diff --git a/compile b/compile
index 5505e42..444f591 100755
--- a/compile
+++ b/compile
@@ -4,6 +4,6 @@
 # but do *not* change its name.
 
 # feel free to adjust to suit the specific internal flags of your compiler
-./wacc-compiler "$@"
+./wacc-compiler --output . "$@"
 
 exit $?
diff --git a/project.scala b/project.scala
index 4deaa08..8edf035 100644
--- a/project.scala
+++ b/project.scala
@@ -5,23 +5,18 @@
 //> using dep com.github.j-mie6::parsley::5.0.0-M10
 //> using dep com.github.j-mie6::parsley-cats::1.5.0
 //> using dep com.lihaoyi::os-lib::0.11.4
-//> using dep com.github.scopt::scopt::4.1.0
+//> using dep org.typelevel::cats-core::2.13.0
+//> using dep org.typelevel::cats-effect::3.5.7
+//> using dep com.monovore::decline::2.5.0
+//> using dep com.monovore::decline-effect::2.5.0
+//> using dep org.typelevel::log4cats-slf4j::2.7.0
+//> using dep org.slf4j:slf4j-simple:2.0.17
 //> using test.dep org.scalatest::scalatest::3.2.19
+//> using dep org.typelevel::cats-effect-testing-scalatest::1.6.0
 
-// these are all sensible defaults to catch annoying issues
+// sensible defaults for warnings and compiler checks
 //> using options -deprecation -unchecked -feature
 //> using options -Wimplausible-patterns -Wunused:all
 //> using options -Yexplicit-nulls -Wsafe-init -Xkind-projector:underscores
 
-// these will help ensure you have access to the latest parsley releases
-// even before they land on maven proper, or snapshot versions, if necessary.
-// just in case they cause problems, however, keep them turned off unless you
-// specifically need them.
-// using repositories sonatype-s01:releases
-// using repositories sonatype-s01:snapshots
-
-// these are flags used by Scala native: if you aren't using scala-native, then they do nothing
-// lto-thin has decent linking times, and release-fast does not too much optimisation.
-// using nativeLto thin
-// using nativeGc commix
-// using nativeMode release-fast
+// repositories for pre-release versions if needed
diff --git a/src/main/wacc/Main.scala b/src/main/wacc/Main.scala
index fc9fb45..d964657 100644
--- a/src/main/wacc/Main.scala
+++ b/src/main/wacc/Main.scala
@@ -1,92 +1,159 @@
 package wacc
 
 import scala.collection.mutable
-import cats.data.Chain
+import cats.data.{Chain, NonEmptyList}
 import parsley.{Failure, Success}
-import scopt.OParser
-import java.io.File
-import java.io.PrintStream
+
+import java.nio.file.{Files, Path}
+import cats.syntax.all._
+
+import cats.effect.IO
+import cats.effect.ExitCode
+
+import com.monovore.decline._
+import com.monovore.decline.effect._
+
+import org.typelevel.log4cats.slf4j.Slf4jLogger
+import org.typelevel.log4cats.Logger
 
 import assemblyIR as asm
+import cats.data.ValidatedNel
 
-case class CliConfig(
-    file: File = new File(".")
-)
+/*
+TODO:
+  1) IO correctness
+  2) Errors can be handled more gracefully - currently, parallelised compilation is not fail fast as far as I am aware
+  3) splitting the file up and nicer refactoring
+  4) logging could be removed
+  5) general cleanup and comments (things like replacing home/<user> with ~ , and names of parameters and args, descriptions etc)
+ */
 
