Americans' generosity is being tested this holiday season in response to the earthquake in Soviet Armenia and to the needy at home.

By at least one measure - United Way's projection for the year of 6 percent to 7 percent growth - donations nationwide appear to have increased.Charities in many communities say contributions of money, clothing, toys and food are at least keeping pace with last year and should pick up this week before Christmas.

But in other cities, contributions have dropped, hampered by cold weather, a shortage of bell ringers, shopping malls that banish fund-raisers from entrances, weak local economies, or even a drain on givers from campaign contributions earlier this year.

Efforts to aid the victims of the earthquake in Soviet Armenia appear to be having an impact on domestic giving in some cities, but not in others, say spokesmen for the Salvation Army, American Red Cross, Volunteers of America, United Way, food banks and other charities.

In Massachusetts, with an Armenian population estimated at more than 60,000, most charity officials said it is too early to tell whether that has cut into local giving.

But at the American Red Cross, the tragedy appears to have prompted an across-the-board increase in giving, said Philip Schuyler, manager of operations, planning and development in Boston.

"The response has been the greatest I've ever seen in 18 years," he said. "They're giving to both situations - the homeless here, the hungry in Armenia."

Among the nation's biggest cities, collections were reported up in New York, Chicago, and Atlanta but down in Los Angeles. In the Midwest, Indianapolis, Kansas City, Mo., and St. Louis reported healthy donations, while Minneapolis, Detroit and Iowa's cities were having a more difficult time. And in the West, Phoenix and Tucson, Ariz., showed drops, while Denver and Salt Lake charities said their contributions were on target.

In Dallas, the Dallas Morning News Charities reported its drive was ahead of last year's pace, but the Salvation Army said its cash donations are down, part of the continuing impact of the oil bust.

In Minneapolis, contributions to both Catholic Charities and the Salvation Army are flagging.

The presidential campaign drain has been a problem, said fund-raisers in Southern California, where Salvation Army donations for the eight-county region are running 15 percent behind their 1987 rate.

"The fact of the matter is that we usually suffer every four years when there's an election," said Russell Prince, the army's director of development in Southern California. "We got hurt in '84, but we've seen it this year more than ever. They've gotten more sophisticated in their direct mail fund-raising techniques and it's hurt us this year more than ever."