diff --git a/.config/mill-version b/.config/mill-version
index 02840ebc763..2f2204c2bcb 100644
--- a/.config/mill-version
+++ b/.config/mill-version
@@ -1 +1 @@
-0.12.0-RC2-38-029986
\ No newline at end of file
+0.12.0-RC2-65-26cbc8
diff --git a/.github/workflows/run-mill-action.yml b/.github/workflows/run-mill-action.yml
index 0cfc4435929..cbf949255a6 100644
--- a/.github/workflows/run-mill-action.yml
+++ b/.github/workflows/run-mill-action.yml
@@ -87,4 +87,4 @@ jobs:
           path: .
           name: ${{ inputs.os }}-artifact
           include-hidden-files: true
-        if: ${{ inputs.populate_cache }}
\ No newline at end of file
+        if: ${{ inputs.populate_cache }}
diff --git a/.github/workflows/run-tests.yml b/.github/workflows/run-tests.yml
index 70eeb6f0031..7ca644d904b 100644
--- a/.github/workflows/run-tests.yml
+++ b/.github/workflows/run-tests.yml
@@ -11,8 +11,6 @@ name: Run Tests
 
 on:
   push:
-    branches:
-      - main
   pull_request:
   workflow_dispatch:
 
diff --git a/contrib/buildinfo/test/src/mill/contrib/buildinfo/BuildInfoTests.scala b/contrib/buildinfo/test/src/mill/contrib/buildinfo/BuildInfoTests.scala
index d82dfb3903c..4af8f1b5189 100644
--- a/contrib/buildinfo/test/src/mill/contrib/buildinfo/BuildInfoTests.scala
+++ b/contrib/buildinfo/test/src/mill/contrib/buildinfo/BuildInfoTests.scala
@@ -86,7 +86,7 @@ object BuildInfoTests extends TestSuite {
     )
   }
 
-  val testModuleSourcesPath: Path = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "buildinfo"
+  val testModuleSourcesPath: Path = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "buildinfo"
 
   def buildInfoSourcePath(eval: UnitTester) =
     eval.outPath / "buildInfoSources.dest/foo/BuildInfo.scala"
diff --git a/contrib/checkstyle/test/src/mill/contrib/checkstyle/CheckstyleModuleTest.scala b/contrib/checkstyle/test/src/mill/contrib/checkstyle/CheckstyleModuleTest.scala
index d93c7e17c52..dd6d6978fe7 100644
--- a/contrib/checkstyle/test/src/mill/contrib/checkstyle/CheckstyleModuleTest.scala
+++ b/contrib/checkstyle/test/src/mill/contrib/checkstyle/CheckstyleModuleTest.scala
@@ -10,7 +10,7 @@ object CheckstyleModuleTest extends TestSuite {
 
   def tests: Tests = Tests {
 
-    val resources: os.Path = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER"))
+    val resources: os.Path = os.Path(sys.env("MILL_TEST_RESOURCE_DIR"))
 
     // violations (for version 10.18.1) in "non-compatible" module
     val violations: Seq[String] =
diff --git a/contrib/checkstyle/test/src/mill/contrib/checkstyle/CheckstyleXsltModuleTest.scala b/contrib/checkstyle/test/src/mill/contrib/checkstyle/CheckstyleXsltModuleTest.scala
index f1a7e88d2b7..9be0a628ef9 100644
--- a/contrib/checkstyle/test/src/mill/contrib/checkstyle/CheckstyleXsltModuleTest.scala
+++ b/contrib/checkstyle/test/src/mill/contrib/checkstyle/CheckstyleXsltModuleTest.scala
@@ -10,7 +10,7 @@ object CheckstyleXsltModuleTest extends TestSuite {
 
   def tests: Tests = Tests {
 
-    val resources: os.Path = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER"))
+    val resources: os.Path = os.Path(sys.env("MILL_TEST_RESOURCE_DIR"))
 
     test("checkstyle generates XSLT output reports") {
 
diff --git a/contrib/docker/test/src/mill/contrib/docker/DockerModuleTest.scala b/contrib/docker/test/src/mill/contrib/docker/DockerModuleTest.scala
index 443c0b625f1..b74b545f628 100644
--- a/contrib/docker/test/src/mill/contrib/docker/DockerModuleTest.scala
+++ b/contrib/docker/test/src/mill/contrib/docker/DockerModuleTest.scala
@@ -45,7 +45,7 @@ object DockerModuleTest extends TestSuite {
 
   val testArtifactName = "mill-docker-contrib-test"
 
-  val testModuleSourcesPath: Path = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "docker"
+  val testModuleSourcesPath: Path = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "docker"
 
   val multineRegex = "\\R+".r
 
diff --git a/contrib/errorprone/test/src/mill/contrib/errorprone/ErrorProneTests.scala b/contrib/errorprone/test/src/mill/contrib/errorprone/ErrorProneTests.scala
index e40b745ea6f..c0b6bcd4bcd 100644
--- a/contrib/errorprone/test/src/mill/contrib/errorprone/ErrorProneTests.scala
+++ b/contrib/errorprone/test/src/mill/contrib/errorprone/ErrorProneTests.scala
@@ -16,7 +16,7 @@ object ErrorProneTests extends TestSuite {
     ))
   }
 
-  val testModuleSourcesPath: Path = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "simple"
+  val testModuleSourcesPath: Path = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "simple"
 
   def tests = Tests {
     test("reference") {
diff --git a/contrib/flyway/test/src/mill/contrib/flyway/BuildTest.scala b/contrib/flyway/test/src/mill/contrib/flyway/BuildTest.scala
index 1aecaa53ca9..247fe934437 100644
--- a/contrib/flyway/test/src/mill/contrib/flyway/BuildTest.scala
+++ b/contrib/flyway/test/src/mill/contrib/flyway/BuildTest.scala
@@ -10,7 +10,7 @@ object BuildTest extends TestSuite {
   object Build extends TestBaseModule {
     object build extends FlywayModule {
 
-      val resourceFolder = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER"))
+      val resourceFolder = os.Path(sys.env("MILL_TEST_RESOURCE_DIR"))
       override def resources = Task.Sources(resourceFolder)
 
       def h2 = ivy"com.h2database:h2:2.1.214"
diff --git a/contrib/jmh/test/src/mill/contrib/jmh/JmhModuleTest.scala b/contrib/jmh/test/src/mill/contrib/jmh/JmhModuleTest.scala
index 64520975b98..b5f526d9e8a 100644
--- a/contrib/jmh/test/src/mill/contrib/jmh/JmhModuleTest.scala
+++ b/contrib/jmh/test/src/mill/contrib/jmh/JmhModuleTest.scala
@@ -16,7 +16,7 @@ object JmhModuleTest extends TestSuite {
     override def scalaVersion = sys.props.getOrElse("TEST_SCALA_2_13_VERSION", ???)
     override def jmhCoreVersion = "1.35"
   }
-  val testModuleSourcesPath: Path = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "jmh"
+  val testModuleSourcesPath: Path = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "jmh"
 
   def tests = Tests {
     test("jmh") {
diff --git a/contrib/playlib/test/src/mill/playlib/PlayModuleTests.scala b/contrib/playlib/test/src/mill/playlib/PlayModuleTests.scala
index 6dfb9c79c30..afd219fcd7c 100644
--- a/contrib/playlib/test/src/mill/playlib/PlayModuleTests.scala
+++ b/contrib/playlib/test/src/mill/playlib/PlayModuleTests.scala
@@ -16,7 +16,7 @@ object PlayModuleTests extends TestSuite with PlayTestSuite {
       override def ivyDeps = Task { super.ivyDeps() ++ Agg(ws()) }
     }
   }
-  val resourcePath: os.Path = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "playmulti"
+  val resourcePath: os.Path = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "playmulti"
 
   def tests: Tests = Tests {
     test("layout") {
diff --git a/contrib/playlib/test/src/mill/playlib/PlaySingleApiModuleTests.scala b/contrib/playlib/test/src/mill/playlib/PlaySingleApiModuleTests.scala
index f6b0f67dd79..dd90a34bcd1 100644
--- a/contrib/playlib/test/src/mill/playlib/PlaySingleApiModuleTests.scala
+++ b/contrib/playlib/test/src/mill/playlib/PlaySingleApiModuleTests.scala
@@ -13,7 +13,7 @@ object PlaySingleApiModuleTests extends TestSuite with PlayTestSuite {
     object test extends PlayTests
   }
 
