Cleaner, quieter test rig tests (#24073)

Add noise suppression. Refactor to modern facilities.

### Why was the ticket worth tackling?

It didn't have a ticket, but there was confusion on a ticket about the
noisy output. That is a waste of time, in a context where the build is
in flux.

I wanted to ensure that my recent fix to how lines are counted by the
test rig didn't break something. (There was just one semantic merge
conflict, for a check file.)

### How I fixed it

I finally noticed that the local test run correctly summarizes no
failures, even though the individual test echoed its failure state.

```
[info] Test run dotty.tools.vulpix.VulpixUnitTests finished: 0 failed, 0 ignored, 19 total, 23.642s
[info] Passed: Total 19, Failed 0, Errors 0, Passed 19
```
Then I noticed that the rig already has a flag for noise suppression, so
I added that incrementally.

Since the unit test file is not large, it was expedient to refactor it
to look more modern, but without other behavior changes.

### Why is this PR worth reviewing?

It improves readability of the test rig's unit test, but avoids futzing
with any operational semantics such as threading.

Removing the noisy output helps when scrolling through copious C.I.
output, where it looks like an error.

### What's the worse that could happen?

The build breaks in subtle ways.

Author: hamzaremmal

compiler/test/dotty/tools/vulpix/ParallelTesting.scala

@@ -1352,14 +1352,14 @@ trait ParallelTesting extends RunnerOrchestration:
      *  This behaviour is mainly needed for the tests that test the test suite.
      */
     def expectFailure: CompilationTest =
-      new CompilationTest(targets, times, shouldDelete, threadLimit, true, shouldSuppressOutput)
+      new CompilationTest(targets, times, shouldDelete, threadLimit, shouldFail = true, shouldSuppressOutput)
 
     /** Builds a `CompilationTest` where all output is suppressed
      *
      *  This behaviour is mainly needed for the tests that test the test suite.
      */
     def suppressAllOutput: CompilationTest =
-      new CompilationTest(targets, times, shouldDelete, threadLimit, shouldFail, true)
+      new CompilationTest(targets, times, shouldDelete, threadLimit, shouldFail, shouldSuppressOutput = true)
 
     /** Delete all output files generated by this `CompilationTest` */
     def delete(): Unit = targets.foreach(t => delete(t.outDir))

compiler/test/dotty/tools/vulpix/VulpixUnitTests.scala

@@ -1,107 +1,99 @@
 package dotty.tools
 package vulpix
 
-import scala.language.unsafeNulls
-
-import java.io.{File => JFile}
-import org.junit.Assert._
-import org.junit.{ Test, AfterClass }
-
-import scala.concurrent.duration._
-import scala.util.control.NonFatal
+import org.junit.{Test as test, AfterClass as tearDown}
 
 /** Unit tests for the Vulpix test suite */
-class VulpixUnitTests {
-  import VulpixUnitTests._
-  import TestConfiguration._
+class VulpixUnitTests:
+  import VulpixUnitTests.*
+  import TestConfiguration.*
 
-  implicit val _: SummaryReporting = new NoSummaryReport
+  given SummaryReporting = new NoSummaryReport
 
-  implicit def testGroup: TestGroup = TestGroup("VulpixTests")
+  given TestGroup = TestGroup("VulpixTests")
 
-  // To fail with something else than an AssertionError
-  def fail(): Unit = throw new Exception("didn't fail properly")
-
-  @Test def missingFile: Unit =
-    try {
+  @test def missingFile: Unit =
+    assertThrows[IllegalArgumentException](_ => true):
       compileFile("tests/vulpix-tests/unit/i-dont-exist.scala", defaultOptions).expectFailure.checkExpectedErrors()
-      fail()
-    } catch {
-      case _: IllegalArgumentException => // pass!
-    }
 
-  @Test def pos1Error: Unit =
+  @test def pos1Error: Unit =
     compileFile("tests/vulpix-tests/unit/posFail1Error.scala", defaultOptions).expectFailure.checkCompile()
 
-  @Test def negMissingAnnot: Unit =
-    compileFile("tests/vulpix-tests/unit/negMissingAnnot.scala", defaultOptions).expectFailure.checkExpectedErrors()
-
-  @Test def negAnnotWrongLine: Unit =
-    compileFile("tests/vulpix-tests/unit/negAnnotWrongLine.scala", defaultOptions).expectFailure.checkExpectedErrors()
-
-  @Test def negTooManyAnnots: Unit =
-    compileFile("tests/vulpix-tests/unit/negTooManyAnnots.scala", defaultOptions).expectFailure.checkExpectedErrors()
-
-  @Test def negNoPositionAnnot: Unit =
-    compileFile("tests/vulpix-tests/unit/negNoPositionAnnots.scala", defaultOptions).expectFailure.checkExpectedErrors()
-
-  @Test def negAnyPositionAnnot: Unit =
-    compileFile("tests/vulpix-tests/unit/negAnyPositionAnnots.scala", defaultOptions).checkExpectedErrors()
-
-  @Test def runCompileFail: Unit =
+  @test def negMissingAnnot: Unit =
+    compileFile("tests/vulpix-tests/unit/negMissingAnnot.scala", defaultOptions)
+      .suppressAllOutput
+      .expectFailure
+      .checkExpectedErrors()
+
+  @test def negAnnotWrongLine: Unit =
+    compileFile("tests/vulpix-tests/unit/negAnnotWrongLine.scala", defaultOptions)
+      .suppressAllOutput
+      .expectFailure
+      .checkExpectedErrors()
+
+  @test def negTooManyAnnots: Unit =
+    compileFile("tests/vulpix-tests/unit/negTooManyAnnots.scala", defaultOptions)
+      .suppressAllOutput
+      .expectFailure
+      .checkExpectedErrors()
+
+  @test def negNoPositionAnnot: Unit =
+    compileFile("tests/vulpix-tests/unit/negNoPositionAnnots.scala", defaultOptions)
+      .suppressAllOutput
+      .expectFailure
+      .checkExpectedErrors()
+
+  @test def negAnyPositionAnnot: Unit =
+    compileFile("tests/vulpix-tests/unit/negAnyPositionAnnots.scala", defaultOptions)
+      .suppressAllOutput
+      .checkExpectedErrors()
+
+  @test def runCompileFail: Unit =
     compileFile("tests/vulpix-tests/unit/posFail1Error.scala", defaultOptions).expectFailure.checkRuns()
 
