Chlorophyllum mushrooms are somewhat common in urban habitats and the genus includes both edible and poisonous species.
The must useful test for assessing the edibility of Chlorophyllum mushrooms is a spore print. White-spored Chlorophyllum brunneum, and Chlorophyllum olivieri are both edible, while the green-spored Chlorophyllum molybdites is poisonous.
Pay attention to young and older specimens, gill attachment, presence of a veil on the stem, discoloration when handling/cutting, and especially spore color.