CSS argument for "if first child is"

I need a CSS selector for inside a div开发者_如何转开发 but I want it to only select the element if its the first element of a specific class inside that div.

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As your title implies "if first child is": div > .test:first-child will select the first child of any <div> if it has the class test.

But if the first child of the <div> doesn't have the class test, then it won't continue searching the <div> until it finds a child with the class test — it just won't match anything. I'm not sure if that's what you want.