-  val resourcePath: os.Path = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "playsingleapi"
+  val resourcePath: os.Path = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "playsingleapi"
 
   def tests: Tests = Tests {
     test("playVersion") {
diff --git a/contrib/playlib/test/src/mill/playlib/PlaySingleModuleTests.scala b/contrib/playlib/test/src/mill/playlib/PlaySingleModuleTests.scala
index 17de9b80481..698fc0c98d3 100644
--- a/contrib/playlib/test/src/mill/playlib/PlaySingleModuleTests.scala
+++ b/contrib/playlib/test/src/mill/playlib/PlaySingleModuleTests.scala
@@ -13,7 +13,7 @@ object PlaySingleModuleTests extends TestSuite with PlayTestSuite {
     object test extends PlayTests
   }
 
-  val resourcePath: os.Path = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "playsingle"
+  val resourcePath: os.Path = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "playsingle"
 
   def tests: Tests = Tests {
     test("layout") {
diff --git a/contrib/playlib/test/src/mill/playlib/RouterModuleTests.scala b/contrib/playlib/test/src/mill/playlib/RouterModuleTests.scala
index 9431fd47312..718ddf27670 100644
--- a/contrib/playlib/test/src/mill/playlib/RouterModuleTests.scala
+++ b/contrib/playlib/test/src/mill/playlib/RouterModuleTests.scala
@@ -22,7 +22,7 @@ object RouterModuleTests extends TestSuite with PlayTestSuite {
 
   }
 
-  val resourceFolder = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER"))
+  val resourceFolder = os.Path(sys.env("MILL_TEST_RESOURCE_DIR"))
   val resourcePath: os.Path = resourceFolder / "hello-world"
   val invalidResourcePath: os.Path = resourceFolder / "invalid"
   val invalidSubResourcePath: os.Path = resourceFolder / "invalidsub"
diff --git a/contrib/proguard/test/src/mill/contrib/proguard/ProguardTests.scala b/contrib/proguard/test/src/mill/contrib/proguard/ProguardTests.scala
index 601a48fff56..d563315bc1d 100644
--- a/contrib/proguard/test/src/mill/contrib/proguard/ProguardTests.scala
+++ b/contrib/proguard/test/src/mill/contrib/proguard/ProguardTests.scala
@@ -24,7 +24,7 @@ object ProguardTests extends TestSuite {
 
   }
 
-  val testModuleSourcesPath: Path = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "proguard"
+  val testModuleSourcesPath: Path = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "proguard"
 
   def tests: Tests = Tests {
     test("Proguard module") {
diff --git a/contrib/scalapblib/test/src/mill/contrib/scalapblib/TutorialTests.scala b/contrib/scalapblib/test/src/mill/contrib/scalapblib/TutorialTests.scala
index 24c06386b70..32455fdd5fd 100644
--- a/contrib/scalapblib/test/src/mill/contrib/scalapblib/TutorialTests.scala
+++ b/contrib/scalapblib/test/src/mill/contrib/scalapblib/TutorialTests.scala
@@ -55,7 +55,7 @@ object TutorialTests extends TestSuite {
     }
   }
 
-  val resourcePath: os.Path = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER"))
+  val resourcePath: os.Path = os.Path(sys.env("MILL_TEST_RESOURCE_DIR"))
 
   def protobufOutPath(eval: UnitTester): os.Path =
     eval.outPath / "core/compileScalaPB.dest/com/example/tutorial"
diff --git a/contrib/scoverage/test/src/mill/contrib/scoverage/HelloWorldTests.scala b/contrib/scoverage/test/src/mill/contrib/scoverage/HelloWorldTests.scala
index f880e60b5cd..f2bd5744263 100644
--- a/contrib/scoverage/test/src/mill/contrib/scoverage/HelloWorldTests.scala
+++ b/contrib/scoverage/test/src/mill/contrib/scoverage/HelloWorldTests.scala
@@ -21,7 +21,7 @@ trait HelloWorldTests extends utest.TestSuite {
   def isScala3: Boolean = testScalaVersion.startsWith("3.")
   def isScov3: Boolean = testScoverageVersion.startsWith("2.")
 
-  val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "hello-world"
+  val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "hello-world"
   val sbtResourcePath = resourcePath / os.up / "hello-world-sbt"
   val unmanagedFile = resourcePath / "unmanaged.xml"
 
diff --git a/contrib/testng/test/src/mill/testng/TestNGTests.scala b/contrib/testng/test/src/mill/testng/TestNGTests.scala
index 3ba48a07da8..a512a10da67 100644
--- a/contrib/testng/test/src/mill/testng/TestNGTests.scala
+++ b/contrib/testng/test/src/mill/testng/TestNGTests.scala
@@ -37,7 +37,7 @@ object TestNGTests extends TestSuite {
 
   }
 
-  val resourcePath: os.Path = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "demo"
+  val resourcePath: os.Path = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "demo"
 
   def tests: Tests = Tests {
     test("TestNG") {
diff --git a/contrib/twirllib/test/src/mill/twirllib/HelloWorldTests.scala b/contrib/twirllib/test/src/mill/twirllib/HelloWorldTests.scala
index ef01ce49f2d..a8094cc725b 100644
--- a/contrib/twirllib/test/src/mill/twirllib/HelloWorldTests.scala
+++ b/contrib/twirllib/test/src/mill/twirllib/HelloWorldTests.scala
@@ -31,7 +31,7 @@ trait HelloWorldTests extends TestSuite {
 
   }
 
-  def resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER"))
+  def resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR"))
   def compileClassfiles: Seq[os.RelPath] = Seq[os.RelPath](
     os.rel / "html/hello.template.scala",
     os.rel / "html/wrapper.template.scala",
diff --git a/example/extending/plugins/7-writing-mill-plugins/myplugin/test/src/mill/testkit/ExampleTests.scala b/example/extending/plugins/7-writing-mill-plugins/myplugin/test/src/mill/testkit/ExampleTests.scala
index c5e7ed8dec9..e878abdc9e8 100644
--- a/example/extending/plugins/7-writing-mill-plugins/myplugin/test/src/mill/testkit/ExampleTests.scala
+++ b/example/extending/plugins/7-writing-mill-plugins/myplugin/test/src/mill/testkit/ExampleTests.scala
@@ -6,7 +6,7 @@ object ExampleTests extends TestSuite {
 
   def tests: Tests = Tests {
     test("example") {
-      val resourceFolder = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER"))
+      val resourceFolder = os.Path(sys.env("MILL_TEST_RESOURCE_DIR"))
       ExampleTester.run(
         clientServerMode = true,
         workspaceSourcePath = resourceFolder / "example-test-project",
diff --git a/example/extending/plugins/7-writing-mill-plugins/myplugin/test/src/mill/testkit/IntegrationTests.scala b/example/extending/plugins/7-writing-mill-plugins/myplugin/test/src/mill/testkit/IntegrationTests.scala
index 66c6444ab47..d957f1a1e87 100644
--- a/example/extending/plugins/7-writing-mill-plugins/myplugin/test/src/mill/testkit/IntegrationTests.scala
+++ b/example/extending/plugins/7-writing-mill-plugins/myplugin/test/src/mill/testkit/IntegrationTests.scala
@@ -10,7 +10,7 @@ object IntegrationTests extends TestSuite {
 
     test("integration") {
       pprint.log(sys.env("MILL_EXECUTABLE_PATH"))
-      val resourceFolder = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER"))
+      val resourceFolder = os.Path(sys.env("MILL_TEST_RESOURCE_DIR"))
       val tester = new IntegrationTester(
         clientServerMode = true,
         workspaceSourcePath = resourceFolder / "integration-test-project",
diff --git a/example/extending/plugins/7-writing-mill-plugins/myplugin/test/src/mill/testkit/UnitTests.scala b/example/extending/plugins/7-writing-mill-plugins/myplugin/test/src/mill/testkit/UnitTests.scala
index 8c122f9802b..44e5ab6045e 100644
--- a/example/extending/plugins/7-writing-mill-plugins/myplugin/test/src/mill/testkit/UnitTests.scala
+++ b/example/extending/plugins/7-writing-mill-plugins/myplugin/test/src/mill/testkit/UnitTests.scala
@@ -10,7 +10,7 @@ object UnitTests extends TestSuite {
         def lineCountResourceFileName = "line-count.txt"
       }
 
-      val resourceFolder = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER"))
+      val resourceFolder = os.Path(sys.env("MILL_TEST_RESOURCE_DIR"))
       UnitTester(build, resourceFolder / "unit-test-project").scoped { eval =>
 
