You can test your butane by putting it in the freezer as butane boils at about 33 degrees F. So freeze the container then go out side or in a well ventilated area take and discharge the liquid into a bowl or dish that has also been chilled in the freezer. The butane and dish will warm up as it does the butane will boil off (no sparks) Most of the time some water will condense on the cold surface allow the water to evaporate. Now check for any residue if no residue remains your butane is pure enough for a super clean extraction. It may have had a small amount of other gases present but this is not a concern as they will evaporate out of your goodies along with the butane.
Most noteable brands wont leave anything i'd say anything triple to quadruple refined is a waste to test it for purity. Dunno bought that but yea vector claims to be cleaner. Hardly any difference though, I buy whatever is cheaper.
Any solvent can be tested in this manner to be sure it evaporates clean. Butane is a gas above its boiling point that is why the freeze is necessary. Its also best to freeze your butane before extractions other wise it boils off until it gets below its boiling point before it remains as a liquid. As it boils it transfers the thermal energy (heat) away into its gaseous state. This also makes tubes unnecessary if you work with liquid butane all you need are two jars and a coffee filter and a Pyrex baking dish. One jar contains your trim or powdered bud that has been chilled in the freezer. Then discharge the liquid butane into this jar and swirl it for 30 seconds or so. Its best to wear gloves or you will freeze your skin. Allow it to settle then pour it into your filter into a second chilled jar. Once it is filtered pour it into a Pyrex baking dish for final evaporation. Allow any condensed water to evaporate and scrape up the honey oil with a razor blade. This method is superior to alcohol extractions because you are working below the freezing point of water 32 degrees F. The advantage being that all water remains frozen and does not carry over into your final product. If liquid water is present in your solvent it will dissolve things other than oil that you do not want. It is difficult to get 100% pure alcohol most contain some amount of water that will dissolve things other than oil that contaminate the final extraction. You can use distillation to remove the water from alcohol but it can be complicated and dangerous if you do not know what you are doing. Any solvent can be made pure by distillation. Yes testing is likely unnecessary with butane any brand I have ever used evaporates clean.