diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index a3920f7de..6f3ce0146 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -21,17 +21,11 @@ jobs:
       - name: Setup Scala
         uses: japgolly/setup-everything-scala@v1.0
 
-      - name: Build
-        run: sbt -DCI=1 "++${{ matrix.scalaversion }}" package
-
-      - name: Test generate documentation
-        run: sbt -DCI=1 "++${{ matrix.scalaversion }}" doc
-
-      - name: Build examples
-        run: sbt -DCI=1 "++${{ matrix.scalaversion }}" example/compile
+      - name: Build and test
+        run: sbt -DCI=1 "++${{ matrix.scalaversion }}" test package doc
 
       - name: Validate formatting
-        run: sbt -DCI=1 "++${{ matrix.scalaversion }}" scalafmtCheck
+        run: sbt -DCI=1 "++${{ matrix.scalaversion }}" dom/scalafmtCheck
 
       - name: Validate api report
         if: matrix.scalaversion != '2.11.12' && matrix.scalaversion != '3.0.1'
diff --git a/build.sbt b/build.sbt
index 0d18f1e6b..6f7a9e27e 100644
--- a/build.sbt
+++ b/build.sbt
@@ -4,8 +4,16 @@ ThisBuild / organization  := "org.scala-js"
 ThisBuild / shellPrompt   := ((s: State) => Project.extract(s).currentRef.project + "> ")
 ThisBuild / versionScheme := Some("early-semver")
 
-val root          = Build.root
-val scalafixRules = Build.scalafixRules
-val dom           = Build.dom
-val example       = Build.example
-val readme        = Build.readme
+val root           = Build.root
+val scalafixRules  = Build.scalafixRules
+val dom            = Build.dom
+val testsShared    = Build.testsShared
+val testsWebworker = Build.testsWebworker
+val testsChrome    = Build.testsChrome
+val testsFirefox   = Build.testsFirefox
+val testsNodeJsdom = Build.testsNodeJsdom
+val example        = Build.example
+val readme         = Build.readme
+
+// TODO: Remove after dom project get it's own directory
+Global / onLoad ~= (_.andThen("project root" :: _))
diff --git a/prePR.sbt b/prePR.sbt
index 515fae1d5..d5ecb479a 100644
--- a/prePR.sbt
+++ b/prePR.sbt
@@ -4,8 +4,21 @@ addCommandAlias("prePR", "+prePR_nonCross")
 
 val prePR_nonCross = taskKey[Unit]("Performs all necessary work required before submitting a PR, for a single version of Scala.")
 
+// Unfortunately we can't just call `root/Test/compile` because it doesn't take aggregation into account :(
 ThisBuild / prePR_nonCross := Def.sequential(
-  root / clean,
+
+  Def.task {
+    (root           / clean).value
+    (scalafixRules  / clean).value
+    (dom            / clean).value
+    (testsShared    / clean).value
+    (testsWebworker / clean).value
+    (testsChrome    / clean).value
+    (testsFirefox   / clean).value
+    (testsNodeJsdom / clean).value
+    (example        / clean).value
+  },
+
   dom / Compile / scalafmt,
   Def.taskDyn {
     if (scalaVersion.value.startsWith("2."))
@@ -13,5 +26,21 @@ ThisBuild / prePR_nonCross := Def.sequential(
     else
       Def.task[Unit]((dom / Compile / compile).value)
   },
-  root / Compile / compile,
+
+  Def.task {
+    (testsShared    / Test / compile).value
+    (testsWebworker / Test / compile).value
+    (testsChrome    / Test / compile).value
+    (testsFirefox   / Test / compile).value
+    (testsNodeJsdom / Test / compile).value
+    (example        / Test / compile).value
+  },
+
+  Def.taskDyn {
+    if (scalaVersion.value.startsWith("2.12."))
+      Def.task[Unit]((readme / Compile / compile).value)
+    else
+      Def.task(())
+  },
+
 ).value
diff --git a/project/Build.scala b/project/Build.scala
index de90efa55..bf249b7d4 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -1,7 +1,17 @@
 import sbt._
 import sbt.Keys._
+import java.util.concurrent.TimeUnit
+import org.openqa.selenium.{Capabilities, WebDriver}
+import org.openqa.selenium.chrome.{ChromeDriver, ChromeOptions}
+import org.openqa.selenium.firefox.{FirefoxOptions, FirefoxProfile}
+import org.openqa.selenium.remote.server.{DriverFactory, DriverProvider}
+import org.scalajs.jsenv.jsdomnodejs.JSDOMNodeJSEnv
+import org.scalajs.jsenv.selenium.SeleniumJSEnv
+import org.scalajs.sbtplugin.ScalaJSJUnitPlugin
 import org.scalajs.sbtplugin.ScalaJSPlugin
 import org.scalajs.sbtplugin.ScalaJSPlugin.autoImport._
+import sbtbuildinfo.BuildInfoPlugin
+import sbtbuildinfo.BuildInfoPlugin.autoImport._
 import scalafix.sbt.ScalafixPlugin
 import scalafix.sbt.ScalafixPlugin.autoImport._
 import scalatex.ScalatexReadme
@@ -21,6 +31,11 @@ object Build {
     .aggregate(
       scalafixRules,
       dom,
+      testsShared,
+      testsWebworker,
+      testsChrome,
+      testsFirefox,
+      testsNodeJsdom,
       example,
       // readme, // This is a Scala 2.12 only module
     )
@@ -43,6 +58,85 @@ object Build {
       libraryDependencies += Dep.scalafixCore.value,
     )
 
