The first test was at Mt. Sinai. Fifty days after crossing the Red Sea, the people camped at the foot of the mountain. Moses went up to meet God and receive the covenant for Israel. After forty days, Moses returned from Mt. Sinai, saw the children of Israel worshiping the golden calf and became so angry that he broke the stone tablets. Forty days after Weeks/Pentecost was the 17th of Tammuz (June/July).
It came to pass, as soon as he came nigh unto the camp, that he saw the calf, and the dancing: and Moses' anger waxed hot, and he cast the tables out of his hands, and brake them beneath the mount (Exodus 32:19).
Jewish Calendar
Nisan - Tishri
The second test was at Kadesh Barnea. One year after God's miraculous deliverance from Egypt, twelve spies were sent to explore the land forty days. The Hebrews had a choice to follow God's plan and take the Promised Land or believe the evil report and rebel against God. Because of a lack of faith, ten spies rebelled against God, discouraged the people and they all wander in the wilderness forty years. The Kadesh Barnea rebellion occurred on the 9th of Av (July/August).
Caleb stilled the people before Moses, and said, Let us go up at once, and possess it [the Promised Land]; for we are well able to overcome it. But the men that went up with him said, We are not able to go up against the people; for they are stronger than we (Numbers 13:30-31).