diff --git a/build.sbt b/build.sbt
index acf2e78a..359c5e20 100644
--- a/build.sbt
+++ b/build.sbt
@@ -8,7 +8,7 @@ def scala213 = "2.13.13"
 
 def scala212 = "2.12.19"
 
-def scala3 = "3.1.2"
+def scala3 = "3.3.3"
 def junitVersion = "4.13.2"
 def gcp = "com.google.cloud" % "google-cloud-storage" % "2.32.1"
 inThisBuild(
@@ -154,7 +154,16 @@ val sharedJVMSettings: List[Def.Setting[_]] = List(
 
 val sharedJSSettings: List[Def.Setting[_]] = List(
   skipIdeaSettings,
-  crossScalaVersions := allScalaVersions.filterNot(_.startsWith("0."))
+  crossScalaVersions := allScalaVersions.filterNot(_.startsWith("0.")),
+  scalacOptions ++= {
+    CrossVersion.partialVersion(scalaVersion.value) match {
+      case Some((2, _)) =>
+        List(
+          "-P:scalajs:nowarnGlobalExecutionContext",
+        )
+      case _ => Nil
+    }
+  }
 )
 val sharedJSConfigure: Project => Project =
   _.disablePlugins(MimaPlugin)
@@ -176,17 +185,40 @@ val sharedSettings = List(
           "-Ywarn-unused-import",
           "-target:jvm-1.8"
         )
-      case Some((major, _)) if major != 2 =>
+      case Some((2, 12)) =>
         List(
-          "-language:implicitConversions"
+          "-feature",
+          "-target:jvm-1.8",
+          "-Ywarn-unused-import",
+          "-Yrangepos"
+        )
+      case Some((2, _)) =>
+        List(
+          "-deprecation", // enable deprecation first because it sets -Wconf:cat=deprecation:w
+          "-feature",
+          "--release:8",
+          "-unchecked",
+          "-Wconf:cat=deprecation&origin=scala.collection.JavaConverters:s",
+          "-Wconf:cat=deprecation&origin=scala.reflect.api.Trees.New:s", // no quasiquotes
+          "-Wconf:cat=deprecation&origin=scala.reflect.api.Position.lineContent:s", // use it anyway
+          "-Wconf:msg=parameter:s", // quash other messages about unused parameters
+          "-Wunused:params",
+          //"-Wconf:cat=unused-privates&msg=never used:s",
+          //"-Wconf:cat=unused-params&msg=never used:s",
+          //"-Werror",
+          "-Xlint:-deprecation,_",
+          "-Yrangepos", // default
         )
       case _ =>
         List(
-          "-target:jvm-1.8",
-          "-Yrangepos",
-          // -Xlint is unusable because of
-          // https://github.com/scala/bug/issues/10448
-          "-Ywarn-unused:imports"
+          "-deprecation",
+          "-feature",
+          "-java-output-version:8",
+          "-Wconf:cat=deprecation&msg=Converters:s",
+          "-Wconf:cat=deprecation&msg=New:s", // no quasiquotes
+          "-Wconf:cat=deprecation&msg=Position:s",
+          //"-Wunused:all",
+          //"-language:implicitConversions"
         )
     }
   }
diff --git a/docs/tests.md b/docs/tests.md
index eaa2651a..45cf768b 100644
--- a/docs/tests.md
+++ b/docs/tests.md
@@ -237,7 +237,7 @@ def check[T](
 
 check("basic", List(1, 2), Some(1))
 check("empty", List(), Some(1))
-check("null", List(null, 2), Some(null))
+check("null", List(null, "more"), Some(null))
 ```
 
 When declaring tests in a helper function, it's useful to pass around an
diff --git a/munit-scalacheck/shared/src/main/scala/munit/ScalaCheckSuite.scala b/munit-scalacheck/shared/src/main/scala/munit/ScalaCheckSuite.scala
index 0efa550b..a7a07dd2 100644
--- a/munit-scalacheck/shared/src/main/scala/munit/ScalaCheckSuite.scala
+++ b/munit-scalacheck/shared/src/main/scala/munit/ScalaCheckSuite.scala
@@ -1,9 +1,12 @@
 package munit
 
+import language.implicitConversions
+
 import org.scalacheck.Prop
 import org.scalacheck.{Test => ScalaCheckTest}
 import org.scalacheck.util.Pretty
 import org.scalacheck.rng.Seed
+import scala.annotation.nowarn
 import scala.util.Success
 import scala.util.Failure
 import scala.util.Try
@@ -25,6 +28,7 @@ trait ScalaCheckSuite extends FunSuite {
   // Allow property bodies of type Unit
   // This is done to support using MUnit assertions in property bodies
   // instead of returning a Boolean.
