The phrase "is a testament that" is perfectly correct and usable in written English.
It is often used to suggest that something is evidence of a certain fact or idea. For example, "The fact that she has been working in the same job for 20 years is a testament to her hard work and dedication."
"Fashion is obviously cyclical and Coco is a testament that we're getting back to that a little bit," said Valerie Boster, the bookings editor at Vogue.
In fact, I think our pretty spectacular growth in audience and subscribers is a testament that people actually do want quality.
Now: we're extreme, and don't really even live together, but that fact in itself is a testament that you can do relationships any way you want.
"His life is a testament that public service is a noble calling," Mr. Obama said of the 41st president before tying the blue-and-white ribbon and medal around his neck.
"For a consumer company to be growing 9percentt in this economic environment is a testament that the products are strong and the company is in touch with its customers," Mr. Sacconaghi said.
Yesterday's launch of Spring, a fashion-focused mobile shopping app, is a testament that the mobile commerce space is growing.
"For me, it's a testament that God's really with us," he told me.
It was a testament that the Erdogan government was unaware of the educative function of endowing individuals with rights and liberties and an autonomous will guaranteed by a functioning and independent judicial system.
"He is very loyal and his party was a testament that he never forgets," says Ms. Chambers, referring to a circle of friendship that includes Hamish Bowles of American Vogue, the opera director Patrick Kinmonth and a dozen others.
It's a testament that it continued to grow even after mom and dad and grandma and grandpa joined.
And it's a testament that it's the one platform where even the dueling tribes of parents and non-parents can occasionally connect.
