**5. Conclusions**

Among the huge number of research and test methods employed in the construction sector, two groups can be distinguished: methods used to reveal the technical truth about materials, elements or building and methods used to simple conformity assessments of products placed on the market. Combining these two purposes (which is often found in standard tests) does not always give the desired results.

Conformity test methods which do not ensure adequate results precision, would be able to increase the assessment risk area so much that the assessment becomes irrational. Use of such methods can also generate undesirable economic, environmental, and social e ffects because of incorrect assessments. Sustainability in the context of test methods means minimizing such e ffects.

Development of test methods should be preceded the determination of the aim. The initial material test should be a model of reality while a routine test should only be a model of a particular aspect of reality simple enough to deliver predictable results.

Trueness of the test results in the context of the actual conditions of the building working life does not go hand in hand with the precision of the tests, so these two aspects should be split between initial (trueness) and routine (precision) tests.

**Author Contributions:** Conceptualization, E.S., A.W.-S., and L.C.; Methodology, E.S.; Formal analysis, E.S.; Investigation, E.S.; Writing—Original Draft Preparation, E.S.; Writing—Review and Editing, E.S., A.W.-S., and L.C.; Visualization, E.S. and A.W.-S.; Supervision, L.C. All authors have read and agree to the published version of the manuscript.

**Funding:** This research was funded by Ministerstwo Nauki i Szkolnictwa Wy ˙zszego (LN-2/2019).

**Acknowledgments:** Special thanks for Artur Piekarczuk for valuable advices.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
