Are there any standard procedures or codes of practice that cover testing and commissioning of PE pipe?

There are many national standards and codes of practice relating to testing and commissioning of PE pipe. The more recent ones take into account the creep characteristics of the material.

The choice of test method depends on the application for which the pipe is to be used, for instance gas and water applications. The following are examples of test methods available. This is not an exhaustive list but covers some of the more commonly used Standards and Guidelines.

EN805:2000 Water supply. Requirements for systems and components outside buildings

UK
Gas:
Institution of Gas Engineers, Recommendations on Transmission and Distribution, IGE/TD/3 Edition 4 "Steel and PE Pipelines for Gas Distribution"
Water:
WRc Polyethylene Pipe Systems Manual: 2002 (3rd edition)
WRc. A Guide to the Pressure testing of Water Supply Pipelines and Sewer Rising Mains. 1999.

Germany
DVGW W400-2 Bau und Prüfung von Wasserverteilungsanlagen

Sweden
VA-Forsk/Svenskt Vatten VAV P78 Anvisningar för täthetsprovning av tryckledningar tillverkade av polyolefiner.
Swedish Water and Wastewater Association April 1997