-val cliBuilder = OParser.builder[CliConfig]
-val cliParser = {
-  import cliBuilder._
-  OParser.sequence(
-    programName("wacc-compiler"),
-    help('h', "help")
-      .text("Prints this help message"),
-    arg[File]("<file>")
-      .text("Input WACC source file")
-      .required()
-      .action((f, c) => c.copy(file = f))
-      .validate(f =>
-        if (!f.exists) failure("File does not exist")
-        else if (!f.isFile) failure("File must be a regular file")
-        else if (!f.getName.endsWith(".wacc"))
-          failure("File must have .wacc extension")
-        else success
-      )
-  )
+private val SUCCESS = ExitCode.Success.code
+private val ERROR = ExitCode.Error.code
+
+given logger: Logger[IO] = Slf4jLogger.getLogger[IO]
+
+val logOpt: Opts[Boolean] =
+  Opts.flag("log", "Enable logging for additional compilation details", short = "l").orFalse
+
+def validateFile(path: Path): ValidatedNel[String, Path] = {
+  (for {
+    // TODO: redundant 2nd parameter :(
+    _ <- Either.cond(Files.exists(path), (), s"File '${path}' does not exist")
+    _ <- Either.cond(Files.isRegularFile(path), (), s"File '${path}' must be a regular file")
+    _ <- Either.cond(path.toString.endsWith(".wacc"), (), "File must have .wacc extension")
+  } yield path).toValidatedNel
 }
 
+val filesOpt: Opts[NonEmptyList[Path]] =
+  Opts.arguments[Path]("files").mapValidated {
+    _.traverse(validateFile)
+  }
+
+val outputOpt: Opts[Option[Path]] =
+  Opts
+    .option[Path]("output", metavar = "path", help = "Output directory for compiled files.")
+    .validate("Must have permissions to create & access the output path") { path =>
+      try {
+        Files.createDirectories(path)
+        true
+      } catch {
+        case e: java.nio.file.AccessDeniedException =>
+          false
+      }
+    }
+    .validate("Output path must be a directory") { path =>
+      Files.isDirectory(path)
+    }
+    .orNone
+
 def frontend(
     contents: String
-)(using stdout: PrintStream): Either[microWacc.Program, Int] = {
+): Either[NonEmptyList[Error], microWacc.Program] =
   parser.parse(contents) match {
+    case Failure(msg) => Left(NonEmptyList.one(Error.SyntaxError(msg)))
     case Success(prog) =>
       given errors: mutable.Builder[Error, List[Error]] = List.newBuilder
+
       val (names, funcs) = renamer.rename(prog)
       given ctx: typeChecker.TypeCheckerCtx = typeChecker.TypeCheckerCtx(names, funcs, errors)
       val typedProg = typeChecker.check(prog)
-      if (errors.result.nonEmpty) {
-        given errorContent: String = contents
-        Right(
-          errors.result
-            .map { error =>
-              printError(error)
-              error match {
-                case _: Error.InternalError => 201
-                case _                      => 200
-              }
-            }
-            .max()
-        )
-      } else Left(typedProg)
-    case Failure(msg) =>
-      stdout.println(msg)
-      Right(100)
-  }
-}
 
-val s = "enter an integer to echo"
+      NonEmptyList.fromList(errors.result) match {
+        case Some(errors) => Left(errors)
+        case None         => Right(typedProg)
+      }
+  }
+
 def backend(typedProg: microWacc.Program): Chain[asm.AsmLine] =
   asmGenerator.generateAsm(typedProg)
 
-def compile(filename: String, outFile: Option[File] = None)(using
-    stdout: PrintStream = Console.out
-): Int =
-  frontend(os.read(os.Path(filename))) match {
-    case Left(typedProg) =>
-      val asmFile = outFile.getOrElse(File(filename.stripSuffix(".wacc") + ".s"))
-      val asm = backend(typedProg)
-      writer.writeTo(asm, PrintStream(asmFile))
-      0
-    case Right(exitCode) => exitCode
-  }
+def compile(
+    filePath: Path,
+    outputDir: Option[Path],
+    log: Boolean
+): IO[Int] = {
+  val logAction: String => IO[Unit] =
+    if (log) logger.info(_)
+    else (_ => IO.unit)
 