         // Evaluating tasks by direct reference
diff --git a/example/javalib/module/7-resources/build.mill b/example/javalib/module/7-resources/build.mill
index f72a8cd072d..fc3870c5c9c 100644
--- a/example/javalib/module/7-resources/build.mill
+++ b/example/javalib/module/7-resources/build.mill
@@ -7,7 +7,7 @@ object foo extends JavaModule {
     def otherFiles = Task.Source(millSourcePath / "other-files")
 
     def forkEnv = super.forkEnv() ++ Map(
-      "OTHER_FILES_FOLDER" -> otherFiles().path.toString
+      "OTHER_FILES_DIR" -> otherFiles().path.toString
     )
   }
 }
diff --git a/example/javalib/module/7-resources/foo/test/src/FooTests.java b/example/javalib/module/7-resources/foo/test/src/FooTests.java
index c1330965dd3..fcf3f5773eb 100644
--- a/example/javalib/module/7-resources/foo/test/src/FooTests.java
+++ b/example/javalib/module/7-resources/foo/test/src/FooTests.java
@@ -26,14 +26,14 @@ public void simple() throws IOException {
     }
     assertEquals("Test Hello World Resource File A", testClasspathResourceText);
 
-    // Use `MILL_TEST_RESOURCE_FOLDER` to read `test-file-b.txt` from filesystem
-    Path testFileResourceDir = Paths.get(System.getenv("MILL_TEST_RESOURCE_FOLDER"));
+    // Use `MILL_TEST_RESOURCE_DIR` to read `test-file-b.txt` from filesystem
+    Path testFileResourceDir = Paths.get(System.getenv("MILL_TEST_RESOURCE_DIR"));
     String testFileResourceText = Files.readString(
         testFileResourceDir.resolve("test-file-b.txt")
     );
     assertEquals("Test Hello World Resource File B", testFileResourceText);
 
-    // Use `MILL_TEST_RESOURCE_FOLDER` to list files available in resource folder
+    // Use `MILL_TEST_RESOURCE_DIR` to list files available in resource folder
     List<Path> actualFiles = new ArrayList<>(Files.list(testFileResourceDir).toList());
     actualFiles.sort(Path::compareTo);
     List<Path> expectedFiles = List.of(
@@ -42,10 +42,10 @@ public void simple() throws IOException {
     );
     assertEquals(expectedFiles, actualFiles);
 
-    // Use the `OTHER_FILES_FOLDER` configured in your build to access the
+    // Use the `OTHER_FILES_DIR` configured in your build to access the
     // files in `foo/test/other-files/`.
     String otherFileText = Files.readString(
-        Paths.get(System.getenv("OTHER_FILES_FOLDER"), "other-file.txt")
+        Paths.get(System.getenv("OTHER_FILES_DIR"), "other-file.txt")
     );
     assertEquals("Other Hello World File", otherFileText);
   }
diff --git a/example/kotlinlib/module/7-resources/build.mill b/example/kotlinlib/module/7-resources/build.mill
index 59761027800..2dc39b21a1a 100644
--- a/example/kotlinlib/module/7-resources/build.mill
+++ b/example/kotlinlib/module/7-resources/build.mill
@@ -10,7 +10,7 @@ object foo extends KotlinModule {
     def otherFiles = T.source(millSourcePath / "other-files")
 
     def forkEnv = super.forkEnv() ++ Map(
-      "OTHER_FILES_FOLDER" -> otherFiles().path.toString
+      "OTHER_FILES_DIR" -> otherFiles().path.toString
     )
 
     def ivyDeps = super.ivyDeps() ++ Agg(
diff --git a/example/kotlinlib/module/7-resources/foo/test/src/FooTests.kt b/example/kotlinlib/module/7-resources/foo/test/src/FooTests.kt
index e6b5edab372..1b0297a7b65 100644
--- a/example/kotlinlib/module/7-resources/foo/test/src/FooTests.kt
+++ b/example/kotlinlib/module/7-resources/foo/test/src/FooTests.kt
@@ -24,14 +24,14 @@ class FooTests : FunSpec({
         }
         testClasspathResourceText shouldBe "Test Hello World Resource File A"
 
-        // Use `MILL_TEST_RESOURCE_FOLDER` to read `test-file-b.txt` from filesystem
-        val testFileResourceDir = Paths.get(System.getenv("MILL_TEST_RESOURCE_FOLDER"))
+        // Use `MILL_TEST_RESOURCE_DIR` to read `test-file-b.txt` from filesystem
+        val testFileResourceDir = Paths.get(System.getenv("MILL_TEST_RESOURCE_DIR"))
         val testFileResourceText = Files.readString(
             testFileResourceDir.resolve("test-file-b.txt")
         )
         testFileResourceText shouldBe "Test Hello World Resource File B"
 
-        // Use `MILL_TEST_RESOURCE_FOLDER` to list files available in resource folder
+        // Use `MILL_TEST_RESOURCE_DIR` to list files available in resource folder
         val actualFiles = Files.list(testFileResourceDir).toList().sorted()
         val expectedFiles = listOf(
             testFileResourceDir.resolve("test-file-a.txt"),
@@ -39,10 +39,10 @@ class FooTests : FunSpec({
         )
         actualFiles shouldBe expectedFiles
 
-        // Use the `OTHER_FILES_FOLDER` configured in your build to access the
+        // Use the `OTHER_FILES_DIR` configured in your build to access the
         // files in `foo/test/other-files/`.
         val otherFileText = Files.readString(
-            Paths.get(System.getenv("OTHER_FILES_FOLDER"), "other-file.txt")
+            Paths.get(System.getenv("OTHER_FILES_DIR"), "other-file.txt")
         )
         otherFileText shouldBe "Other Hello World File"
     }
diff --git a/example/scalalib/module/7-resources/build.mill b/example/scalalib/module/7-resources/build.mill
index b7facb8ca98..147ca6c0d91 100644
--- a/example/scalalib/module/7-resources/build.mill
+++ b/example/scalalib/module/7-resources/build.mill
@@ -15,7 +15,7 @@ object foo extends ScalaModule {
     def otherFiles = Task.Source(millSourcePath / "other-files")
 
     def forkEnv = super.forkEnv() ++ Map(
-      "OTHER_FILES_FOLDER" -> otherFiles().path.toString
+      "OTHER_FILES_DIR" -> otherFiles().path.toString
     )
   }
 }
@@ -33,17 +33,17 @@ object foo extends ScalaModule {
 // This section discusses how tests can depend on resources locally on disk.
 // Mill provides two ways to do this: via the JVM classpath resources, and via
 // the resource folder which is made available as the environment variable
-// `MILL_TEST_RESOURCE_FOLDER`;
+// `MILL_TEST_RESOURCE_DIR`;
 //
 // * The *classpath resources* are useful when you want to fetch individual files,
 //   and are bundled with the application by the `.assembly` step when constructing
 //   an assembly jar for deployment. But they do not allow you to list folders
 //   or perform other filesystem operations.
 //
-// * The *resource folder*, available via `MILL_TEST_RESOURCE_FOLDER`, gives you
+// * The *resource folder*, available via `MILL_TEST_RESOURCE_DIR`, gives you
 //   access to the folder path of the resources on disk. This is useful in allowing
 //   you to list and otherwise manipulate the filesystem, which you cannot do with
-//   *classpath resources*. However, the `MILL_TEST_RESOURCE_FOLDER` only exists
+//   *classpath resources*. However, the `MILL_TEST_RESOURCE_DIR` only exists
 //   when running tests using Mill, and is not available when executing applications
 //   packaged for deployment via `.assembly`
 //
diff --git a/example/scalalib/module/7-resources/foo/test/src/FooTests.scala b/example/scalalib/module/7-resources/foo/test/src/FooTests.scala
index 81fcf07b561..ab39b603263 100644
--- a/example/scalalib/module/7-resources/foo/test/src/FooTests.scala
+++ b/example/scalalib/module/7-resources/foo/test/src/FooTests.scala
@@ -11,20 +11,20 @@ object FooTests extends TestSuite {
       val testClasspathResourceText = os.read(os.resource / "test-file-a.txt")
       assert(testClasspathResourceText == "Test Hello World Resource File A")
 
