Add .csv file extension to the download.

[jozzhart]

[mwinteringham]

+1

[trevorwilliams]

+1

[dgmike]

:+1: but need to correct the tests....

[dgmike]

Looking for other issues, I founded https://github.com/nulltask/express-csv/issues/8#issuecomment-28124841 that resolves this issue without change the extension.

response.setHeader('Content-disposition', 'attachment; filename=testing.csv')

[sabrams]

+1

[edu2004eu]

This should not come as a separate feature, because you can already achieve this with a header, like @dgmike said in his previous comment.