perf(core): slim down per-mutant debug log message

Logging the whole MutantWithId case class stringified the entire
mutated tree; log only the useful fields instead

Author: hugo-vrijswijk

modules/core/src/main/scala/stryker4s/run/MutantRunner.scala

@@ -201,7 +201,12 @@ class MutantRunner(
       .emits(testableMutants)
       .through(testRunnerPool.run { case (testRunner, (path, mutant)) =>
         val coverageForMutant = coverageExclusions.coveredMutants.getOrElse(mutant.id, Seq.empty)
-        IO(log.debug(s"Running mutant $mutant")) *>
+        IO(
+          log.debug {
+            val metadata = mutant.mutatedCode.metadata
+            s"Running mutant ${mutant.id.value} (${metadata.mutatorName} at ${metadata.location.show})"
+          }
+        ) *>
           testRunner.runMutant(mutant, coverageForMutant).timed.flatMap { case (duration, result) =>
             IO(log.debug(s"Mutant ${mutant.id} tested in ${duration.toHumanReadable}")).as(path -> result)
           }

modules/core/src/test/scala/stryker4s/run/MutantRunnerTest.scala

@@ -194,8 +194,11 @@ class MutantRunnerTest extends Stryker4sIOSuite with LogMatchers with TestData {
     val mutants = NonEmptyVector.one(mutant)
     val mutatedFile = MutatedFile(file, "def foo = 4".parseDef, mutants)
 
+    val metadata = mutant.mutatedCode.metadata
     sut(Vector(mutatedFile))
-      .assertLoggedDebug(s"Running mutant $mutant")
+      .assertLoggedDebug(
+        s"Running mutant ${mutant.id.value} (${metadata.mutatorName} at ${metadata.location.show})"
+      )
       .assertLoggedDebug("Mutant 1 tested in")
   }