-      // Use `MILL_TEST_RESOURCE_FOLDER` to read `test-file-b.txt` from filesystem
-      val testFileResourceDir = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER"))
+      // Use `MILL_TEST_RESOURCE_DIR` to read `test-file-b.txt` from filesystem
+      val testFileResourceDir = os.Path(sys.env("MILL_TEST_RESOURCE_DIR"))
       val testFileResourceText = os.read(testFileResourceDir / "test-file-b.txt")
       assert(testFileResourceText == "Test Hello World Resource File B")
 
-      // Use `MILL_TEST_RESOURCE_FOLDER` to list files available in resource folder
+      // Use `MILL_TEST_RESOURCE_DIR` to list files available in resource folder
       assert(
         os.list(testFileResourceDir).sorted ==
         Seq(testFileResourceDir / "test-file-a.txt", testFileResourceDir / "test-file-b.txt")
       )
 
-      // Use the `OTHER_FILES_FOLDER` configured in your build to access the
+      // Use the `OTHER_FILES_DIR` configured in your build to access the
       // files in `foo/test/other-files/`.
-      val otherFileText = os.read(os.Path(sys.env("OTHER_FILES_FOLDER")) / "other-file.txt")
+      val otherFileText = os.read(os.Path(sys.env("OTHER_FILES_DIR")) / "other-file.txt")
       assert(otherFileText == "Other Hello World File")
     }
   }
diff --git a/example/scalalib/testing/1-test-suite/build.mill b/example/scalalib/testing/1-test-suite/build.mill
index f5ac8acc407..aad7c2f0782 100644
--- a/example/scalalib/testing/1-test-suite/build.mill
+++ b/example/scalalib/testing/1-test-suite/build.mill
@@ -127,7 +127,7 @@ object bar extends ScalaModule {
 //
 // *Note that Mill runs tests with the working directory set to an empty `sandbox/` folder by default*.
 // Tests can access files from their resource directory via the environment variable
-// `MILL_TEST_RESOURCE_FOLDER` which provides the path to the resource folder, and additional
+// `MILL_TEST_RESOURCE_DIR` which provides the path to the resource folder, and additional
 // paths can be provided to test via `forkEnv`. See
 // xref:javalib/module-config.adoc#_classpath_and_filesystem_resources[Classpath and Filesystem Resources]
 // for more details.
diff --git a/kotlinlib/test/src/mill/kotlinlib/HelloWorldTests.scala b/kotlinlib/test/src/mill/kotlinlib/HelloWorldTests.scala
index 0ef9fd0c9e2..58592b560ef 100644
--- a/kotlinlib/test/src/mill/kotlinlib/HelloWorldTests.scala
+++ b/kotlinlib/test/src/mill/kotlinlib/HelloWorldTests.scala
@@ -28,7 +28,7 @@ object HelloWorldTests extends TestSuite {
     object main extends Cross[MainCross](kotlinVersions)
   }
 
-  val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "hello-world-kotlin"
+  val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "hello-world-kotlin"
 
   def testEval() = UnitTester(HelloWorldKotlin, resourcePath)
   def tests: Tests = Tests {
diff --git a/kotlinlib/test/src/mill/kotlinlib/MixedHelloWorldTests.scala b/kotlinlib/test/src/mill/kotlinlib/MixedHelloWorldTests.scala
index ebf96e7e899..73d68902b3e 100644
--- a/kotlinlib/test/src/mill/kotlinlib/MixedHelloWorldTests.scala
+++ b/kotlinlib/test/src/mill/kotlinlib/MixedHelloWorldTests.scala
@@ -29,7 +29,7 @@ object MixedHelloWorldTests extends TestSuite {
   }
 
   val resourcePath =
-    os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "mixed-code-hello-world-kotlin"
+    os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "mixed-code-hello-world-kotlin"
 
   def testEval() = UnitTester(MixedHelloWorldKotlin, resourcePath)
   def tests: Tests = Tests {
diff --git a/kotlinlib/test/src/mill/kotlinlib/contrib/kover/KoverModuleTests.scala b/kotlinlib/test/src/mill/kotlinlib/contrib/kover/KoverModuleTests.scala
index 57570956069..77b01f19996 100644
--- a/kotlinlib/test/src/mill/kotlinlib/contrib/kover/KoverModuleTests.scala
+++ b/kotlinlib/test/src/mill/kotlinlib/contrib/kover/KoverModuleTests.scala
@@ -13,7 +13,7 @@ object KoverModuleTests extends TestSuite {
 
   val kotlinVersion = "1.9.24"
 
-  val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "contrib" / "kover"
+  val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "contrib" / "kover"
 
   object module extends TestBaseModule {
 
diff --git a/kotlinlib/test/src/mill/kotlinlib/contrib/ktfmt/KtfmtModuleTests.scala b/kotlinlib/test/src/mill/kotlinlib/contrib/ktfmt/KtfmtModuleTests.scala
index 178f09c1038..3b9677a4218 100644
--- a/kotlinlib/test/src/mill/kotlinlib/contrib/ktfmt/KtfmtModuleTests.scala
+++ b/kotlinlib/test/src/mill/kotlinlib/contrib/ktfmt/KtfmtModuleTests.scala
@@ -15,7 +15,7 @@ object KtfmtModuleTests extends TestSuite {
   def tests: Tests = Tests {
 
     val (before, after) = {
-      val root = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "contrib" / "ktfmt"
+      val root = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "contrib" / "ktfmt"
       (root / "before", root / "after")
     }
 
diff --git a/main/client/src/mill/main/client/EnvVars.java b/main/client/src/mill/main/client/EnvVars.java
index c11b77e9c64..b0c57253470 100644
--- a/main/client/src/mill/main/client/EnvVars.java
+++ b/main/client/src/mill/main/client/EnvVars.java
@@ -11,7 +11,7 @@ public class EnvVars {
      * in a convenient fashion. If multiple resource folders are provided on the classpath,
      * they are provided as a comma-separated list
      */
-    public static final String MILL_TEST_RESOURCE_FOLDER = "MILL_TEST_RESOURCE_FOLDER";
+    public static final String MILL_TEST_RESOURCE_DIR = "MILL_TEST_RESOURCE_DIR";
 
 
     /**
diff --git a/main/eval/test/src/mill/eval/JavaCompileJarTests.scala b/main/eval/test/src/mill/eval/JavaCompileJarTests.scala
index 1e2333790cb..795529bcb41 100644
--- a/main/eval/test/src/mill/eval/JavaCompileJarTests.scala
+++ b/main/eval/test/src/mill/eval/JavaCompileJarTests.scala
@@ -18,7 +18,7 @@ object JavaCompileJarTests extends TestSuite {
     mill.api.PathRef(ctx.dest)
   }
 
-  val resourceFolder = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER"))
+  val resourceFolder = os.Path(sys.env("MILL_TEST_RESOURCE_DIR"))
   val javacSrcPath = resourceFolder / "examples/javac"
 
   val tests = Tests {
diff --git a/readme.adoc b/readme.adoc
index 0c759295161..26e9f128db6 100644
--- a/readme.adoc
+++ b/readme.adoc
@@ -483,7 +483,7 @@ prefixed with `show` and no longer need a separate `graphviz`/`dot` install on M
 
 *** Trivial upgrades that just needed to bump a version: https://github.com/com-lihaoyi/geny/pull/87 , https://github.com/com-lihaoyi/sourcecode/pull/175, https://github.com/com-lihaoyi/fansi/pull/107, https://github.com/com-lihaoyi/PPrint/pull/141, https://github.com/com-lihaoyi/mainargs/pull/159/files, https://github.com/com-lihaoyi/fastparse/pull/319, https://github.com/com-lihaoyi/scalatags/pull/284
 
-*** Less trivial upgrades, needing to make use of `MILL_TEST_RESOURCE_FOLDER` or other explicit path references to be compatible with test sandboxing: https://github.com/com-lihaoyi/requests-scala/pull/174, https://github.com/com-lihaoyi/upickle/pull/627, https://github.com/com-lihaoyi/os-lib/pull/300, https://github.com/com-lihaoyi/scalasql/pull/30
+*** Less trivial upgrades, needing to make use of `MILL_TEST_RESOURCE_DIR` or other explicit path references to be compatible with test sandboxing: https://github.com/com-lihaoyi/requests-scala/pull/174, https://github.com/com-lihaoyi/upickle/pull/627, https://github.com/com-lihaoyi/os-lib/pull/300, https://github.com/com-lihaoyi/scalasql/pull/30
 
