diff --git a/shell.nix b/shell.nix
index fede276..6f3be7a 100644
--- a/shell.nix
+++ b/shell.nix
@@ -103,6 +103,13 @@ pkgs.mkShell {
       $COMPOSE exec php php bin/phpunit "$@"
     }
 
+    dev-coverage() {
+      # Code coverage as a plain text table in the terminal (needs Xdebug, which is installed).
+      # --colors=never keeps the table readable (the ANSI colors garble it).
+      # Pass-through args, e.g. scope to one class: dev-coverage --filter BucketRoomCalculator
+      $COMPOSE exec -e XDEBUG_MODE=coverage php php bin/phpunit --coverage-text --colors=never "$@"
+    }
+
     dev-stan() {
       # Warm the dev cache so phpstan-symfony can read the compiled container, then analyse.
       $COMPOSE exec php php bin/console cache:warmup --quiet