It is something of a milestone when the National Association of Realtors, long the foe of open housing bills, agrees with HUD Secretary Samuel Pierce on a bill to spend $3 million in federal money for testing compliance with the existing fair housing law. It's important, however, to look at the fine print. Mr. Pierce had to make substantial concessions to the Realtors. The question before Congress is whether it's worth enacting the concessions into law in order to get federal money for testing.

The most dubious, we think, is the proviso that federally funded testing organizations could only respond to independently generated complaints. They could not send out their black and white testers -- people who pose as buyers with identical resources -- to companies against which no complaint had independently been made. Another restriction: testers would have to approach the same salesman, not just the same company.

These restrictions are bad policy. It would be better if the program authorized what the fair housing organizations call "systemic testing" (sending out testers more or less at random, to see who's complying and who's not), and if testers were not required to seek out the same salesman. There is the further danger that the courts will take these restrictions on federally funded testing and apply them to testing that is not federally funded. Several dozen organizations around the country operate testing programs now, and some will probably prefer to continue their current programs rather than accept the limitations agreed to by Mr. Pierce and the Realtors. They should be free to make this choice.

Underneath the sometimes bitter differences between the Realtors and the fair housing testing organizations is a disagreement about how the housing market works. Does the market these days, as many Realtors think, give almost anyone walking into a real estate office his choice? Or are many blacks and others deterred, as fair housing testers think, from even considering alternatives that should be open to them? One way to find out is to tighten up on testing. If the Realtors are right, what can they have to fear from a program that fairly tests their premise? It's heartening to see the Realtors endorse a federally funded testing program. Some testing, even if limited, is better than none. But the Pierce-NAR version is only half a loaf, and Congress should be careful not to limit testing programs that do not receive federal money.