 [#0-11-12]
 === 0.11.12 - 2024-08-20
diff --git a/scalajslib/test/src/mill/scalajslib/EsModuleRemapTests.scala b/scalajslib/test/src/mill/scalajslib/EsModuleRemapTests.scala
index ea2ef610197..025fe010679 100644
--- a/scalajslib/test/src/mill/scalajslib/EsModuleRemapTests.scala
+++ b/scalajslib/test/src/mill/scalajslib/EsModuleRemapTests.scala
@@ -41,7 +41,7 @@ object EsModuleRemapTests extends TestSuite {
     override lazy val millDiscover = Discover[this.type]
   }
 
-  val millSourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "esModuleRemap"
+  val millSourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "esModuleRemap"
 
   val tests: Tests = Tests {
     test("should remap the esmodule") {
diff --git a/scalajslib/test/src/mill/scalajslib/FullOptESModuleTests.scala b/scalajslib/test/src/mill/scalajslib/FullOptESModuleTests.scala
index 91fb3593234..9da8030876f 100644
--- a/scalajslib/test/src/mill/scalajslib/FullOptESModuleTests.scala
+++ b/scalajslib/test/src/mill/scalajslib/FullOptESModuleTests.scala
@@ -19,7 +19,7 @@ object FullOptESModuleTests extends TestSuite {
     override lazy val millDiscover = Discover[this.type]
   }
 
-  val millSourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "hello-js-world"
+  val millSourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "hello-js-world"
 
   val tests: Tests = Tests {
     test("fullOpt with ESModule moduleKind") - UnitTester(
diff --git a/scalajslib/test/src/mill/scalajslib/HelloJSWorldTests.scala b/scalajslib/test/src/mill/scalajslib/HelloJSWorldTests.scala
index e859df105f0..01ed915f9f1 100644
--- a/scalajslib/test/src/mill/scalajslib/HelloJSWorldTests.scala
+++ b/scalajslib/test/src/mill/scalajslib/HelloJSWorldTests.scala
@@ -77,7 +77,7 @@ object HelloJSWorldTests extends TestSuite {
     override lazy val millDiscover = Discover[this.type]
   }
 
-  val millSourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "hello-js-world"
+  val millSourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "hello-js-world"
 
   def tests: Tests = Tests {
     test("compile") - UnitTester(HelloJSWorld, millSourcePath).scoped { eval =>
diff --git a/scalajslib/test/src/mill/scalajslib/MultiModuleTests.scala b/scalajslib/test/src/mill/scalajslib/MultiModuleTests.scala
index 35ae03ee2b0..7df52a447d1 100644
--- a/scalajslib/test/src/mill/scalajslib/MultiModuleTests.scala
+++ b/scalajslib/test/src/mill/scalajslib/MultiModuleTests.scala
@@ -7,7 +7,7 @@ import mill.scalalib._
 import mill.testkit.{UnitTester, TestBaseModule}
 import utest._
 object MultiModuleTests extends TestSuite {
-  val sourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "multi-module"
+  val sourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "multi-module"
 
   object MultiModule extends TestBaseModule {
     trait BaseModule extends ScalaJSModule {
diff --git a/scalajslib/test/src/mill/scalajslib/NodeJSConfigTests.scala b/scalajslib/test/src/mill/scalajslib/NodeJSConfigTests.scala
index a4c1fe5db1a..730866725fa 100644
--- a/scalajslib/test/src/mill/scalajslib/NodeJSConfigTests.scala
+++ b/scalajslib/test/src/mill/scalajslib/NodeJSConfigTests.scala
@@ -54,7 +54,7 @@ object NodeJSConfigTests extends TestSuite {
     override lazy val millDiscover = Discover[this.type]
   }
 
-  val millSourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "hello-js-world"
+  val millSourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "hello-js-world"
 
   val helloWorldEvaluator = UnitTester(HelloJSWorld, millSourcePath)
 
diff --git a/scalajslib/test/src/mill/scalajslib/OutputPatternsTests.scala b/scalajslib/test/src/mill/scalajslib/OutputPatternsTests.scala
index ae181d1d2dd..34dbb7f9f6e 100644
--- a/scalajslib/test/src/mill/scalajslib/OutputPatternsTests.scala
+++ b/scalajslib/test/src/mill/scalajslib/OutputPatternsTests.scala
@@ -21,7 +21,7 @@ object OutputPatternsTests extends TestSuite {
     override lazy val millDiscover = Discover[this.type]
   }
 
-  val millSourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "hello-js-world"
+  val millSourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "hello-js-world"
 
   val evaluator = UnitTester(OutputPatternsModule, millSourcePath)
 
diff --git a/scalajslib/test/src/mill/scalajslib/SmallModulesForTests.scala b/scalajslib/test/src/mill/scalajslib/SmallModulesForTests.scala
index eb88e5408ba..25c5c7150b2 100644
--- a/scalajslib/test/src/mill/scalajslib/SmallModulesForTests.scala
+++ b/scalajslib/test/src/mill/scalajslib/SmallModulesForTests.scala
@@ -18,7 +18,7 @@ object SmallModulesForTests extends TestSuite {
     override lazy val millDiscover = Discover[this.type]
   }
 
-  val millSourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "small-modules-for"
+  val millSourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "small-modules-for"
 
   val evaluator = UnitTester(SmallModulesForModule, millSourcePath)
 
diff --git a/scalajslib/test/src/mill/scalajslib/SourceMapTests.scala b/scalajslib/test/src/mill/scalajslib/SourceMapTests.scala
index f0a128f09f5..a52ba7edaa3 100644
--- a/scalajslib/test/src/mill/scalajslib/SourceMapTests.scala
+++ b/scalajslib/test/src/mill/scalajslib/SourceMapTests.scala
@@ -18,7 +18,7 @@ object SourceMapTests extends TestSuite {
     override lazy val millDiscover = Discover[this.type]
   }
 
-  val millSourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "hello-js-world"
+  val millSourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "hello-js-world"
 
   val evaluator = UnitTester(SourceMapModule, millSourcePath)
 
diff --git a/scalajslib/test/src/mill/scalajslib/TopLevelExportsTests.scala b/scalajslib/test/src/mill/scalajslib/TopLevelExportsTests.scala
index a1c409748de..6ea7bbaf780 100644
--- a/scalajslib/test/src/mill/scalajslib/TopLevelExportsTests.scala
+++ b/scalajslib/test/src/mill/scalajslib/TopLevelExportsTests.scala
@@ -16,7 +16,7 @@ object TopLevelExportsTests extends TestSuite {
     override lazy val millDiscover = Discover[this.type]
   }
 
-  val millSourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "top-level-exports"
+  val millSourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "top-level-exports"
 
   val evaluator = UnitTester(TopLevelExportsModule, millSourcePath)
 
diff --git a/scalalib/src/mill/scalalib/TestModuleUtil.scala b/scalalib/src/mill/scalalib/TestModuleUtil.scala
index bddb0a37c55..3db401c3259 100644
--- a/scalalib/src/mill/scalalib/TestModuleUtil.scala
+++ b/scalalib/src/mill/scalalib/TestModuleUtil.scala
@@ -38,8 +38,7 @@ private[scalalib] object TestModuleUtil {
       .mkString(",")
 
     val resourceEnv = Map(
-      "MILL_TEST_RESOURCE_DIR" -> resources.map(_.path).mkString(";"),
-      EnvVars.MILL_TEST_RESOURCE_FOLDER -> resources.map(_.path).mkString(";"),
+      EnvVars.MILL_TEST_RESOURCE_DIR -> resources.map(_.path).mkString(";"),
       EnvVars.MILL_WORKSPACE_ROOT -> T.workspace.toString
     )
 
diff --git a/scalalib/test/src/mill/javalib/palantirformat/PalantirFormatModuleTest.scala b/scalalib/test/src/mill/javalib/palantirformat/PalantirFormatModuleTest.scala
index d76b078eadc..540e3b76282 100644
--- a/scalalib/test/src/mill/javalib/palantirformat/PalantirFormatModuleTest.scala
+++ b/scalalib/test/src/mill/javalib/palantirformat/PalantirFormatModuleTest.scala
@@ -11,7 +11,7 @@ object PalantirFormatModuleTest extends TestSuite {
   def tests: Tests = Tests {
 
     val (before, after) = {
-      val root = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "javalib" / "palantirformat"
+      val root = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "javalib" / "palantirformat"
       (root / "before", root / "after")
     }
 
diff --git a/scalalib/test/src/mill/scalalib/AssemblyTests.scala b/scalalib/test/src/mill/scalalib/AssemblyTests.scala
index 0cc7537801c..72af5839fda 100644
--- a/scalalib/test/src/mill/scalalib/AssemblyTests.scala
+++ b/scalalib/test/src/mill/scalalib/AssemblyTests.scala
@@ -54,7 +54,7 @@ object AssemblyTests extends TestSuite {
 