+  @nowarn("msg=used")
   implicit def unitToProp(unit: Unit): Prop = Prop.passed
 
   override def munitTestTransforms: List[TestTransform] =
diff --git a/munit/js-native/src/main/scala/munit/internal/junitinterface/JUnitReporter.scala b/munit/js-native/src/main/scala/munit/internal/junitinterface/JUnitReporter.scala
index a65fdefc..7a26d33f 100644
--- a/munit/js-native/src/main/scala/munit/internal/junitinterface/JUnitReporter.scala
+++ b/munit/js-native/src/main/scala/munit/internal/junitinterface/JUnitReporter.scala
@@ -7,6 +7,7 @@ package munit.internal.junitinterface
 import munit.internal.console.AnsiColors
 import sbt.testing._
 import munit.internal.PlatformCompat
+import scala.annotation.nowarn
 
 final class JUnitReporter(
     eventHandler: EventHandler,
@@ -35,6 +36,7 @@ final class JUnitReporter(
     }
     emitEvent(method, Status.Ignored)
   }
+  @nowarn("msg=used")
   def reportAssumptionViolation(
       method: String,
       timeInSeconds: Double,
@@ -219,6 +221,7 @@ final class JUnitReporter(
       .map(_.getFileName)
       .orNull
 
+  @nowarn("msg=used")
   private def stackTraceElementToString(
       e: StackTraceElement,
       testFileName: String
diff --git a/munit/js-native/src/main/scala/munit/internal/junitinterface/JUnitRunner.scala b/munit/js-native/src/main/scala/munit/internal/junitinterface/JUnitRunner.scala
index 59cef135..94a13cff 100644
--- a/munit/js-native/src/main/scala/munit/internal/junitinterface/JUnitRunner.scala
+++ b/munit/js-native/src/main/scala/munit/internal/junitinterface/JUnitRunner.scala
@@ -6,7 +6,9 @@ package munit.internal.junitinterface
 
 import sbt.testing._
 import munit.internal.PlatformCompat
+import scala.annotation.nowarn
 
+@nowarn("msg=used")
 final class JUnitRunner(
     val args: Array[String],
     _remoteArgs: Array[String],
diff --git a/munit/js-native/src/main/scala/org/junit/experimental/categories/Category.scala b/munit/js-native/src/main/scala/org/junit/experimental/categories/Category.scala
index ef674c8c..1b2b27fd 100644
--- a/munit/js-native/src/main/scala/org/junit/experimental/categories/Category.scala
+++ b/munit/js-native/src/main/scala/org/junit/experimental/categories/Category.scala
@@ -1,5 +1,7 @@
 package org.junit.experimental.categories
 
 import scala.annotation.Annotation
+import scala.annotation.nowarn
 
+@nowarn("msg=used")
 class Category(classes: Array[Class[_]]) extends Annotation
diff --git a/munit/js-native/src/main/scala/org/junit/runner/RunWith.scala b/munit/js-native/src/main/scala/org/junit/runner/RunWith.scala
index 26c8bd84..77d908f5 100644
--- a/munit/js-native/src/main/scala/org/junit/runner/RunWith.scala
+++ b/munit/js-native/src/main/scala/org/junit/runner/RunWith.scala
@@ -1,5 +1,7 @@
 package org.junit.runner
 
 import scala.annotation.Annotation
+import scala.annotation.nowarn
 
+@nowarn("msg=used")
 class RunWith(cls: Class[_]) extends Annotation
