Update test_activation.py

Author: Routhleck

brainpy/_src/dnn/tests/test_activation.py

@@ -1,7 +1,13 @@
+import platform
+
 from absl.testing import absltest
 from absl.testing import parameterized
 import brainpy as bp
 import brainpy.math as bm
+import pytest
+
+if platform.system() == 'Darwin':
+  pytest.skip('skip Mac OS', allow_module_level=True)
 
 
 class Test_Activation(parameterized.TestCase):