If my players have plotted a journey which will take 5 days, will they not have to make a Travel roll during the summer (every 6 day)? Thus if they keeps plotting 5 days journeys will they bypass the Travel Tests?

From Loremaster Book, pag 34:

"A Fatigue test must be made for each full or partial number of days shown in the table that the characters travel for"

Emphasis mine.
5 days of travel are a fraction of 6, so they got 1 fatigue test.

I had my players roll at the beginning of the Journey, and make the next test at the beginning of the next interval. Whether it's right or wrong in order, they never escaped a Fatigue test.

Thank you guys.