Preparations parallel testing

some minor corrections to allow parallel testing, which is recommended for hypothesis. See !283 (merged)

Why shell=True was removed and log redirection handled explicitly:

The original implementation used shell=True and shell-based output redirection (> logfile). This can introduce subtle issues, especially related to user permissions and environment handling. For example, when using temporary directories, we observed that the subprocess ( ogs) attempted to write logs into a directory owned by a different user (on windows and with container).

By switching to shell=False and explicitly redirecting stdout/stderr to a file via subprocess.Popen(..., stdout=logf), we avoid:

• unpredictable shell behavior or path interpretation,
• permission issues arising from shell-level redirection,
• reliance on the presence of a specific shell (bash, cmd.exe),
• and improve security by avoiding shell invocation altogether.

This change ensures more reliable and platform-consistent execution.