ISO 13849 validation: When do you need to test in addition to analysis?

In the scope of ISO 13849-2, you must perform testing when analysis alone is not conclusive. It stipulates that testing is is always complementary to analysis and \[testing\] is often necessary. No specific guidelines are given when testing is neccessary.

Generally, is is always recommended to perform at least a nominal amount of physical testing, not only to verify the functionality of safety functions, but also to verify that there are, for example, no cabling issues. Due to analysis generally being unable to identify some types of cabling issues which appear in physical reality (i.e. being inconclusive), it is often mandated to perform testing indirectly.

However, this neither means you have to perform 100% physical tests on all safety function aspects, nor does it mandate to perform any specific tests.

This testing-optional strategy is in stark contrast to IEC 62061, which specifies to always perform testing after analysis, even though the. The reason for this difference is that ISO 13849-2 is prep

Source: ISO 13849-2, section 6. Validation by testing, particularly 6.1 General