Slick TestKit


This chapter is based on the Slick TestKit Example template. The prefered way of reading this introduction is in Activator, where you can edit and run the code directly while reading the tutorial.

When you write your own database driver for Slick, you need a way to run all the standard unit tests on it (in addition to any custom tests you may want to add) to ensure that it works correctly and does not claim to support any capabilities which are not actually implemented. For this purpose the Slick unit tests have been factored out into a separate Slick TestKit project.

To get started, you can clone the Slick TestKit Example template which contains a copy of Slick’s standard PostgreSQL driver and all the infrastructure required to build and test it.


Its build.sbt file is straight-forward. Apart from the usual name and version settings, it adds the dependencies for Slick, the TestKit, junit-interface, Logback and the PostgreSQL JDBC driver, and it sets some options for the test runs:

libraryDependencies ++= Seq(
  "com.typesafe.slick" %% "slick" % "3.1.1",
  "com.typesafe.slick" %% "slick-testkit" % "3.1.1" % "test",
  "com.novocode" % "junit-interface" % "0.10" % "test",
  "ch.qos.logback" % "logback-classic" % "0.9.28" % "test",
  "postgresql" % "postgresql" % "9.1-901.jdbc4" % "test"

testOptions += Tests.Argument(TestFrameworks.JUnit, "-q", "-v", "-s", "-a")

parallelExecution in Test := false

logBuffered := false

There is a copy of Slick’s logback configuration in src/test/resources/logback-test.xml but you can swap out the logging framework if you prefer a different one.


The actual driver implementation can be found under src/main/scala.

Test Harness

In order to run the TestKit tests, you need to add a class that extends DriverTest, plus an implementation of TestDB which tells the TestKit how to connect to a test database, get a list of tables, clean up between tests, etc.

In the case of the PostgreSQL test harness (in src/test/slick/driver/test/MyPostgresTest.scala) most of the default implementations can be used out of the box. Only localTables and getLocalSequences require custom implementations. We also modify the driver’s capabilities to indicate that our driver does not support the JDBC getFunctions call:

class MyPostgresTest extends DriverTest(MyPostgresTest.tdb)

object MyPostgresTest {
  def tdb = new ExternalJdbcTestDB("mypostgres") {
    val driver = MyPostgresDriver
    override def localTables(implicit ec: ExecutionContext): DBIO[Vector[String]] =
      ResultSetAction[(String,String,String, String)](_.conn.getMetaData().getTables("", "public", null, null)).map { ts =>
        ts.filter(_._4.toUpperCase == "TABLE").map(_._3).sorted
    override def getLocalSequences(implicit session: profile.Backend#Session) = {
      val tables = ResultSetInvoker[(String,String,String, String)](_.conn.getMetaData().getTables("", "public", null, null))
      tables.buildColl[List].filter(_._4.toUpperCase == "SEQUENCE").map(_._3).sorted
    override def capabilities = super.capabilities - TestDB.capabilities.jdbcMetaGetFunctions

The name of a configuration prefix, in this case mypostgres, is passed to ExternalJdbcTestDB:

def tdb =
  new ExternalJdbcTestDB("mypostgres") ...

Database Configuration

Since the PostgreSQL test harness is based on ExternalJdbcTestDB, it needs to be configured in test-dbs/testkit.conf:

mypostgres.enabled = true
mypostgres.user = myuser
mypostgres.password = secret

There are several other configuration options that need to be set for an ExternalJdbcTestDB. These are defined with suitable defaults in testkit-reference.conf so that testkit.conf can be kept very simple in most cases.


Running sbt test discovers MyPostgresTest and runs it with TestKit’s JUnit runner. This in turn causes the database to be set up through the test harness and all tests which are applicable for the driver (as determined by the capabilities setting in the test harness) to be run.