-def main(args: Array[String]): Unit =
-  OParser.parse(cliParser, args, CliConfig()) match {
-    case Some(config) =>
-      System.exit(
-        compile(
-          config.file.getAbsolutePath,
-          outFile = Some(File(".", config.file.getName.stripSuffix(".wacc") + ".s"))
-        )
-      )
-    case None =>
-  }
+  def readSourceFile: IO[String] =
+    IO.blocking(os.read(os.Path(filePath)))
+
+  // TODO: path, file , the names are confusing (when Path is the type but we are working with files)
+  def writeOutputFile(typedProg: microWacc.Program, outputPath: Path): IO[Unit] =
+    writer.writeTo(backend(typedProg), outputPath) *>
+      logger.info(s"Success: ${outputPath.toAbsolutePath}")
+
+  def processProgram(contents: String, outDir: Path): IO[Int] =
+    frontend(contents) match {
+      case Left(errors) =>
+        val code = errors.map(err => err.exitCode).toList.min
+        given errorContent: String = contents
+        val errorMsg = errors.map(formatError).toIterable.mkString("\n")
+        for {
+          _ <- logAction(s"Compilation failed for $filePath\nExit code: $code")
+          _ <- IO.blocking(
+            // Explicit println since we want this to always show without logger thread info e.t.c.
+            println(s"Compilation failed for ${filePath.toAbsolutePath}:\n$errorMsg")
+          )
+        } yield code
+
+      case Right(typedProg) =>
+        val outputFile = outDir.resolve(filePath.getFileName.toString.stripSuffix(".wacc") + ".s")
+        writeOutputFile(typedProg, outputFile).as(SUCCESS)
+    }
+
+  for {
+    contents <- readSourceFile
+    _ <- logAction(s"Compiling file: ${filePath.toAbsolutePath}")
+    exitCode <- processProgram(contents, outputDir.getOrElse(filePath.getParent))
+  } yield exitCode
+}
+
+def compileCommandParallel(
+    files: NonEmptyList[Path],
+    log: Boolean,
+    outDir: Option[Path]
+): IO[ExitCode] =
+  files
+    .parTraverse { file => compile(file.toAbsolutePath, outDir, log) }
+    .map { exitCodes =>
+      exitCodes.filter(_ != 0) match {
+        case Nil        => ExitCode.Success
+        case errorCodes => ExitCode(errorCodes.min)
+      }
+    }
+
+object Main
+    extends CommandIOApp(
+      name = "wacc",
+      header = "The ultimate WACC compiler",
+      version = "1.0"
+    ) {
+  def main: Opts[IO[ExitCode]] =
+    (filesOpt, logOpt, outputOpt).mapN { (files, log, outDir) =>
+      compileCommandParallel(files, log, outDir)
+    }
+
+}
diff --git a/src/main/wacc/backend/writer.scala b/src/main/wacc/backend/writer.scala
index 3c8dcfd..a339f55 100644
--- a/src/main/wacc/backend/writer.scala
+++ b/src/main/wacc/backend/writer.scala
@@ -1,12 +1,42 @@
 package wacc
 
-import java.io.PrintStream
+import cats.effect.Resource
+import java.nio.charset.StandardCharsets
+import java.io.BufferedWriter
+import java.io.FileWriter
 import cats.data.Chain
+import cats.effect.IO
+
+import org.typelevel.log4cats.Logger
+import java.nio.file.Path
 
 object writer {
   import assemblyIR._
 
-  def writeTo(asmList: Chain[AsmLine], printStream: PrintStream): Unit = {
-    asmList.iterator.foreach(printStream.println)
-  }
+  // TODO: Judging from documentation it seems as though IO.blocking is the correct choice
+  // But needs checking
+
+  /** Creates a resource safe BufferedWriter */
+  private def bufferedWriter(outputPath: Path): Resource[IO, BufferedWriter] =
+    Resource.make {
+      IO.blocking(new BufferedWriter(new FileWriter(outputPath.toFile, StandardCharsets.UTF_8)))
+    } { writer =>
+      IO.blocking(writer.close())
+        .handleErrorWith(_ => IO.unit) // TODO: ensures writer is closed even if an error occurs
+    }
+
+  /** Write line safely into a BufferedWriter */
+  private def writeLines(writer: BufferedWriter, lines: Chain[AsmLine]): IO[Unit] =
+    IO.blocking {
+      lines.iterator.foreach { line =>
+        writer.write(line.toString)
+        writer.newLine()
+      }
+    }
+
+  /** Main function to write assembly to a file */
+  def writeTo(asmList: Chain[AsmLine], outputPath: Path)(using logger: Logger[IO]): IO[Unit] =
+    bufferedWriter(outputPath).use {
+      writeLines(_, asmList)
+    }
 }
diff --git a/src/main/wacc/frontend/Error.scala b/src/main/wacc/frontend/Error.scala
index 9c02a60..e515494 100644
--- a/src/main/wacc/frontend/Error.scala
+++ b/src/main/wacc/frontend/Error.scala
@@ -2,7 +2,9 @@ package wacc
 
