Add a run file with a consistent test task

run

@@ -0,0 +1,23 @@
+#!/usr/bin/env bash
+
+set -o errexit
+set -o nounset
+
+PATH=${PATH}:./vendor/bin
+
+# Display a list of all available commands.
+function help {
+  printf "%s <task> [args]\n\nTasks:\n" "${0}"
+
+  compgen -A function | grep -v "^_" | cat -n
+
+  printf "\nExtended help:\n  Each task has comments for general usage\n"
+}
+
+# Run PHPUnit tests.
+function test {
+  paratest --group lessons "${@}"
+}
+
+TIMEFORMAT=$'\nTask completed in %3lR'
+time "${@:-help}"