Since the main test runner is HTML based, having a browser open is a necessity.

由于主要的测试运行器是基于HTML的，因此打开浏览器是必须的。

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Having the ability to test the application environment — not just the application — is a necessity.

拥有测试应用程序环境—而不仅仅是应用程序—的能力是必不可少的。

youdao

Necessity and speciality for synthetic test for asymmetrical current breaking are explained.

阐述了进行非对称电流开断合成试验的必要性和特殊性。

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He leafed through the pharmaceutical bible, the Physicians' Desk Reference, and selected 300 drugs to test, culling only those for which fast-onset was a necessity, including medicine for migraines (Imitrex), allergies (Claritin) and depression (Prozac).

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