Presumably, there are several candidates for a specific position (perhaps they want to be a council member for a city).
You want to give these candidates a test to determine whether they are suitable for this position that they have applied for.
Then that test could be "the test of the candidates".
Presumably... but like Stavroula said, neither have I heard this in English. And besides, the construction of the English phrase is wrong. It should be:
The candidates' test (Note the apostrophe AFTER the 's' which denotes plural possessive)
Questions? Can a moderator please update this so that DL doesn't continue to teach improper/awkward-sounding English?