diff --git a/munit/js/src/main/scala/munit/internal/PlatformCompat.scala b/munit/js/src/main/scala/munit/internal/PlatformCompat.scala
index b5ed7e24..8ad9ba36 100644
--- a/munit/js/src/main/scala/munit/internal/PlatformCompat.scala
+++ b/munit/js/src/main/scala/munit/internal/PlatformCompat.scala
@@ -3,10 +3,11 @@ package munit.internal
 import scala.scalajs.reflect.Reflect
 import sbt.testing.TaskDef
 import munit.MUnitRunner
-import scala.concurrent.Future
 import sbt.testing.Task
 import sbt.testing.EventHandler
 import sbt.testing.Logger
+import scala.annotation.nowarn
+import scala.concurrent.Future
 import scala.concurrent.Promise
 import scala.concurrent.duration.Duration
 import scala.concurrent.Await
@@ -36,7 +37,7 @@ object PlatformCompat {
       ec: ExecutionContext
   ): Future[T] = {
     val onComplete = Promise[T]()
-    val timeoutHandle = timers.setTimeout(duration.toMillis) {
+    val timeoutHandle = timers.setTimeout(duration.toMillis.toDouble) {
       onComplete.tryFailure(
         new TimeoutException(s"test timed out after $duration")
       )
@@ -65,6 +66,7 @@ object PlatformCompat {
   def isJS: Boolean = true
   def isNative: Boolean = false
 
+  @nowarn("msg=used")
   def newRunner(
       taskDef: TaskDef,
       classLoader: ClassLoader
diff --git a/munit/native/src/main/scala/munit/internal/PlatformCompat.scala b/munit/native/src/main/scala/munit/internal/PlatformCompat.scala
index 9ddbd8e3..e6b1f481 100644
--- a/munit/native/src/main/scala/munit/internal/PlatformCompat.scala
+++ b/munit/native/src/main/scala/munit/internal/PlatformCompat.scala
@@ -7,6 +7,7 @@ import scala.scalanative.reflect.Reflect
 import sbt.testing.Task
 import sbt.testing.EventHandler
 import sbt.testing.Logger
+import scala.annotation.nowarn
 import scala.concurrent.Await
 import scala.concurrent.Awaitable
 import scala.concurrent.duration.Duration
@@ -26,6 +27,7 @@ object PlatformCompat {
     task.execute(eventHandler, loggers)
     Future.successful(())
   }
+  @nowarn("msg=used")
   def waitAtMost[T](
       startFuture: () => Future[T],
       duration: Duration,
@@ -47,6 +49,7 @@ object PlatformCompat {
   def isJS: Boolean = false
   def isNative: Boolean = true
 
+  @nowarn("msg=used")
   def newRunner(
       taskDef: TaskDef,
       classLoader: ClassLoader
diff --git a/munit/native/src/main/scala/munit/internal/junitinterface/JUnitTask.scala b/munit/native/src/main/scala/munit/internal/junitinterface/JUnitTask.scala
index 791ae277..5b50b959 100644
--- a/munit/native/src/main/scala/munit/internal/junitinterface/JUnitTask.scala
+++ b/munit/native/src/main/scala/munit/internal/junitinterface/JUnitTask.scala
@@ -7,7 +7,6 @@ package munit.internal.junitinterface
 import munit.internal.PlatformCompat
 import org.junit.runner.notification.RunNotifier
 import sbt.testing._
-import scala.concurrent.ExecutionContext.Implicits.global
 
 /* Implementation note: In JUnitTask we use Future[Try[Unit]] instead of simply
