Define Custom Tasks 

Define a Task that runs tests in specific sub-projects 

Consider a hypothetical multi-build project with 3 subprojects. The following defines a task myTestTask that will run the test Task in specific subprojects core and tools but not client:

lazy val core ="./core"))
lazy val tools ="./tools"))
lazy val client ="./client"))

lazy val myTestTask = taskKey[Unit]("my test task")

myTestTask := {
  (test in (core, Test)).value
  (test in (tools, Test)).value


sbt Reference Manual
    1. Define Custom Tasks