The phrase "stress condition" is accurate as it relates to the negative impact the environment can have on the material or equipment in question. Thus, negative impact is written as "stress" while the environment in which the stress occurs is called the "condition". The term "condition" here would mean the area in which the material is tested and how it is tested.
"Test conditions" relates to the environment in which the materials is being tested. This may or may not involve stressing the materials.
When using field specific language, or nomenclature, certain phrases will appear strange. This is simply a result of using the terminology best suited to the field.
南アフリカ 