  * Future[Unit]. This is to prevent Scala's Future implementation to box/wrap
diff --git a/munit/shared/src/main/scala-2.13/munit/internal/Compat.scala b/munit/shared/src/main/scala-2.13/munit/internal/Compat.scala
index e0606348..29cd3dac 100644
--- a/munit/shared/src/main/scala-2.13/munit/internal/Compat.scala
+++ b/munit/shared/src/main/scala-2.13/munit/internal/Compat.scala
@@ -1,5 +1,7 @@
 package munit.internal
 
+import language.reflectiveCalls
+
 object Compat {
   type LazyList[+T] = scala.LazyList[T]
   val LazyList = scala.LazyList
diff --git a/munit/shared/src/main/scala-2/munit/internal/MacroCompat.scala b/munit/shared/src/main/scala-2/munit/internal/MacroCompat.scala
index 594abdb7..eb81e0f1 100644
--- a/munit/shared/src/main/scala-2/munit/internal/MacroCompat.scala
+++ b/munit/shared/src/main/scala-2/munit/internal/MacroCompat.scala
@@ -2,6 +2,7 @@ package munit.internal
 
 import munit.Clue
 import munit.Location
+import scala.language.implicitConversions
 import scala.language.experimental.macros
 import scala.reflect.macros.blackbox.Context
 
diff --git a/munit/shared/src/main/scala-3/munit/internal/MacroCompat.scala b/munit/shared/src/main/scala-3/munit/internal/MacroCompat.scala
index 721cf52b..8b5a4668 100644
--- a/munit/shared/src/main/scala-3/munit/internal/MacroCompat.scala
+++ b/munit/shared/src/main/scala-3/munit/internal/MacroCompat.scala
@@ -4,6 +4,7 @@ import munit.Clue
 import munit.Location
 import scala.quoted._
 import scala.language.experimental.macros
+import scala.language.implicitConversions
 
 object MacroCompat {
 
@@ -15,7 +16,7 @@ object MacroCompat {
   def locationImpl()(using Quotes): Expr[Location] = {
     import quotes.reflect._
     val pos = Position.ofMacroExpansion
-    val path = pos.sourceFile.jpath.toString
+    val path = pos.sourceFile.path
     val startLine = pos.startLine + 1
     '{ new Location(${ Expr(path) }, ${ Expr(startLine) }) }
   }
diff --git a/munit/shared/src/main/scala/munit/Assertions.scala b/munit/shared/src/main/scala/munit/Assertions.scala
index fea92e7a..cec77f8b 100644
--- a/munit/shared/src/main/scala/munit/Assertions.scala
+++ b/munit/shared/src/main/scala/munit/Assertions.scala
@@ -4,9 +4,10 @@ import munit.internal.console.{Lines, Printers, StackTraces}
 import munit.internal.difflib.ComparisonFailExceptionHandler
 import munit.internal.difflib.Diffs
 
+import scala.annotation.nowarn
+import scala.collection.mutable
 import scala.reflect.ClassTag
 import scala.util.control.NonFatal
-import scala.collection.mutable
 import munit.internal.console.AnsiColors
 import org.junit.AssumptionViolatedException
 import munit.internal.MacroCompat
@@ -37,7 +38,7 @@ trait Assertions extends MacroCompat.CompileErrorMacro {
   def assume(
       cond: Boolean,
       clue: => Any = "assumption failed"
-  )(implicit loc: Location): Unit = {
+  )(implicit @nowarn loc: Location): Unit = {
     StackTraces.dropInside {
       if (!cond) {