   }
 
-  val sources = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "assembly"
+  val sources = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "assembly"
 
   def runAssembly(file: os.Path, wd: os.Path, checkExe: Boolean = false): Unit = {
     println(s"File size: ${os.stat(file).size}")
diff --git a/scalalib/test/src/mill/scalalib/CoursierMirrorTests.scala b/scalalib/test/src/mill/scalalib/CoursierMirrorTests.scala
index b72c882fbd2..91000d0549e 100644
--- a/scalalib/test/src/mill/scalalib/CoursierMirrorTests.scala
+++ b/scalalib/test/src/mill/scalalib/CoursierMirrorTests.scala
@@ -8,7 +8,7 @@ import utest.framework.TestPath
 
 object CoursierMirrorTests extends TestSuite {
 
-  val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "coursier"
+  val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "coursier"
 
   object CoursierTest extends TestBaseModule {
     object core extends ScalaModule {
diff --git a/scalalib/test/src/mill/scalalib/DottyDocTests.scala b/scalalib/test/src/mill/scalalib/DottyDocTests.scala
index 8f948fd3840..53c5b9f9b9d 100644
--- a/scalalib/test/src/mill/scalalib/DottyDocTests.scala
+++ b/scalalib/test/src/mill/scalalib/DottyDocTests.scala
@@ -32,7 +32,7 @@ object DottyDocTests extends TestSuite {
     }
   }
 
-  val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "dottydoc"
+  val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "dottydoc"
 
   def tests: Tests = Tests {
     test("static") - UnitTester(StaticDocsModule, resourcePath).scoped { eval =>
diff --git a/scalalib/test/src/mill/scalalib/HelloJavaTests.scala b/scalalib/test/src/mill/scalalib/HelloJavaTests.scala
index 4faf5d28f99..7c8a0461087 100644
--- a/scalalib/test/src/mill/scalalib/HelloJavaTests.scala
+++ b/scalalib/test/src/mill/scalalib/HelloJavaTests.scala
@@ -25,7 +25,7 @@ object HelloJavaTests extends TestSuite {
       }
     }
   }
-  val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "hello-java"
+  val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "hello-java"
 
   def testEval() = UnitTester(HelloJava, resourcePath)
   def tests: Tests = Tests {
diff --git a/scalalib/test/src/mill/scalalib/HelloWorldTests.scala b/scalalib/test/src/mill/scalalib/HelloWorldTests.scala
index 32f3b352cf9..0f3ced9dc95 100644
--- a/scalalib/test/src/mill/scalalib/HelloWorldTests.scala
+++ b/scalalib/test/src/mill/scalalib/HelloWorldTests.scala
@@ -80,7 +80,7 @@ object HelloWorldTests extends TestSuite {
     }
   }
 
-  val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "hello-world"
+  val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "hello-world"
 
   def jarMainClass(jar: JarFile): Option[String] = {
     import java.util.jar.Attributes._
diff --git a/scalalib/test/src/mill/scalalib/PublishModuleTests.scala b/scalalib/test/src/mill/scalalib/PublishModuleTests.scala
index 3459b5f9577..fb04528779b 100644
--- a/scalalib/test/src/mill/scalalib/PublishModuleTests.scala
+++ b/scalalib/test/src/mill/scalalib/PublishModuleTests.scala
@@ -77,7 +77,7 @@ object PublishModuleTests extends TestSuite {
     }
   }
 
-  val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "publish"
+  val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "publish"
 
   def tests: Tests = Tests {
     test("pom") {
diff --git a/scalalib/test/src/mill/scalalib/ScalaAssemblyTests.scala b/scalalib/test/src/mill/scalalib/ScalaAssemblyTests.scala
index 4ec530e064c..75a38958b20 100644
--- a/scalalib/test/src/mill/scalalib/ScalaAssemblyTests.scala
+++ b/scalalib/test/src/mill/scalalib/ScalaAssemblyTests.scala
@@ -148,7 +148,7 @@ object ScalaAssemblyTests extends TestSuite {
           }
 
         val helloWorldMultiResourcePath =
-          os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "hello-world-multi"
+          os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "hello-world-multi"
 
         def checkAppendMulti[M <: mill.testkit.TestBaseModule](
             module: M,
@@ -268,7 +268,7 @@ object ScalaAssemblyTests extends TestSuite {
 
           test("run") - UnitTester(
             HelloWorldAkkaHttpRelocate,
-            sourceRoot = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "hello-world-deps"
+            sourceRoot = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "hello-world-deps"
           ).scoped { eval =>
             val Right(result) = eval.apply(HelloWorldAkkaHttpRelocate.core.runMain("Main"))
             assert(result.evalCount > 0)
diff --git a/scalalib/test/src/mill/scalalib/ScalaColorOutputTests.scala b/scalalib/test/src/mill/scalalib/ScalaColorOutputTests.scala
index 75362f721a9..6b9a815d464 100644
--- a/scalalib/test/src/mill/scalalib/ScalaColorOutputTests.scala
+++ b/scalalib/test/src/mill/scalalib/ScalaColorOutputTests.scala
@@ -25,7 +25,7 @@ object ScalaColorOutputTests extends TestSuite {
 
       UnitTester(
         HelloWorldColorOutput,
-        sourceRoot = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "hello-world-color-output",
+        sourceRoot = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "hello-world-color-output",
         errStream = new PrintStream(errStream, true)
       ).scoped { eval =>
         val Left(Result.Failure("Compilation failed", _)) =
diff --git a/scalalib/test/src/mill/scalalib/ScalaDoc3Tests.scala b/scalalib/test/src/mill/scalalib/ScalaDoc3Tests.scala
index ee3245e9a05..5f070076c65 100644
--- a/scalalib/test/src/mill/scalalib/ScalaDoc3Tests.scala
+++ b/scalalib/test/src/mill/scalalib/ScalaDoc3Tests.scala
@@ -32,7 +32,7 @@ object ScalaDoc3Tests extends TestSuite {
     }
   }
 
-  val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "scaladoc3"
+  val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "scaladoc3"
 
   def tests: Tests = Tests {
     test("static") - UnitTester(StaticDocsModule, resourcePath).scoped { eval =>
diff --git a/scalalib/test/src/mill/scalalib/ScalaDotty213Tests.scala b/scalalib/test/src/mill/scalalib/ScalaDotty213Tests.scala
index c12fe2ee283..8f6f2acaf95 100644
--- a/scalalib/test/src/mill/scalalib/ScalaDotty213Tests.scala
+++ b/scalalib/test/src/mill/scalalib/ScalaDotty213Tests.scala
@@ -17,7 +17,7 @@ object ScalaDotty213Tests extends TestSuite {
 
