Adding check.py to tests, rather than a simple generic assert on number of wheels

test/01_basic/check.py

@@ -0,0 +1,9 @@
+import glob
+import subprocess
+import sys
+
+build_identifiers = subprocess.check_output([sys.executable, '-m', 'cibuildwheel', '--print-build-identifiers'], universal_newlines=True).strip().split('\n')
+expected_identifiers = build_identifiers
+built_wheels = glob.glob('wheelhouse/*.whl')
+
+assert len(built_wheels) == len(expected_identifiers)