         throw new AssumptionViolatedException(munitPrint(clue))
@@ -95,7 +96,7 @@ trait Assertions extends MacroCompat.CompileErrorMacro {
     StackTraces.dropInside {
       if (!compare.isEqual(obtained, expected)) {
         (obtained, expected) match {
-          case (a: Array[_], b: Array[_]) if a.sameElements(b) =>
+          case (a: Array[_], b: Array[_]) if a.sameElements[Any](b) =>
             // Special-case error message when comparing arrays. See
             // https://github.com/scalameta/munit/pull/393 and
             // https://github.com/scalameta/munit/issues/339 for a related
diff --git a/munit/shared/src/main/scala/munit/MUnitRunner.scala b/munit/shared/src/main/scala/munit/MUnitRunner.scala
index 348d79b3..c997b4f5 100644
--- a/munit/shared/src/main/scala/munit/MUnitRunner.scala
+++ b/munit/shared/src/main/scala/munit/MUnitRunner.scala
@@ -15,6 +15,7 @@ import org.junit.runner.notification.Failure
 import org.junit.runner.notification.RunNotifier
 
 import java.lang.reflect.Modifier
+import scala.annotation.nowarn
 import scala.collection.mutable
 import scala.concurrent.ExecutionContext
 import scala.concurrent.Future
@@ -29,7 +30,7 @@ class MUnitRunner(val cls: Class[_ <: Suite], newInstance: () => Suite)
     with Configurable {
 
   def this(cls: Class[_ <: Suite]) =
-    this(MUnitRunner.ensureEligibleConstructor(cls), () => cls.newInstance())
+    this(MUnitRunner.ensureEligibleConstructor(cls), () => cls.getDeclaredConstructor().newInstance())
 
   val suite: Suite = newInstance()
 
@@ -92,7 +93,7 @@ class MUnitRunner(val cls: Class[_ <: Suite], newInstance: () => Suite)
         val desc = Description.createTestDescription(
           cls,
           testName,
-          test.annotations: _*
+          test.annotations.toIndexedSeq: _*
         )
         desc
       }
@@ -168,6 +169,7 @@ class MUnitRunner(val cls: Class[_ <: Suite], newInstance: () => Suite)
     loop(futures, mutable.ListBuffer.empty)
   }
 
+  @nowarn
   private def munitTimeout(): Option[Duration] = {
     suite match {
       case funSuite: FunSuite => Some(funSuite.munitTimeout)
@@ -245,7 +247,6 @@ class MUnitRunner(val cls: Class[_ <: Suite], newInstance: () => Suite)
       test: Test
   ): Future[BeforeAllResult] = {
     val context = new BeforeEach(test)
-    val fixtures = mutable.ListBuffer.empty[AnyFixture[_]]
     sequenceFutures(
       munitFixtures.iterator.map(f =>
         valueTransform(() => f.beforeEach(context)).map(_ => f)
diff --git a/munit/shared/src/main/scala/munit/TestOptions.scala b/munit/shared/src/main/scala/munit/TestOptions.scala
index 6b958133..d2243bf8 100644
--- a/munit/shared/src/main/scala/munit/TestOptions.scala
+++ b/munit/shared/src/main/scala/munit/TestOptions.scala
@@ -46,6 +46,8 @@ object TestOptions extends TestOptionsConversions {
 
 trait TestOptionsConversions {
 
+  import language.implicitConversions
+
   /**
    * Implicitly create a TestOptions given a test name.
