[M2Ys4U]

Every test I've done (provided for free on the NHS, btw) has just been two red lines.

The control line doesn't show up until the buffer solution has wicked along the test strip, so the verification is "does the line next to the letter C show up?"

[labcomputer]

Yes, but the parent was writing about the Abbott Labs BinaxNOW test, specifically (which I have also used).

The directions indicate to verify that the blue control line is present prior to adding the swab, and that the test should not be used if the blue line is not present.

You can verify this for yourself by downloading the official instructions here: https://www.fda.gov/media/141570/download