 import wacc.ast.Position
 import wacc.types._
-import java.io.PrintStream
+
+private val SYNTAX_ERROR = 100
+private val SEMANTIC_ERROR = 200
 
 /** Error types for semantic errors
   */
@@ -15,6 +17,15 @@ enum Error {
   case SemanticError(pos: Position, msg: String)
   case TypeMismatch(pos: Position, expected: SemType, got: SemType, msg: String)
   case InternalError(pos: Position, msg: String)
+
+  case SyntaxError(msg: String)
+}
+
+extension (e: Error) {
+  def exitCode: Int = e match {
+    case Error.SyntaxError(_) => SYNTAX_ERROR
+    case _                    => SEMANTIC_ERROR
+  }
 }
 
 /** Function to handle printing the details of a given semantic error
@@ -24,71 +35,81 @@ enum Error {
   * @param errorContent
   *   Contents of the file to generate code snippets
   */
-def printError(error: Error)(using errorContent: String, stdout: PrintStream): Unit = {
-  stdout.println("Semantic error:")
-  error match {
-    case Error.DuplicateDeclaration(ident) =>
-      printPosition(ident.pos)
-      stdout.println(s"Duplicate declaration of identifier ${ident.v}")
-      highlight(ident.pos, ident.v.length)
-    case Error.UndeclaredVariable(ident) =>
-      printPosition(ident.pos)
-      stdout.println(s"Undeclared variable ${ident.v}")
-      highlight(ident.pos, ident.v.length)
-    case Error.UndefinedFunction(ident) =>
-      printPosition(ident.pos)
-      stdout.println(s"Undefined function ${ident.v}")
-      highlight(ident.pos, ident.v.length)
-    case Error.FunctionParamsMismatch(id, expected, got, funcType) =>
-      printPosition(id.pos)
-      stdout.println(s"Function expects $expected parameters, got $got")
-      stdout.println(
-        s"(function ${id.v} has type (${funcType.params.mkString(", ")}) -> ${funcType.returnType})"
-      )
-      highlight(id.pos, 1)
-    case Error.TypeMismatch(pos, expected, got, msg) =>
-      printPosition(pos)
-      stdout.println(s"Type mismatch: $msg\nExpected: $expected\nGot: $got")
-      highlight(pos, 1)
-    case Error.SemanticError(pos, msg) =>
-      printPosition(pos)
-      stdout.println(msg)
-      highlight(pos, 1)
-    case wacc.Error.InternalError(pos, msg) =>
-      printPosition(pos)
-      stdout.println(s"Internal error: $msg")
-      highlight(pos, 1)
+def formatError(error: Error)(using errorContent: String): String = {
+  val sb = new StringBuilder()
+
+  /** Function to format the position of an error
+    *
+    * @param pos
+    *   Position of the error
+    */
+  def formatPosition(pos: Position): Unit = {
+    sb.append(s"(line ${pos.line}, column ${pos.column}):\n")
   }
 
