Fuse Testing Methods

Non-destructive testing used by consumers

Look at them. If the center wire has not melted, it's probably not 'blown.'

Check with an ohmmeter. If it measures low resistance, it's not blown. If it has really high resistance, it is open.

Destructive Testing used for Quality Control
Run current through a fuse, and record the current when it melted.

You can't easily measure to predict when a fuse will melt, but you can predict its melting current by trial and error, then employing close tolerances on metallurgy and thickness of the element.

Any open circuit, whether from a melted fuse element, a broken connector, or corrosion between two metals, will prevent current flow.

Best Regards,
Jim