Which test is used to detect nitrogen, sulfur, and halogens?

Lassaignes test should be the answer

The test used to detect nitrogen, sulfur, and halogens is Lassaigne's test

Explanation:

The Lassaigne's test also known as sodium fusion test is used in elemental analysis for the qualitative measurements of the presence of elements such as halogens, nitrogen, and sulphur, in any organic compound. It was developed by J. L. Lassaigne. This is done by fusing the organic compound with sodium metal. The ionic compounds formed during the fusion are taken up in aqueous solution and can be detected by simple chemical tests taken in laboratory.