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Shabbat is meant to bring holiness and serenity into our lives. Making efforts on Shabbat to prepare for the week is showing disrespect for Shabbat. Therefore, the Sages forbade cleaning the house on Shabbat in anticipation of the upcoming week. Dishes may be washed on Shabbat if they will be needed again at some point during the day, but not for use after Shabbat. Nevertheless, if someone never leaves dirty dishes in the sink during the week and feels that leaving a pile of dirty dishes in the sink desecrates Shabbat, one may wash the dishes in honor of Shabbat. Not pots, though. If someone is bothered by dirty pots in the kitchen, the pots should be moved elsewhere.
A person may study for an upcoming test on a Torah subject, since in any case there is a mitzva to study more Torah than usual on Shabbat. However, it is preferable not to study on Shabbat for tests on secular subjects. When necessary, one may be lenient, since secular studies are also intrinsically valuable.
