Should we include more dependencies to TestModule.<Framework>Module

[lefou]

We currently don't add the dependencies to a concrete test runner in our TestModule traits.

That means, users need to remember to add the correct dependencies themselves.

The reasons are twofold.

1. We don't want to maintain version in these traits
2. In some cases it's not easy to determine the best set of dependencies (e.g. scalatest)

This lightweight approach is a bit inconvenient, since you need to look up the correct dependencies every time.

What about adding the dependencies, such that just adding a extends TestModule.Utest is enough to run a test? To keep version-update induced maintenance low, we could:

1. Introduce a dedicated version target. Either a specific (TestModule.Utest.utestVersion, TestModule.ZioTest.zioTestVersion) or some generic (TestModule.Utest.testFrameworkVersion).

2. Introduce additional targets, to select a specific set of features and deduce the respective needed dependencies from it. (TestModule.ScalaTest.suiteStyles: T[Seq[SuiteStyle]]. E.g. to select free we add scalatest-freespec dependency)

It would be also an opportunity to abstract over some framework specific settings like parallel running of suites/test or failure reporting.

[lihaoyi]

For the Java TestModules, we currently do include dependencies. e.g. for Junit4, Junit5, and TestNg:

mill/scalalib/src/mill/scalalib/TestModule.scala

Lines 243 to 272 in 7147d76

	trait TestNg extends TestModule {
	override def testFramework: T[String] = "mill.testng.TestNGFramework"
	override def ivyDeps: T[Agg[Dep]] = T {
	super.ivyDeps() ++ Agg(
	ivy"com.lihaoyi:mill-contrib-testng:${mill.api.BuildInfo.millVersion}"
	)
	}
	}
	/**
	* TestModule that uses JUnit 4 Framework to run tests.
	* You may want to provide the junit dependency explicitly to use another version.
	*/
	trait Junit4 extends TestModule {
	override def testFramework: T[String] = "com.novocode.junit.JUnitFramework"
	override def ivyDeps: T[Agg[Dep]] = T {
	super.ivyDeps() ++ Agg(ivy"com.novocode:junit-interface:0.11")
	}
	}
	/**
	* TestModule that uses JUnit 5 Framework to run tests.
	* You may want to provide the junit dependency explicitly to use another version.
	*/
	trait Junit5 extends TestModule {
	override def testFramework: T[String] = "net.aichler.jupiter.api.JupiterFramework"
	override def ivyDeps: T[Agg[Dep]] = T {
	super.ivyDeps() ++ Agg(ivy"net.aichler:jupiter-interface:0.9.0")
	}
	}

[lefou]

Yeah, these include the sbt.testing.framework (which is uncommon in the Java world), and (transitively) the test runner.