+  lazy val testsShared = project
+    .in(file("tests-shared"))
+    .dependsOn(dom)
+    .enablePlugins(ScalaJSPlugin, ScalaJSJUnitPlugin)
+    .configure(commonSettings, crossScala, preventPublication, moveTestLibsToCompile)
+
+  lazy val testsWebworker = project
+    .in(file("tests-webworker"))
+    .dependsOn(testsShared)
+    .enablePlugins(ScalaJSPlugin, ScalaJSJUnitPlugin, BuildInfoPlugin)
+    .configure(commonSettings, crossScala, preventPublication, moveTestLibsToCompile)
+    .settings(
+      buildInfoKeys := Seq[BuildInfoKey](
+        "wwJsPath" -> (Compile / fastOptJS / artifactPath).value.absolutePath,
+      ),
+      buildInfoPackage := "org.scalajs.dom.tests.webworker",
+      scalaJSUseMainModuleInitializer := true,
+    )
+
+  def testsWebworkers: Project => Project = _
+    .dependsOn(testsWebworker)
+    .settings(
+      Test / test := {
+        val _ = (testsWebworker / Compile / fastOptJS).value
+        (Test / test).value
+      },
+    )
+
+  lazy val testsChrome = project
+    .in(file("tests-chrome"))
+    .dependsOn(testsShared % Test)
+    .enablePlugins(ScalaJSPlugin, ScalaJSJUnitPlugin)
+    .configure(commonSettings, crossScala, preventPublication, testsWebworkers)
+    .settings(
+      Test / jsEnv := {
+        System.setProperty("webdriver.chrome.silentOutput", "true")
+        val o = new ChromeOptions()
+        o.setHeadless(true)
+        o.addArguments("--allow-file-access-from-files")
+        val df = new DriverFactory {
+          private[this] val default = SeleniumJSEnv.Config().driverFactory
+          override def newInstance(c: Capabilities): WebDriver = {
+            val d = default.newInstance(c).asInstanceOf[ChromeDriver]
+            d.manage.timeouts.pageLoadTimeout(if (inCI) 10 else 1, TimeUnit.MINUTES)
+            d.manage.timeouts.setScriptTimeout(if (inCI) 10 else 1, TimeUnit.MINUTES)
+            d
+          }
+          override def registerDriverProvider(p: DriverProvider): Unit =
+            default.registerDriverProvider(p)
+        }
+        new SeleniumJSEnv(o, SeleniumJSEnv.Config().withDriverFactory(df))
+      },
+    )
+
+  lazy val testsFirefox = project
+    .in(file("tests-firefox"))
+    .dependsOn(testsShared % Test)
+    .enablePlugins(ScalaJSPlugin, ScalaJSJUnitPlugin)
+    .configure(commonSettings, crossScala, preventPublication, testsWebworkers)
+    .settings(
+      Test / jsEnv := {
+        val p = new FirefoxProfile()
+        p.setPreference("privacy.file_unique_origin", false)
+        val o = new FirefoxOptions()
+        o.setProfile(p)
+        o.setHeadless(true)
+        new SeleniumJSEnv(o)
+      },
+    )
+
+  lazy val testsNodeJsdom = project
+    .in(file("tests-node-jsdom"))
+    .dependsOn(testsShared % Test)
+    .enablePlugins(ScalaJSPlugin, ScalaJSJUnitPlugin)
+    .configure(commonSettings, crossScala, preventPublication)
+    .settings(
+      Test / jsEnv := new JSDOMNodeJSEnv,
+    )
+
   lazy val example = project
     .dependsOn(dom)
     .enablePlugins(ScalaJSPlugin)
diff --git a/project/Lib.scala b/project/Lib.scala
index 26727423e..9ff78c465 100644
--- a/project/Lib.scala
+++ b/project/Lib.scala
@@ -1,5 +1,6 @@
 import sbt._
 import sbt.Keys._
+import org.scalajs.sbtplugin.ScalaJSJUnitPlugin
 import Dependencies._
 
