Test pilots try to push the envelope.

试飞员尝试挑战极限。

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To test this possibility, Bieniasz's team engineered an unrelated mouse retrovirus coated with the envelope protein that would have allowed the ancient chimpanzee virus to slip into cells.

为了检验这种可能性，Bieniasz的团队设计了毫不相关的涂有包膜蛋白的老鼠反转录病毒，这种病毒容许黑猩猩病毒进入细胞。

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For instance, a good test assertion is a JUnit test that returns true if and only if the SOAP envelope returned by a Web service is identical to a pre-defined XML document.

例如，一个较好的测试断言为JUnit测试，即当且仅当Web服务返回的SOAP信封与预定义的XML文档完全相同时，返回true。

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Many visioneers champion free markets, less government, fewer regulations and profits for those who test the technological envelope.

CNN: A pioneer in space and on Earth

So far, the company has built a one-eighth-size prototype to test its design, which consists of a carbon-fibre keel, an envelope made from modern composite materials, half-a-dozen engines, a passenger compartment, and a specially lightened crane.

ECONOMIST: Pushing the envelope