Do you observe the halide test in the upper layer or lower layer

lower layer

Explanation:

Usually to identify halide ions in solution you use silver nitrate which readly react with Cl⁻, Br⁻ and I⁻ ions to form silver halide salts with different colors depending on the ion present in the solution .

Now, because the silver halide salts are insoluble in water and have a density higher that the water they will stay in the lower part of the test tube.