There is a small test BUT you may not want to use it on router bits.
It's a grinder test, when you grind steel the sparks will tell you what the steel is but most router bits that have carbide blades you can tell just by looking at them.
And the most common router bits are HSS that's to say if they are round over and alike.
Most home owners don't have the high end soild carb. bits,one bit can cost almost the same as a full HSS set.
You can also check the weight. Carbide is heavy. Also the corner of a file will skip across carbide like it was glass. And the color of carbide is duller than the shine of HSS.
About the only solid carbide cutters will be straight spiral cutters, the rest will have a piece of carbide silver soldered to a steel body of the cutter. The solder joint between the carbide and the tool body is easy to distinguish.
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