-}
-
-/** Function to highlight a section of code for an error message
-  *
-  * @param pos
-  *   Position of the error
-  * @param size
-  *   Size(in chars) of section to highlight
-  * @param errorContent
-  *   Contents of the file to generate code snippets
-  */
-def highlight(pos: Position, size: Int)(using errorContent: String, stdout: PrintStream): Unit = {
-  val lines = errorContent.split("\n")
-
-  val preLine = if (pos.line > 1) lines(pos.line - 2) else ""
-  val midLine = lines(pos.line - 1)
-  val postLine = if (pos.line < lines.size) lines(pos.line) else ""
-  val linePointer = " " * (pos.column + 2) + ("^" * (size)) + "\n"
-
-  stdout.println(
-    s"  >$preLine\n  >$midLine\n$linePointer  >$postLine"
-  )
-}
-
-/** Function to print the position of an error
-  *
-  * @param pos
-  *   Position of the error
-  */
-def printPosition(pos: Position)(using stdout: PrintStream): Unit = {
-  stdout.println(s"(line ${pos.line}, column ${pos.column}):")
+  /** Function to highlight a section of code for an error message
+    *
+    * @param pos
+    *   Position of the error
+    * @param size
+    *   Size(in chars) of section to highlight
+    */
+  def formatHighlight(pos: Position, size: Int): Unit = {
+    val lines = errorContent.split("\n")
+    val preLine = if (pos.line > 1) lines(pos.line - 2) else ""
+    val midLine = lines(pos.line - 1)
+    val postLine = if (pos.line < lines.size) lines(pos.line) else ""
+    val linePointer = " " * (pos.column + 2) + ("^" * (size)) + "\n"
+
+    sb.append(
+      s"  >$preLine\n  >$midLine\n$linePointer  >$postLine\netscape"
+    )
+  }
+
+  error match {
+    case Error.SyntaxError(_) =>
+      sb.append("Syntax error:\n")
+    case _ =>
+      sb.append("Semantic error:\n")
+  }
+
+  error match {
+    case Error.DuplicateDeclaration(ident) =>
+      formatPosition(ident.pos)
+      sb.append(s"Duplicate declaration of identifier ${ident.v}")
+      formatHighlight(ident.pos, ident.v.length)
+    case Error.UndeclaredVariable(ident) =>
+      formatPosition(ident.pos)
+      sb.append(s"Undeclared variable ${ident.v}")
+      formatHighlight(ident.pos, ident.v.length)
+    case Error.UndefinedFunction(ident) =>
+      formatPosition(ident.pos)
+      sb.append(s"Undefined function ${ident.v}")
+      formatHighlight(ident.pos, ident.v.length)
+    case Error.FunctionParamsMismatch(id, expected, got, funcType) =>
+      formatPosition(id.pos)
+      sb.append(s"Function expects $expected parameters, got $got")
+      sb.append(
+        s"(function ${id.v} has type (${funcType.params.mkString(", ")}) -> ${funcType.returnType})"
+      )
+      formatHighlight(id.pos, 1)
+    case Error.TypeMismatch(pos, expected, got, msg) =>
+      formatPosition(pos)
+      sb.append(s"Type mismatch: $msg\nExpected: $expected\nGot: $got")
+      formatHighlight(pos, 1)
+    case Error.SemanticError(pos, msg) =>
+      formatPosition(pos)
+      sb.append(msg)
+      formatHighlight(pos, 1)
+    case wacc.Error.InternalError(pos, msg) =>
+      formatPosition(pos)
+      sb.append(s"Internal error: $msg")
+      formatHighlight(pos, 1)
+    case Error.SyntaxError(msg) =>
+      sb.append(msg)
+      sb.append("\n")
+  }
+
+  sb.toString()
+
 }
diff --git a/src/main/wacc/frontend/ast.scala b/src/main/wacc/frontend/ast.scala
index ac0e585..9b14b13 100644
--- a/src/main/wacc/frontend/ast.scala
+++ b/src/main/wacc/frontend/ast.scala
@@ -4,7 +4,6 @@ import parsley.Parsley
 import parsley.generic.ErrorBridge
 import parsley.ap._
 import parsley.position._
-import parsley.syntax.zipped._
 import cats.data.NonEmptyList
 
 object ast {
diff --git a/src/test/wacc/examples.scala b/src/test/wacc/examples.scala
index 6114afd..11093d6 100644
--- a/src/test/wacc/examples.scala
+++ b/src/test/wacc/examples.scala
@@ -1,14 +1,19 @@
 package wacc
 
