From its source the Test flows west to Whitchurch then southwest to Stockbridge and then south past Romsey to its estuary. The upper river has a number of spring fed tributaries - The Bourne, The Dever, the River Anton, Wallop Brook and the Sombourne Stream join the river above Mottisfont.
Downstream of Mottisfont the river flows through the Hampshire basin where it is joined by the River Dun at Kimbridge and the Blackwater at Testwood. Below the junction of the Blackwater the river has many channels as it flows through the Lower Test Nature Reserve at Redbridge.
Although migratory fish have in the past been caught as far upstream as Longparish, the main salmon and sea trout fisheries are now downstream of Romsey, with the Nursling and Testwood fisheries considered the best. Most fish are caught by rods spinning lures or fishing the shrimp or prawn. Fishing with worms is prohibited. Some years ago the river keepers were keen to fish the fly for salmon and they developed the method of fishing a gold headed nymph fly known locally as the Hampshire Hog. On spotting a fish the fly was cast upstream and fished down to the fish in the same manner as in Czech nymph fishing.