-  @Test def runWrongOutput1: Unit =
+  @test def runWrongOutput1: Unit =
     compileFile("tests/vulpix-tests/unit/runWrongOutput1.scala", defaultOptions).expectFailure.checkRuns()
 
-  @Test def runWrongOutput2: Unit =
+  @test def runWrongOutput2: Unit =
     compileFile("tests/vulpix-tests/unit/runWrongOutput2.scala", defaultOptions).expectFailure.checkRuns()
 
-  @Test def runDiffOutput1: Unit =
+  @test def runDiffOutput1: Unit =
     compileFile("tests/vulpix-tests/unit/runDiffOutput1.scala", defaultOptions).expectFailure.checkRuns()
 
-  @Test def runStackOverflow: Unit =
+  @test def runStackOverflow: Unit =
     compileFile("tests/vulpix-tests/unit/stackOverflow.scala", defaultOptions).expectFailure.checkRuns()
 
-  @Test def runOutRedirects: Unit =
+  @test def runOutRedirects: Unit =
     compileFile("tests/vulpix-tests/unit/i2147.scala", defaultOptions).expectFailure.checkRuns()
 
-  @Test def infiteNonRec: Unit =
+  @test def infiniteNonRec: Unit =
     compileFile("tests/vulpix-tests/unit/infinite.scala", defaultOptions).expectFailure.checkRuns()
 
-  @Test def infiteTailRec: Unit =
+  @test def infiniteTailRec: Unit =
     compileFile("tests/vulpix-tests/unit/infiniteTail.scala", defaultOptions).expectFailure.checkRuns()
 
-  @Test def infiniteAlloc: Unit =
+  @test def infiniteAlloc: Unit =
     compileFile("tests/vulpix-tests/unit/infiniteAlloc.scala", defaultOptions).expectFailure.checkRuns()
 
-  @Test def deadlock: Unit =
+  @test def deadlock: Unit =
     compileFile("tests/vulpix-tests/unit/deadlock.scala", defaultOptions).expectFailure.checkRuns()
 
-  @Test def badJava: Unit =
-    try {
-      compileFile("tests/vulpix-tests/unit/BadJava.java", defaultOptions).suppressAllOutput.checkCompile()
-      fail()
-    } catch {
-      case ae: AssertionError => assertTrue(ae.getMessage.contains("java compilation failed"))
-    }
+  @test def badJava: Unit =
+    assertThrows[AssertionError](_.getMessage.contains("java compilation failed")):
+      compileFile("tests/vulpix-tests/unit/BadJava.java", defaultOptions)
+        .suppressAllOutput
+        .checkCompile()
 
-  @Test def runTimeout: Unit = {
+  @test def runTimeout: Unit =
     val fileName = s"tests/vulpix-tests/unit/timeout.scala"
-    try {
-      compileFile(fileName, defaultOptions).checkRuns()
-      fail()
-    } catch {
-      case ae: AssertionError =>
-        val expect = """(?m).*test '.+' timed out.*"""
-        val actual = ae.getMessage.linesIterator.toList.last
-        assert(actual.matches(expect), "actual = " + actual)
-    }
-  }
-}
-
-
-object VulpixUnitTests extends ParallelTesting {
+    val expect = """(?m).*test '.+' timed out.*"""
+    assertThrows[AssertionError](_.getMessage.linesIterator.toList.last.matches(expect)):
+      compileFile(fileName, defaultOptions)
+        .suppressAllOutput
+        .checkRuns()
+
+object VulpixUnitTests extends ParallelTesting:
+  import scala.concurrent.duration.*
   def maxDuration = 3.seconds
   def numberOfSlaves = 5
   def safeMode = sys.env.get("SAFEMODE").isDefined
@@ -110,6 +102,5 @@ object VulpixUnitTests extends ParallelTesting {
   def updateCheckFiles: Boolean = false
   def failedTests = None
 
-  @AfterClass
-  def tearDown() = this.cleanup()
-}
+  @tearDown
+  def tearDown() = cleanup()