Food writers are often envied for the wonderful foods they eat in the line of duty, but the tasting and testing is not as exciting as it appears to be. Take, for example, the testing Paula Wolfert did for her new cookbook, ''The Cooking of South-West France'' (Dial Press, Doubleday, $24.95). She tasted 11 cassoulet recipes in one week.
Not that she complains about it. For Ms. Wolfert it was all part of the challenge of searching out the perfect cassoulet, a French casserole dish of meats and dried white beans.
Food purists claim there are as many ways to make cassoulet as there are ways to make Southern fried chicken or New England fish chowder.
So Ms. Wolfert spent five years, off and on, going from French farmhouse to restaurant, from country inn to chateau. She dined in the best cassoulet establishments in Paris and in three towns famous for the dish. She was envied by people at other tables who couldn't believe the sight of a single woman surrounded by huge casseroles.
Her basic assumption was that there were three ''genuine'' versions of cassoulet. But traveling in southwestern France, she found a different story: In Toulouse they add preserved duck or goose and Toulouse sausage; in Castelnaudary the beans are cooked with chunks of pork, ham, sausage, and pork rind. She heard of one town where mutton was used; in another it was partridge.
''I had to find out which regional dish is the authentic one and also which restaurant serves the very best cassoulet in all of France, the ultimate,'' says Ms. Wolfert.
''Andre Daugin, for example, has a recipe for cassoulet using fava beans, which he says are the beans used originally in the recipe, before white beans were even cultivated in France. I had to have it for my book,'' she says.
But the book is not all cassoulet, nor is it all meat and game and techniques for lowering fat content.
There are recipes for seafood and fish, soups and breads, cheeses and chestnuts. She writes about truffles, foie gras, and walnuts, and she tells about the people involved with growing, preparing, and enjoying these things.
If anyone can put new excitement in an old fashioned or little-known cuisine, it's Paula Wolfert. She first wrote two excellent books, one on Mediterranean foods and another on Moroccan food, the first to explain fully those exotic dishes.
Sorting out the regional differences of this rustic, though magnificent, French food was her metier, and one of her practical accomplishments was making lighter dishes ordinarily thought of as heavy and over-rich, such as cassoulet, comfit, and pot-au-feu.
Admitting that some of them, those with duck and goose especially, have even been called greasy, Ms. Wolfert shows how to add fat for flavor in the same way she uses cinammon stick in a fruit compote. The fat goes in to add flavor, then it comes out before the food is served. Her techniques are not just for certain recipes. They can also be used to reduce a certain amount of fat in all meat dishes without losing flavor.
Even if the nuances escape you when it comes to the differences between nouvelle cuisine and regional cookery, you will appreciate the way she gets around the richness of the traditional dishes while retaining the wonderful seasonings and flavors.
This is not a book for the quick cook. It is for the person who will enjoy finding out how these recipes work and why and where they come from.