Testing Proxies?

I have just bought my first private proxies for buyproxy.org, but my question is how do you test them after using them.

I have been suing them for a day, but now it feels like some proxies no longer works...so how would I test that.

Can you do this in ScrapeBox? But what if you don't have ScrapeBox, how would you know which proxies are still working and which aren't any longer?

Best to put them in a browser to manually check them. Several tutorials that show how to do that with each browser.