Sbt run tests from src/main/scala instead of src/test/scala? - scala

Question

Say I have a scalatest class in main/scala, like
import org.scalatest.FunSuite
class q3 extends FunSuite {
test("6 5 4 3 2 1") {
val digits = Array(6,5,4,3,2,1)
assert(digits.sorted === Array(1,2,3,4,5,6))
}
}
How do I run it with sbt?
I've tried sbt test, sbt testOnly, sbt "testOnly *q3" and they all had output like
[info] Run completed in 44 milliseconds.
[info] Total number of tests run: 0
[info] Suites: completed 0, aborted 0
[info] Tests: succeeded 0, failed 0, canceled 0, ignored 0, pending 0
[info] No tests were executed.
[info] No tests to run for Test / testOnly
A similar question from a few years back said they successfully used testOnly but I can't get it to work.
The metals extension on VSCode shows a "test" link when the file is open which successfully runs the test, but doesn't show how it does that. I want to know how to do it through sbt.

Answer 1

Put ScalaTest on Compile classpath in build.sbt like so
libraryDependencies += "org.scalatest" %% "scalatest" % "3.1.0"
and then call org.scalatest.run runner explicitly from within an App, for example,
object MainTests extends App {
org.scalatest.run(new ExampleSpec)
}
Putting it together we have in src/main/scala/example/MainTests.scala
package example
import org.scalatest.matchers.should.Matchers
import org.scalatest.flatspec.AnyFlatSpec
import collection.mutable.Stack
import org.scalatest._
class ExampleSpec extends AnyFlatSpec with Matchers {
"A Stack" should "pop values in last-in-first-out order" in {
val stack = new Stack[Int]
stack.push(1)
stack.push(2)
stack.pop() should be (2)
stack.pop() should be (1)
}
}
object MainTests extends App {
org.scalatest.run(new ExampleSpec)
}
and run it with runMain example.MainTests. Furthermore, we could gather tests in Suites and execute all like so
class ExampleASpec extends FlatSpec with Matchers {
"ExampleA" should "run" in { succeed }
}
class ExampleBSpec extends FlatSpec with Matchers {
"ExampleB" should "run" in { succeed }
}
class ExampleSuite extends Suites(
new ExampleASpec,
new ExampleBSpec,
)
object MainTests extends App {
(new ExampleSuite).execute()
}