 import org.scalatest.BeforeAndAfterAll
-import org.scalatest.flatspec.AnyFlatSpec
 import org.scalatest.Inspectors.forEvery
+import org.scalatest.matchers.should.Matchers._
+import org.scalatest.freespec.AsyncFreeSpec
+import cats.effect.testing.scalatest.AsyncIOSpec
 import java.io.File
+import java.nio.file.Path
 import sys.process._
-import java.io.PrintStream
 import scala.io.Source
+import cats.effect.IO
+import wacc.{compile as compileWacc}
+
+class ParallelExamplesSpec extends AsyncFreeSpec with AsyncIOSpec with BeforeAndAfterAll {
 
-class ParallelExamplesSpec extends AnyFlatSpec with BeforeAndAfterAll {
   val files =
     allWaccFiles("wacc-examples/valid").map { p =>
       (p.toString, List(0))
@@ -23,95 +28,95 @@ class ParallelExamplesSpec extends AnyFlatSpec with BeforeAndAfterAll {
         (p.toString, List(100, 200))
       }
 
-  // tests go here
   forEvery(files) { (filename, expectedResult) =>
     val baseFilename = filename.stripSuffix(".wacc")
-    given stdout: PrintStream = PrintStream(File(baseFilename + ".out"))
 
-    s"$filename" should "be compiled with correct result" in {
-      val result = compile(filename)
-      assert(expectedResult.contains(result))
-    }
+    s"$filename" - {
+      "should be compiled with correct result" in {
+        compileWacc(Path.of(filename), outputDir = None, log = false).map { result =>
+          expectedResult should contain(result)
+        }
+      }
 
-    if (expectedResult == List(0)) it should "run with correct result" in {
-      if (fileIsDisallowedBackend(filename)) pending
+      if (expectedResult == List(0)) {
+        "should run with correct result" in {
+          if (fileIsDisallowedBackend(filename))
+            IO.pure(
+              succeed
+            ) // TODO: remove when advanced tests removed. not sure how to "pending" this otherwise
+          else {
+            for {
+              contents <- IO(Source.fromFile(File(filename)).getLines.toList)
+              inputLine = extractInput(contents)
+              expectedOutput = extractOutput(contents)
+              expectedExit = extractExit(contents)
 
-      // Retrieve contents to get input and expected output + exit code
-      val contents = scala.io.Source.fromFile(File(filename)).getLines.toList
-      val inputLine =
-        contents
-          .find(_.matches("^# ?[Ii]nput:.*$"))
-          .map(_.split(":").last.strip + "\n")
-          .getOrElse("")
-      val outputLineIdx = contents.indexWhere(_.matches("^# ?[Oo]utput:.*$"))
-      val expectedOutput =
-        if (outputLineIdx == -1) ""
-        else
-          contents
-            .drop(outputLineIdx + 1)
-            .takeWhile(_.startsWith("#"))
-            .map(_.stripPrefix("#").stripLeading)
-            .mkString("\n")
+              asmFilename = baseFilename + ".s"
+              execFilename = baseFilename
+              gccResult <- IO(s"gcc -o $execFilename -z noexecstack $asmFilename".!)
 
-      val exitLineIdx = contents.indexWhere(_.matches("^# ?[Ee]xit:.*$"))
-      val expectedExit =
-        if (exitLineIdx == -1) 0
-        else contents(exitLineIdx + 1).stripPrefix("#").strip.toInt
+              _ = assert(gccResult == 0)
 
-      // Assembly and link using gcc
-      val asmFilename = baseFilename + ".s"
-      val execFilename = baseFilename
-      val gccResult = s"gcc -o $execFilename -z noexecstack $asmFilename".!
-      assert(gccResult == 0)
+              stdout <- IO.pure(new StringBuilder)
+              process <- IO {
+                s"timeout 5s $execFilename" run ProcessIO(
+                  in = w => {
+                    w.write(inputLine.getBytes)
+                    w.close()
+                  },
+                  out = Source.fromInputStream(_).addString(stdout),
+                  err = _ => ()
+                )
+              }
 