     test("dotty213") - UnitTester(
       Dotty213,
-      sourceRoot = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "dotty213"
+      sourceRoot = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "dotty213"
     ).scoped { eval =>
       val Right(result) = eval.apply(Dotty213.foo.run())
       assert(result.evalCount > 0)
diff --git a/scalalib/test/src/mill/scalalib/ScalaFlagsTests.scala b/scalalib/test/src/mill/scalalib/ScalaFlagsTests.scala
index c06893f8df3..4ba5307c001 100644
--- a/scalalib/test/src/mill/scalalib/ScalaFlagsTests.scala
+++ b/scalalib/test/src/mill/scalalib/ScalaFlagsTests.scala
@@ -21,7 +21,7 @@ object ScalaFlagsTests extends TestSuite {
       // make sure flags are passed when compiling/running
       test("runMain") - UnitTester(
         HelloWorldFlags,
-        sourceRoot = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "hello-world-flags"
+        sourceRoot = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "hello-world-flags"
       ).scoped { eval =>
         val Right(result) = eval.apply(HelloWorldFlags.core.runMain("Main"))
         assert(result.evalCount > 0)
@@ -29,7 +29,7 @@ object ScalaFlagsTests extends TestSuite {
       // make sure flags are passed during ScalaDoc generation
       test("docJar") - UnitTester(
         HelloWorldFlags,
-        sourceRoot = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "hello-world-flags"
+        sourceRoot = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "hello-world-flags"
       ).scoped { eval =>
         val Right(result) = eval.apply(HelloWorldFlags.core.docJar)
         assert(result.evalCount > 0)
diff --git a/scalalib/test/src/mill/scalalib/ScalaMacrosTests.scala b/scalalib/test/src/mill/scalalib/ScalaMacrosTests.scala
index 1f61e841710..540bdf77d0b 100644
--- a/scalalib/test/src/mill/scalalib/ScalaMacrosTests.scala
+++ b/scalalib/test/src/mill/scalalib/ScalaMacrosTests.scala
@@ -36,7 +36,7 @@ object ScalaMacrosTests extends TestSuite {
         val mod = HelloWorldMacros212
         test("runMain") - UnitTester(
           mod,
-          sourceRoot = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "hello-world-macros"
+          sourceRoot = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "hello-world-macros"
         ).scoped { eval =>
           if (Properties.isJavaAtLeast(17)) "skipped on Java 17+"
           else {
@@ -47,7 +47,7 @@ object ScalaMacrosTests extends TestSuite {
         // make sure macros are applied when compiling during scaladoc generation
         test("docJar") - UnitTester(
           mod,
-          sourceRoot = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "hello-world-macros"
+          sourceRoot = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "hello-world-macros"
         ).scoped { eval =>
           if (Properties.isJavaAtLeast(17)) "skipped on Java 17+"
           else {
@@ -61,7 +61,7 @@ object ScalaMacrosTests extends TestSuite {
         val mod = HelloWorldMacros213
         test("runMain") - UnitTester(
           mod,
-          sourceRoot = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "hello-world-macros"
+          sourceRoot = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "hello-world-macros"
         ).scoped { eval =>
           val Right(result) = eval.apply(mod.core.runMain("Main"))
           assert(result.evalCount > 0)
@@ -69,7 +69,7 @@ object ScalaMacrosTests extends TestSuite {
         // make sure macros are applied when compiling during scaladoc generation
         test("docJar") - UnitTester(
           mod,
-          sourceRoot = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "hello-world-macros"
+          sourceRoot = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "hello-world-macros"
         ).scoped { eval =>
           val Right(result) = eval.apply(mod.core.docJar)
           assert(result.evalCount > 0)
diff --git a/scalalib/test/src/mill/scalalib/ScalaRunTests.scala b/scalalib/test/src/mill/scalalib/ScalaRunTests.scala
index a7ce992e027..1122268cfcf 100644
--- a/scalalib/test/src/mill/scalalib/ScalaRunTests.scala
+++ b/scalalib/test/src/mill/scalalib/ScalaRunTests.scala
@@ -104,7 +104,7 @@ object ScalaRunTests extends TestSuite {
       }
       test("notRunWithoutMainClass") - UnitTester(
         HelloWorldWithoutMain,
-        sourceRoot = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "hello-world-no-main"
+        sourceRoot = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "hello-world-no-main"
       ).scoped { eval =>
         val Left(Result.Failure(_, None)) = eval.apply(HelloWorldWithoutMain.core.run())
       }
@@ -156,7 +156,7 @@ object ScalaRunTests extends TestSuite {
       }
       test("notRunWithoutMainClass") - UnitTester(
         HelloWorldWithoutMain,
-        sourceRoot = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "hello-world-no-main"
+        sourceRoot = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "hello-world-no-main"
       ).scoped { eval =>
         val Left(Result.Failure(_, None)) = eval.apply(HelloWorldWithoutMain.core.runLocal())
       }
diff --git a/scalalib/test/src/mill/scalalib/ScalaScalacheckTests.scala b/scalalib/test/src/mill/scalalib/ScalaScalacheckTests.scala
index bf86b1c9387..93fc75003a9 100644
--- a/scalalib/test/src/mill/scalalib/ScalaScalacheckTests.scala
+++ b/scalalib/test/src/mill/scalalib/ScalaScalacheckTests.scala
@@ -21,7 +21,7 @@ object ScalaScalacheckTests extends TestSuite {
 
     test("scalacheck") - UnitTester(
       HelloScalacheck,
-      sourceRoot = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "hello-scalacheck"
+      sourceRoot = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "hello-scalacheck"
     ).scoped { eval =>
       val Right(result) = eval.apply(HelloScalacheck.foo.test.test())
       assert(
diff --git a/scalalib/test/src/mill/scalalib/ScalaScaladocTests.scala b/scalalib/test/src/mill/scalalib/ScalaScaladocTests.scala
index 1ef99235fb1..f68c67d4e23 100644
--- a/scalalib/test/src/mill/scalalib/ScalaScaladocTests.scala
+++ b/scalalib/test/src/mill/scalalib/ScalaScaladocTests.scala
@@ -54,7 +54,7 @@ object ScalaScaladocTests extends TestSuite {
       // make sure options are passed during ScalaDoc generation
       test("docJarWithTitle") - UnitTester(
         HelloWorldDocTitle,
-        sourceRoot = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "hello-world"
+        sourceRoot = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "hello-world"
       ).scoped { eval =>
         val Right(result) = eval.apply(HelloWorldDocTitle.core.docJar)
         assert(
@@ -66,14 +66,14 @@ object ScalaScaladocTests extends TestSuite {
       }
       test("docJarWithVersion") - UnitTester(
         HelloWorldWithDocVersion,
-        sourceRoot = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "hello-world"
+        sourceRoot = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "hello-world"
       ).scoped { eval =>
         // scaladoc generation fails because of "-Xfatal-warnings" flag
         val Left(Result.Failure(_, None)) = eval.apply(HelloWorldWithDocVersion.core.docJar)
       }
       test("docJarOnlyVersion") - UnitTester(
         HelloWorldOnlyDocVersion,
-        sourceRoot = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "hello-world"
+        sourceRoot = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "hello-world"
       ).scoped { eval =>
         // `docJar` requires the `compile` task to succeed (since the addition of Scaladoc 3)
         val Left(Result.Failure(_, None)) = eval.apply(HelloWorldOnlyDocVersion.core.docJar)
diff --git a/scalalib/test/src/mill/scalalib/ScalaVersionsRangesTests.scala b/scalalib/test/src/mill/scalalib/ScalaVersionsRangesTests.scala
index feef4991855..3da405e9fad 100644
--- a/scalalib/test/src/mill/scalalib/ScalaVersionsRangesTests.scala
+++ b/scalalib/test/src/mill/scalalib/ScalaVersionsRangesTests.scala
@@ -18,7 +18,7 @@ object ScalaVersionsRangesTests extends TestSuite {
     }
   }
   val resourcePath =
-    os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "scala-versions-ranges"
+    os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "scala-versions-ranges"
 
   val tests = Tests {
     test("main with Scala 2.12- and 2.13+ specific code") - UnitTester(
diff --git a/scalalib/test/src/mill/scalalib/TestClassLoaderTests.scala b/scalalib/test/src/mill/scalalib/TestClassLoaderTests.scala
index 09365585ae8..2889b77ba14 100644
--- a/scalalib/test/src/mill/scalalib/TestClassLoaderTests.scala
+++ b/scalalib/test/src/mill/scalalib/TestClassLoaderTests.scala
@@ -20,7 +20,7 @@ object TestClassLoaderTests extends TestSuite {
     }
   }
 
-  val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "classloader-test"
+  val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "classloader-test"
 
   override def tests: Tests = Tests {
     test("com.sun classes exist in tests classpath (Java 8 only)") - UnitTester(
diff --git a/scalalib/test/src/mill/scalalib/TestRunnerTests.scala b/scalalib/test/src/mill/scalalib/TestRunnerTests.scala
index 8dd71221cc1..c85fa702b1c 100644
--- a/scalalib/test/src/mill/scalalib/TestRunnerTests.scala
+++ b/scalalib/test/src/mill/scalalib/TestRunnerTests.scala
@@ -70,7 +70,7 @@ object TestRunnerTests extends TestSuite {
     }
   }
 
-  val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "testrunner"
+  val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "testrunner"
 
   override def tests: Tests = Tests {
     test("TestRunner") - {
diff --git a/scalalib/test/src/mill/scalalib/scalafmt/ScalafmtTests.scala b/scalalib/test/src/mill/scalalib/scalafmt/ScalafmtTests.scala
index 471a02ad921..6fbb02332c9 100644
--- a/scalalib/test/src/mill/scalalib/scalafmt/ScalafmtTests.scala
+++ b/scalalib/test/src/mill/scalalib/scalafmt/ScalafmtTests.scala
@@ -27,7 +27,7 @@ object ScalafmtTests extends TestSuite {
     }
   }
 
