SBT doesn't compile tests located in custom test source folders - scala

Question

I have 3 test source folders in my project. I have added the following key to build.sbt (version of SBT: 1.2.1):
sourceDirectories in Test := baseDirectory { base =>
Seq(
base / "src/test/common/scala",
base / "src/test/unit/scala",
base / "src/test/functional/scala"
)
}.value
SBT correctly recognized the folders:
sbt test:sourceDirectories
...
[info] Set current project to service (in build file:/myprojectfolder/)
[info] * /myprojectfolder/src/test/common/scala
[info] * /myprojectfolder/src/test/unit/scala
[info] * /myprojectfolder/src/test/functional/scala
but test:compile doesn't produce any test classes in target/scala-2.11/test-classes and in result test task doesn't run any tests.
I'm using ScalaTest 3.0.5 although that doesn't seem relevant.
Any ideas why SBT ignores test scala sources during compilation?

Answer 1

Thank you manuzhang for useful comments. Indeed the following change did the trick:
instead of
sourceDirectories in Test := baseDirectory { base =>
Seq(
base / "src/test/common/scala",
base / "src/test/unit/scala",
base / "src/test/functional/scala"
)
}.value
I used
unmanagedSourceDirectories in Test := baseDirectory { base =>
Seq(
base / "src/test/common/scala",
base / "src/test/unit/scala",
base / "src/test/functional/scala"
)
}.value