 object Lib {
@@ -22,6 +23,7 @@ object Lib {
         case Some((2, 13)) => "-Wunused:imports,patvars,locals,implicits" :: Nil
         case _             => Nil
       }),
+      testOptions += Tests.Argument(TestFramework("com.novocode.junit.JUnitFramework"), "-v"),
     )
 
   def crossScala: Project => Project = _
@@ -100,4 +102,13 @@ object Lib {
     else
       sourceDir / "scala-old-collections"
 
+  def moveTestLibsToCompile: Project => Project =
+    _.settings(
+      libraryDependencies ~= { _.map(m =>
+        if (m.configurations.contains(Test.name))
+          m.withConfigurations(Some(Compile.name))
+        else
+          m
+      )},
+    )
 }
diff --git a/project/plugins.sbt b/project/plugins.sbt
index 51e7424b4..4cc950a7a 100644
--- a/project/plugins.sbt
+++ b/project/plugins.sbt
@@ -1,4 +1,8 @@
+libraryDependencies += "org.scala-js" %% "scalajs-env-jsdom-nodejs" % "1.1.0"
+libraryDependencies += "org.scala-js" %% "scalajs-env-selenium"     % "1.1.1"
+
 addSbtPlugin("ch.epfl.scala" % "sbt-scalafix"        % "0.9.30")
+addSbtPlugin("com.eed3si9n"  % "sbt-buildinfo"       % "0.10.0")
 addSbtPlugin("com.geirsson"  % "sbt-ci-release"      % "1.5.7")
 addSbtPlugin("com.lihaoyi"   % "scalatex-sbt-plugin" % "0.3.11")
 addSbtPlugin("org.scala-js"  % "sbt-scalajs"         % "1.5.1")
diff --git a/tests-chrome/src/test/scala/org/scalajs/dom/tests/chrome/ChromeTests.scala b/tests-chrome/src/test/scala/org/scalajs/dom/tests/chrome/ChromeTests.scala
new file mode 100644
index 000000000..9a4e5e267
--- /dev/null
+++ b/tests-chrome/src/test/scala/org/scalajs/dom/tests/chrome/ChromeTests.scala
@@ -0,0 +1,6 @@
+package org.scalajs.dom.tests.chrome
+
+import org.scalajs.dom.tests.shared._
+import org.scalajs.dom.tests.webworker._
+
+class ChromeTests extends SharedTests with WebWorkerTests
\ No newline at end of file
diff --git a/tests-firefox/src/test/scala/org/scalajs/dom/tests/firefox/FirefoxTests.scala b/tests-firefox/src/test/scala/org/scalajs/dom/tests/firefox/FirefoxTests.scala
new file mode 100644
index 000000000..1a8735389
--- /dev/null
+++ b/tests-firefox/src/test/scala/org/scalajs/dom/tests/firefox/FirefoxTests.scala
@@ -0,0 +1,6 @@
+package org.scalajs.dom.tests.firefox
+
+import org.scalajs.dom.tests.shared._
+import org.scalajs.dom.tests.webworker._
+
+class FirefoxTests extends SharedTests with WebWorkerTests
\ No newline at end of file
diff --git a/tests-node-jsdom/src/test/scala/org/scalajs/dom/tests/node/jsdom/NodeJsdomTests.scala b/tests-node-jsdom/src/test/scala/org/scalajs/dom/tests/node/jsdom/NodeJsdomTests.scala
new file mode 100644
index 000000000..47d280102
--- /dev/null
+++ b/tests-node-jsdom/src/test/scala/org/scalajs/dom/tests/node/jsdom/NodeJsdomTests.scala
@@ -0,0 +1,5 @@
+package org.scalajs.dom.tests.node.jsdom
+
+import org.scalajs.dom.tests.shared._
+
+class NodeJsdomTests extends SharedTests
diff --git a/tests-shared/src/main/scala/org/scalajs/dom/tests/shared/AsyncTesting.scala b/tests-shared/src/main/scala/org/scalajs/dom/tests/shared/AsyncTesting.scala
new file mode 100644
index 000000000..2a1646097
--- /dev/null
+++ b/tests-shared/src/main/scala/org/scalajs/dom/tests/shared/AsyncTesting.scala
@@ -0,0 +1,37 @@
+package org.scalajs.dom.tests.shared
+
+import org.junit.Assert
+import scala.concurrent._
+import scala.util._
+import scala.scalajs.js.timers._
+
+object AsyncTesting {
+
+  type AsyncResult = Future[Try[Unit]]
+
+  implicit def global: ExecutionContext =
+    ExecutionContext.global
