 os.path.join(isa_l_prefix_dir, "lib", "libisal.a")]
 
         if os.getenv("CYTHON_COVERAGE") is not None:
+            # Import cython here so python setup.py can be used without
+            # installing cython.
+            from Cython.Build import cythonize
             # Add cython directives and macros for coverage support.
             cythonized_exts = cythonize(ext, compiler_directives=dict(
                 linetrace=True

tox.ini

@@ -3,6 +3,14 @@
 # python3 interpreter of the user.
 envlist=py3
 [testenv]
+deps=pytest
+passenv=
+    PYTHON_ISAL_LINK_DYNAMIC
+commands =
+    # Create HTML coverage report for humans and xml coverage report for external services.
+    pytest -v tests
+
+[testenv:coverage]
 deps=coverage[toml]
      cython
      pytest