    * This allows writing `test("name") { ... }` even if `test` accepts a `TestOptions`
diff --git a/munit/shared/src/main/scala/munit/ValueTransforms.scala b/munit/shared/src/main/scala/munit/ValueTransforms.scala
index d6a3bea2..6e57659b 100644
--- a/munit/shared/src/main/scala/munit/ValueTransforms.scala
+++ b/munit/shared/src/main/scala/munit/ValueTransforms.scala
@@ -26,7 +26,7 @@ trait ValueTransforms { this: BaseFunSuite =>
       val nested: Future[Future[Any]] = future.map { value =>
         val transformed = munitValueTransforms.iterator
           .map(fn => fn(value))
-          .collectFirst { case Some(future) => future }
+          .collectFirst { case Some(f) => f }
         transformed match {
           case Some(f) => flattenFuture(f)
           case None    => Future.successful(value)
diff --git a/munit/shared/src/main/scala/munit/internal/FutureCompat.scala b/munit/shared/src/main/scala/munit/internal/FutureCompat.scala
index 1581f51e..3c4fbcd0 100644
--- a/munit/shared/src/main/scala/munit/internal/FutureCompat.scala
+++ b/munit/shared/src/main/scala/munit/internal/FutureCompat.scala
@@ -1,8 +1,8 @@
 package munit.internal
 
+import scala.concurrent.ExecutionContext
 import scala.concurrent.Future
 import scala.util.Try
-import scala.concurrent.ExecutionContext
 
 object FutureCompat {
   implicit class ExtensionFuture[T](f: Future[T]) {
diff --git a/munit/shared/src/main/scala/munit/internal/difflib/Diffs.scala b/munit/shared/src/main/scala/munit/internal/difflib/Diffs.scala
index a8c983dd..e17e1123 100644
--- a/munit/shared/src/main/scala/munit/internal/difflib/Diffs.scala
+++ b/munit/shared/src/main/scala/munit/internal/difflib/Diffs.scala
@@ -7,7 +7,7 @@ object Diffs {
   def create(obtained: String, expected: String): Diff =
     new Diff(obtained, expected)
 
-  @deprecated("")
+  @deprecated("", since="")
   def assertNoDiff(
       obtained: String,
       expected: String,
diff --git a/munit/shared/src/main/scala/munit/internal/difflib/Equalizer.scala b/munit/shared/src/main/scala/munit/internal/difflib/Equalizer.scala
index 4c5037b5..623612af 100644
--- a/munit/shared/src/main/scala/munit/internal/difflib/Equalizer.scala
+++ b/munit/shared/src/main/scala/munit/internal/difflib/Equalizer.scala
@@ -6,7 +6,7 @@ trait Equalizer[T] {
 object Equalizer {
   def default[T]: Equalizer[T] = new Equalizer[T] {
     override def equals(original: T, revised: T): Boolean = {
-      original.equals(revised)
+      original == revised   //original.equals(revised)
     }
   }
 }
diff --git a/tests/jvm/src/test/scala/munit/AsyncFunFixtureOrderSuite.scala b/tests/jvm/src/test/scala/munit/AsyncFunFixtureOrderSuite.scala
index c6eda50b..a1fedd9d 100644
--- a/tests/jvm/src/test/scala/munit/AsyncFunFixtureOrderSuite.scala
+++ b/tests/jvm/src/test/scala/munit/AsyncFunFixtureOrderSuite.scala
@@ -4,7 +4,7 @@ import scala.concurrent.Future
 import scala.concurrent.Promise
 
 class AsyncFunFixtureOrderSuite extends FunSuite {
-  val latch: Promise[Unit] = Promise[Unit]
+  val latch: Promise[Unit] = Promise[Unit]()
   var completedFromTest: Option[Boolean] = None
   var completedFromTeardown: Option[Boolean] = None
 
diff --git a/tests/shared/src/test/scala/munit/PrintersSuite.scala b/tests/shared/src/test/scala/munit/PrintersSuite.scala
index 4a692af4..7e02abd2 100644
--- a/tests/shared/src/test/scala/munit/PrintersSuite.scala
+++ b/tests/shared/src/test/scala/munit/PrintersSuite.scala
@@ -63,7 +63,7 @@ class PrintersSuite extends FunSuite { self =>
 
   check(
     "list",
-    List(1, 2, 3, List(4, 5, List(6, 7))),
+    List[Any](1, 2, 3, List[Any](4, 5, List(6, 7))),
     """|List(
        |  1,
        |  2,