[unittest] supported condititonal testing based on env var (#1701)

polish code

colossalai/testing/pytest_wrapper.py

@@ -0,0 +1,17 @@
+import pytest
+import os
+
+
+def run_on_environment_flag(name: str):
+    """
+    Conditionally run a test based on the environment variable. If this environment variable is set
+    to 1, this test will be executed. Otherwise, this test is skipped. The environment variable is default to 0.
+    """
+    assert isinstance(name, str)
+    flag = os.environ.get(name.upper(), '0')
+
+    reason = f'Environment varialbe {name} is {flag}'
+    if flag == '1':
+        return pytest.mark.skipif(False, reason=reason)
+    else:
+        return pytest.mark.skipif(True, reason=reason)