SI-6502 Convert test to asserts

[som-snytt]

This saves a check file in the crowded test directory.

[som-snytt]

Not trying to be obnoxious with this PR.

Actually, I wanted to do something like the following, but it says "class not found":

object Test extends ReplTest {
  def code = {
    testOutput.jfile.mkdirs()
    s"""
      |:reset -Yrepl-outdir ${jarnr(1)}
      |:pa -raw
      |package test { object Test { def test() = println("testing...") } }
      |\u0004
      |:reset -Yrepl-outdir ${testOutput.path}
      |:require ${jarnr(1)}
      |test.Test.test()
      |
      |
    """.stripMargin
  }

  def jarnr(n: Int) = s"${testOutput.toAbsolute.path}/test${n}.jar"
  [etc]

That works in the REPL, so it should work under partest.

I had to tweak the paste code to handle the "raw" ctl-D, but otherwise, not sure why it didn't work the first time.

[retronym]

Cheers!