How do I specify specific test from the build.sbt - scala

Question

How do I can specify the test from the build.sbt file , I wanted to run one test only and I used the filter as in the sbt docs, but it doesn't work with me, this is my code I have two test classes and in my sbt I specify test1 to be rub but it seems that the two test are running at the same time any one know what I should do ?
Test1Demo.scala
import org.scalatest.{FlatSpec, Matchers}
class Test1Demo extends FlatSpec with Matchers{
"value of x " should " be 9 " in { assert(my.App.x == 9) }
}
Test2Demo.scala
import org.scalatest.{FlatSpec, Matchers}
class Test2Demo extends FlatSpec with Matchers{
"value of y " should " be 8 " in { assert(my.App2.y == 8) }
}
build.sbt
version := "0.1"
scalaVersion := "2.12.8"
libraryDependencies += "org.scalatest" %% "scalatest" % "3.0.5" % Test
testOptions in Test := Seq(Tests.Filter(s => s.startsWith("Test1")))
the output :
[info] Done updating.
[info] Compiling 2 Scala sources to /home/****/target/scala-2.12/classes ...
[info] Done compiling.
[info] Compiling 2 Scala sources to /home/****/target/scala-2.12/test-classes ...
[info] Done compiling.
[info] Test2Demo:
[info] value of y
[info] - should be 8
[info] Test1Demo:
[info] value of x
[info] - should be 9
[info] Run completed in 6 seconds, 365 milliseconds.
[info] Total number of tests run: 2
[info] Suites: completed 2, aborted 0
[info] Tests: succeeded 2, failed 0, canceled 0, ignored 0, pending 0
[info] All tests passed.
[success] Total time: 264 s, completed Apr 15, 2019 2:47:10 PM

Answer 1

If you want to run value of x test from Test1Demo:
testOnly *Test1Demo -- -z value
This sbt command will run only the tests whose name includes the substring "value".
For exact match rather than substring, use -t instead of -z.
Pay attention to -- (two -, not one)