+
+  def async(run: => Future[Any]): AsyncResult = {
+    val p = Promise[Try[Unit]]()
+    val timeout = setTimeout(1200) {
+      p.tryComplete(Failure(new RuntimeException("Test timed out.")))
+    }
+    setTimeout(1) {
+      run.onComplete { ta =>
+        clearTimeout(timeout)
+        p.complete(Success(ta.map(_ => ())))
+      }
+    }
+    p.future
+  }
+
+  implicit final class AsyncFutureOps[A](private val self: Future[A]) extends AnyVal {
+    def tap(f: A => Any): Future[A] =
+      self.map { a => f(a); a }
+
+    def assertEquals(expect: A): Future[A] =
+      tap(Assert.assertEquals(expect, _))
+  }
+
+}
diff --git a/tests-shared/src/main/scala/org/scalajs/dom/tests/shared/SharedTests.scala b/tests-shared/src/main/scala/org/scalajs/dom/tests/shared/SharedTests.scala
new file mode 100644
index 000000000..48abbe9c4
--- /dev/null
+++ b/tests-shared/src/main/scala/org/scalajs/dom/tests/shared/SharedTests.scala
@@ -0,0 +1,31 @@
+package org.scalajs.dom.tests.shared
+
+import java.util.UUID
+import org.junit.Test
+import org.scalajs.dom._
+import org.scalajs.dom.raw._
+
+trait SharedTests {
+  import SharedTests._
+
+  // https://github.com/scala-js/scala-js-dom/issues/411 - console doesn't work in web workers
+  @Test final def ConsoleLogTest(): Unit =
+    console.log("Testing console.log")
+
+  // https://github.com/scala-js/scala-js-dom/pull/432 - Avoid forcing evaluation of crypto
+  @Test final def CryptoNonStrictTest(): Unit = {
+    val _ = crypto.HashAlgorithm
+  }
+
+  @Test final def WindowIdbTest(): Unit =
+    window.indexedDB.foreach(testIdb)
+
+}
+
+object SharedTests {
+  def testIdb(idb: IDBFactory): Unit = {
+    val open = idb.open(UUID.randomUUID().toString())
+    open.onerror = (e: Event) => sys.error("idb open failed: " + e)
+    // TODO: Test properly in a different PR
+  }
+}
diff --git a/tests-webworker/src/main/scala/org/scalajs/dom/tests/webworker/Client.scala b/tests-webworker/src/main/scala/org/scalajs/dom/tests/webworker/Client.scala
new file mode 100644
index 000000000..614e61c58
--- /dev/null
+++ b/tests-webworker/src/main/scala/org/scalajs/dom/tests/webworker/Client.scala
@@ -0,0 +1,43 @@
+package org.scalajs.dom.tests.webworker
+
+import org.scalajs.dom.raw._
+import scala.concurrent._
+import scala.scalajs.js
+import scala.util.Success
+
+final class Client(worker: Worker) {
+  import Protocol._
+
+  private var preInit  = new js.Array[Message]
+  private var promises = new js.Array[Promise[String]]
+
+  worker.onmessage = (e: MessageEvent) => {
+    val m = e.data.asInstanceOf[Message]
+    if (m._1 == ServerStarted) {
+      preInit.foreach(worker.postMessage(_))
+      preInit = null
+    } else
+      promises(m._1).complete(Success(m._2))
+  }
+
+  def send(cmd: WebWorkerCmd): Future[String] = {
+    val id = promises.length
+    val p  = Promise[String]()
+    val m  = Message(id, cmd.id)
+    promises.push(p)
+    if (preInit eq null)
+      worker.postMessage(m)
+    else
+      preInit.push(m)
+    p.future
+  }
+}
+
+object Client {
+
+  def workerUrl: String =
+    "file://" + BuildInfo.wwJsPath
+
+  lazy val global =
+    new Client(new Worker(workerUrl))
+}
diff --git a/tests-webworker/src/main/scala/org/scalajs/dom/tests/webworker/Protocol.scala b/tests-webworker/src/main/scala/org/scalajs/dom/tests/webworker/Protocol.scala
new file mode 100644
index 000000000..6f6829468
--- /dev/null
+++ b/tests-webworker/src/main/scala/org/scalajs/dom/tests/webworker/Protocol.scala