-  val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "scalafmt"
+  val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "scalafmt"
 
   def tests: Tests = Tests {
     test("scalafmt") {
diff --git a/scalanativelib/src/mill/scalanativelib/ScalaNativeModule.scala b/scalanativelib/src/mill/scalanativelib/ScalaNativeModule.scala
index 241687aa8da..44c18789178 100644
--- a/scalanativelib/src/mill/scalanativelib/ScalaNativeModule.scala
+++ b/scalanativelib/src/mill/scalanativelib/ScalaNativeModule.scala
@@ -356,8 +356,7 @@ trait TestScalaNativeModule extends ScalaNativeModule with TestModule {
       nativeLink().toIO,
       forkEnv() ++
         Map(
-          "MILL_TEST_RESOURCE_DIR" -> resources().map(_.path).mkString(";"),
-          EnvVars.MILL_TEST_RESOURCE_FOLDER -> resources().map(_.path).mkString(";"),
+          EnvVars.MILL_TEST_RESOURCE_DIR -> resources().map(_.path).mkString(";"),
           EnvVars.MILL_WORKSPACE_ROOT -> T.workspace.toString
         ),
       toWorkerApi(logLevel()),
diff --git a/scalanativelib/test/resources/hello-native-world/build/test/src/utest/tests/MainTests.scala b/scalanativelib/test/resources/hello-native-world/build/test/src/utest/tests/MainTests.scala
index 739c1b978a0..7ddd93d8591 100644
--- a/scalanativelib/test/resources/hello-native-world/build/test/src/utest/tests/MainTests.scala
+++ b/scalanativelib/test/resources/hello-native-world/build/test/src/utest/tests/MainTests.scala
@@ -20,13 +20,13 @@ object MainTests extends TestSuite {
       }
       test("resource") {
         val expected = new java.util.ArrayList[Path]()
-        expected.add(Paths.get(sys.env("MILL_TEST_RESOURCE_FOLDER") + "/hello-resource.txt"))
+        expected.add(Paths.get(sys.env("MILL_TEST_RESOURCE_DIR") + "/hello-resource.txt"))
         val listed =
-          Files.list(Paths.get(sys.env("MILL_TEST_RESOURCE_FOLDER"))).collect(Collectors.toList())
+          Files.list(Paths.get(sys.env("MILL_TEST_RESOURCE_DIR"))).collect(Collectors.toList())
         assert(listed == expected)
         assert(
           Files.readString(
-            Paths.get(sys.env("MILL_TEST_RESOURCE_FOLDER") + "/hello-resource.txt")
+            Paths.get(sys.env("MILL_TEST_RESOURCE_DIR") + "/hello-resource.txt")
           ) ==
             "hello world resource text"
         )
diff --git a/scalanativelib/test/src/mill/scalanativelib/FeaturesTests.scala b/scalanativelib/test/src/mill/scalanativelib/FeaturesTests.scala
index c151c559662..a796c0c9542 100644
--- a/scalanativelib/test/src/mill/scalanativelib/FeaturesTests.scala
+++ b/scalanativelib/test/src/mill/scalanativelib/FeaturesTests.scala
@@ -13,7 +13,7 @@ object FeaturesTests extends TestSuite {
     override lazy val millDiscover: Discover = Discover[this.type]
   }
 
-  val millSourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "features"
+  val millSourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "features"
 
   val tests: Tests = Tests {
     test("incremental compilation works") - UnitTester(Features, millSourcePath).scoped { eval =>
diff --git a/scalanativelib/test/src/mill/scalanativelib/HelloNativeWorldTests.scala b/scalanativelib/test/src/mill/scalanativelib/HelloNativeWorldTests.scala
index 6ac688780f3..f74567df940 100644
--- a/scalanativelib/test/src/mill/scalanativelib/HelloNativeWorldTests.scala
+++ b/scalanativelib/test/src/mill/scalanativelib/HelloNativeWorldTests.scala
@@ -79,7 +79,7 @@ object HelloNativeWorldTests extends TestSuite {
     override lazy val millDiscover: Discover = Discover[this.type]
   }
 
-  val millSourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "hello-native-world"
+  val millSourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "hello-native-world"
 
   def tests: Tests = Tests {
     test("compile") {
diff --git a/testkit/src/mill/testkit/UtestExampleTestSuite.scala b/testkit/src/mill/testkit/UtestExampleTestSuite.scala
index 7863d2473e3..0a6ccb1b81a 100644
--- a/testkit/src/mill/testkit/UtestExampleTestSuite.scala
+++ b/testkit/src/mill/testkit/UtestExampleTestSuite.scala
@@ -5,7 +5,7 @@ import utest._
 import scala.concurrent.duration.DurationInt
 
 object UtestExampleTestSuite extends TestSuite {
-  val workspaceSourcePath: os.Path = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER"))
+  val workspaceSourcePath: os.Path = os.Path(sys.env("MILL_TEST_RESOURCE_DIR"))
   val clientServerMode: Boolean = sys.env("MILL_INTEGRATION_SERVER_MODE").toBoolean
 
   val millExecutable: os.Path = os.Path(System.getenv("MILL_INTEGRATION_LAUNCHER"), os.pwd)
diff --git a/testkit/src/mill/testkit/UtestIntegrationTestSuite.scala b/testkit/src/mill/testkit/UtestIntegrationTestSuite.scala
index d3c5d77a38d..6c1b5efb25b 100644
--- a/testkit/src/mill/testkit/UtestIntegrationTestSuite.scala
+++ b/testkit/src/mill/testkit/UtestIntegrationTestSuite.scala
@@ -5,7 +5,7 @@ import scala.concurrent.duration.DurationInt
 import scala.concurrent.{ExecutionContext, Future}
 
 abstract class UtestIntegrationTestSuite extends utest.TestSuite with IntegrationTestSuite {
-  protected def workspaceSourcePath: os.Path = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER"))
+  protected def workspaceSourcePath: os.Path = os.Path(sys.env("MILL_TEST_RESOURCE_DIR"))
   protected def clientServerMode: Boolean = sys.env("MILL_INTEGRATION_SERVER_MODE").toBoolean
   protected def millExecutable: os.Path =
     os.Path(System.getenv("MILL_INTEGRATION_LAUNCHER"), os.pwd)
diff --git a/testkit/test/src/mill/testkit/ExampleTesterTests.scala b/testkit/test/src/mill/testkit/ExampleTesterTests.scala
index 5d7d36072ee..53879a0a5dc 100644
--- a/testkit/test/src/mill/testkit/ExampleTesterTests.scala
+++ b/testkit/test/src/mill/testkit/ExampleTesterTests.scala
@@ -9,7 +9,7 @@ object ExampleTesterTests extends TestSuite {
       ExampleTester.run(
         clientServerMode = true,
         workspaceSourcePath =
-          os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "example-test-example-project",
+          os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "example-test-example-project",
         millExecutable = os.Path(sys.env("MILL_EXECUTABLE_PATH"))
       )
     }
diff --git a/testkit/test/src/mill/testkit/IntegrationTesterTests.scala b/testkit/test/src/mill/testkit/IntegrationTesterTests.scala
index 9172a036427..4afbd81cf26 100644
--- a/testkit/test/src/mill/testkit/IntegrationTesterTests.scala
+++ b/testkit/test/src/mill/testkit/IntegrationTesterTests.scala
@@ -5,7 +5,7 @@ import utest._
 object IntegrationTesterTests extends TestSuite with IntegrationTestSuite {
   def clientServerMode = true
   def workspaceSourcePath =
-    os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "integration-test-example-project"
+    os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "integration-test-example-project"
   def millExecutable = os.Path(sys.env("MILL_EXECUTABLE_PATH"))
   def tests: Tests = Tests {
 
diff --git a/testkit/test/src/mill/testkit/UnitTesterTests.scala b/testkit/test/src/mill/testkit/UnitTesterTests.scala
index 801c92bbe7b..96aeb9c66c5 100644
--- a/testkit/test/src/mill/testkit/UnitTesterTests.scala
+++ b/testkit/test/src/mill/testkit/UnitTesterTests.scala
@@ -5,7 +5,7 @@ import utest._
 
 object UnitTesterTests extends TestSuite {
 
-  val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_FOLDER")) / "unit-test-example-project"
+  val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "unit-test-example-project"
   def tests: Tests = Tests {
     test("simple") {
       object build extends TestBaseModule {