The test used to measure the sensitivity of a penetrant to water contamination is called:

The appropriate test used to measure the sensitivity of a penetrant to water contamination is known as the water tolerance test. This test is designed to evaluate how the penetrant performs in the presence of water, ensuring that the penetrant will not be adversely affected by moisture or water exposure during the inspection process.

Understanding the sensitivity of a penetrant to water is essential, as any contamination can negatively impact the effectiveness of the penetrant in detecting defects. The water tolerance test helps in determining the minimum conditions under which the penetrant can still function effectively, ensuring reliable results when performing non-destructive testing.

The other options refer to tests that either do not exist as formal methods in the context of liquid penetrant testing or do not specifically measure the penetrant's ability to tolerate water. The water resistance test could imply how well a penetrant holds up against water, but it lacks the specific context of measuring contamination sensitivity, making it less accurate than the water tolerance test. Similarly, the water penetration test and the water solubility test do not directly concern the assessment of a penetrant's sensitivity to contamination by water, thereby solidifying the water tolerance test as the correct and definitive assessment in this regard.