A brief, informal test or quiz, often used in educational settings. The prefix 豆 (まめ) adds a sense of smallness or lightness.
授業の最初に豆テストをします。
We'll have a short quiz at the beginning of class.
Compound of 豆 (まめ, 'bean; small') and テスト (test). The prefix 豆 is used here to indicate something small or minor.