The verse of Shemot 16:4 tells that HaShem will cause bread to rain (come down) from heaven to (humble; Devarim 8:16 and) test the people whether or not they will walk in His Torah.
The literal rendering of a part of this verse is that the people had to gather a word a day in its day.
Devarim 8:3 refers to this and tells that HaShem did so in order to teach that we don't live by bread alone, but by all (words) that comes forth from the mouth of HaShem.
The text shows the way HaShem tested the people (by gathering the Mahn), and its goal (to see if they would walk in His Torah); but how where the people tested by this act, and in which way did the gathering of Mahn represents the goal or that which was tested?