Judges

1 Early in the morning, Jerub-Baal (that is, Gideon) and all his men camped at the spring of Harod. The camp of Midian was north of them in the valley near the hill of Moreh. 2 The LORD said to Gideon, "You have too many men for me to deliver Midian into their hands. In order that Israel may not boast against me that her own strength has saved her, 3 announce now to the people, 'Anyone who trembles with fear may turn back and leave Mount Gilead.' " So twenty-two thousand men left, while ten thousand remained.
Well it is amazing how fast he assembled that many men! But how sad it would be to see more than half of your army leave. At least men are getting braver and going out to fight even if their scared.
4 But the LORD said to Gideon, "There are still too many men. Take them down to the water, and I will sift them for you there. If I say, 'This one shall go with you,' he shall go; but if I say, 'This one shall not go with you,' he shall not go."
5 So Gideon took the men down to the water. There the LORD told him, "Separate those who lap the water with their tongues like a dog from those who kneel down to drink." 6 Three hundred men lapped with their hands to their mouths. All the rest got down on their knees to drink.
7 The LORD said to Gideon, "With the three hundred men that lapped I will save you and give the Midianites into your hands. Let all the other men go, each to his own place." 8 So Gideon sent the rest of the Israelites to their tents but kept the three hundred, who took over the provisions and trumpets of the others.
I think that test at the water was an awareness test, Gideon needed good aware men so that was how God showed him. The ones who lapped with their tongues could look around and were watchful, while the others just relaxed and drank. This is what I think the test was showing, if anyone has different thoughts you can let me know.