The Front Porch Test is a test in which Lily tries to picture how a relationship would be in the future. The people who pass The Front Porch Test are people who Lily believes would fit in with them when they grow old. The scene in which this is explained shows Marshall, Lily, and Ted playing bridge. Lily hopes that whoever passes this test will fill the extra spot on the porch. I think this is so cute because they just want to know that their friend’s future spouse will fits in with them. I hope my friends are this considerate!