@@ -0,0 +1,14 @@
+package org.scalajs.dom.tests.webworker
+
+import scala.scalajs.js
+
+object Protocol {
+
+  type MsgId   = Int
+  type Message = js.Tuple2[MsgId, String]
+
+  def Message(id: MsgId, data: String): Message =
+    js.Tuple2(id, data)
+
+  final val ServerStarted: MsgId = -1
+}
diff --git a/tests-webworker/src/main/scala/org/scalajs/dom/tests/webworker/Server.scala b/tests-webworker/src/main/scala/org/scalajs/dom/tests/webworker/Server.scala
new file mode 100644
index 000000000..ba460e84e
--- /dev/null
+++ b/tests-webworker/src/main/scala/org/scalajs/dom/tests/webworker/Server.scala
@@ -0,0 +1,24 @@
+package org.scalajs.dom.tests.webworker
+
+import org.scalajs.dom.raw.MessageEvent
+import org.scalajs.dom.webworkers._
+
+object Server extends ServerResponses {
+  import Protocol._
+
+  def main(args: Array[String]): Unit = {
+    val ww = DedicatedWorkerGlobalScope.self
+
+    ww.onmessage = (e: MessageEvent) => {
+      val msgIn  = e.data.asInstanceOf[Message]
+      val id     = msgIn._1
+      val cmdId  = msgIn._2
+      val cmd    = WebWorkerCmd.byId(cmdId)
+      val output = respond(cmd)
+      val msgOut = Message(id, output)
+      ww.postMessage(msgOut)
+    }
+
+    ww.postMessage(Message(ServerStarted, ""))
+  }
+}
diff --git a/tests-webworker/src/main/scala/org/scalajs/dom/tests/webworker/WebWorkerTests.scala b/tests-webworker/src/main/scala/org/scalajs/dom/tests/webworker/WebWorkerTests.scala
new file mode 100644
index 000000000..cc40a8bd3
--- /dev/null
+++ b/tests-webworker/src/main/scala/org/scalajs/dom/tests/webworker/WebWorkerTests.scala
@@ -0,0 +1,66 @@
+package org.scalajs.dom.tests.webworker
+
+import org.junit.Assert._
+import org.junit.Test
+import org.scalajs.dom.tests.shared.AsyncTesting._
+
+// =====================================================================================================================
+sealed abstract class WebWorkerCmd {
+  def id = toString
+}
+
+object WebWorkerCmd {
+
+  case object SayHello    extends WebWorkerCmd
+  case object TestConsole extends WebWorkerCmd
+  case object TestIdb     extends WebWorkerCmd
+
+  def byId(id: String): WebWorkerCmd =
+    id match {
+      case "SayHello"    => SayHello
+      case "TestConsole" => TestConsole
+      case "TestIdb"     => TestIdb
+    }
+}
+
+import WebWorkerCmd._
+
+// =====================================================================================================================
+trait WebWorkerTests {
+  import Client.{global => client}
+
+  final protected def webWorkerTest(test: (WebWorkerCmd, String)) = async {
+    client.send(test._1).assertEquals(test._2)
+  }
+
+  @Test final def WebWorkerHelloTest() =
+    webWorkerTest(SayHello -> "hello")
+
+  @Test final def WebWorkerConsoleTest() =
+    webWorkerTest(TestConsole -> "ok")
+
+  @Test final def WebWorkerIdbTest() =
+    webWorkerTest(TestIdb -> "ok")
+}
+
+// =====================================================================================================================
+trait ServerResponses {
+  import org.scalajs.dom._
+  import org.scalajs.dom.tests.shared.SharedTests._
+  import org.scalajs.dom.webworkers.DedicatedWorkerGlobalScope.self
+
+  final val respond: WebWorkerCmd => String = {
+
+    case SayHello =>
+      "hello"
+
+    case TestConsole =>
+      console.log("WW console.log test")
+      "ok"
+
+    case TestIdb =>
+      assertTrue(self.indexedDB.isDefined)
+      testIdb(self.indexedDB.get)
+      "ok"
+  }
+}