-      // Run the executable with the provided input
-      val stdout = new StringBuilder
-      val process = s"timeout 5s $execFilename" run ProcessIO(
-        in = w => {
-          w.write(inputLine.getBytes)
-          w.close()
-        },
-        out = Source.fromInputStream(_).addString(stdout),
-        err = _ => ()
-      )
+              exitCode <- IO.pure(process.exitValue)
 
-      assert(process.exitValue == expectedExit)
-      assert(
-        stdout.toString
-          .replaceAll("0x[0-9a-f]+", "#addrs#")
-          .replaceAll("fatal error:.*", "#runtime_error#\u0000")
-          .takeWhile(_ != '\u0000')
-          == expectedOutput
-      )
+            } yield {
+              exitCode shouldBe expectedExit
+              normalizeOutput(stdout.toString) shouldBe expectedOutput
+            }
+          }
+        }
+      }
     }
   }
 
   def allWaccFiles(dir: String): IndexedSeq[os.Path] =
     val d = java.io.File(dir)
-    os.walk(os.Path(d.getAbsolutePath)).filter { _.ext == "wacc" }
+    os.walk(os.Path(d.getAbsolutePath)).filter(_.ext == "wacc")
 
+  // TODO: eventually remove this I think
   def fileIsDisallowedBackend(filename: String): Boolean =
     Seq(
-      // format: off
-      // disable formatting to avoid binPack
-      "^.*wacc-examples/valid/advanced.*$",
-      // "^.*wacc-examples/valid/array.*$",
-      // "^.*wacc-examples/valid/basic/exit.*$",
-      // "^.*wacc-examples/valid/basic/skip.*$",
-      // "^.*wacc-examples/valid/expressions.*$",
-      // "^.*wacc-examples/valid/function/nested_functions.*$",
-      // "^.*wacc-examples/valid/function/simple_functions.*$",
-      // "^.*wacc-examples/valid/if.*$",
-      // "^.*wacc-examples/valid/IO/print.*$",
-      // "^.*wacc-examples/valid/IO/read.*$",
-      // "^.*wacc-examples/valid/IO/IOLoop.wacc.*$",
-      // "^.*wacc-examples/valid/IO/IOSequence.wacc.*$",
-      // "^.*wacc-examples/valid/pairs.*$",
-      //"^.*wacc-examples/valid/runtimeErr.*$",
-      // "^.*wacc-examples/valid/scope.*$",
-      // "^.*wacc-examples/valid/sequence.*$",
-      // "^.*wacc-examples/valid/variables.*$",
-      // "^.*wacc-examples/valid/while.*$",
-      // format: on
-    ).find(filename.matches).isDefined
+      "^.*wacc-examples/valid/advanced.*$"
+    ).exists(filename.matches)
+
+  private def extractInput(contents: List[String]): String =
+    contents
+      .find(_.matches("^# ?[Ii]nput:.*$"))
+      .map(_.split(":").last.strip + "\n")
+      .getOrElse("")
+
+  private def extractOutput(contents: List[String]): String = {
+    val outputLineIdx = contents.indexWhere(_.matches("^# ?[Oo]utput:.*$"))
+    if (outputLineIdx == -1) ""
+    else
+      contents
+        .drop(outputLineIdx + 1)
+        .takeWhile(_.startsWith("#"))
+        .map(_.stripPrefix("#").stripLeading)
+        .mkString("\n")
+  }
+
+  private def extractExit(contents: List[String]): Int = {
+    val exitLineIdx = contents.indexWhere(_.matches("^# ?[Ee]xit:.*$"))
+    if (exitLineIdx == -1) 0
+    else contents(exitLineIdx + 1).stripPrefix("#").strip.toInt
+  }
+
+  private def normalizeOutput(output: String): String =
+    output
+      .replaceAll("0x[0-9a-f]+", "#addrs#")
+      .replaceAll("fatal error:.*", "#runtime_error#\u0000")
+      .takeWhile(_ != '\u0000')
 }