diff --git a/src/test/groovy/com/github/jengelman/gradle/plugins/shadow/caching/AbstractCachingSpec.groovy b/src/test/groovy/com/github/jengelman/gradle/plugins/shadow/caching/AbstractCachingSpec.groovy
index 16940a296..bd33ca03d 100644
--- a/src/test/groovy/com/github/jengelman/gradle/plugins/shadow/caching/AbstractCachingSpec.groovy
+++ b/src/test/groovy/com/github/jengelman/gradle/plugins/shadow/caching/AbstractCachingSpec.groovy
@@ -4,14 +4,15 @@ import com.github.jengelman.gradle.plugins.shadow.util.PluginSpecification
 import org.apache.commons.io.FileUtils
 import org.gradle.testkit.runner.BuildResult
 import org.gradle.testkit.runner.TaskOutcome
-import org.junit.Rule
-import org.junit.rules.TemporaryFolder
+import spock.lang.TempDir
+
+import java.nio.file.Path
 
 import static org.gradle.testkit.runner.TaskOutcome.FROM_CACHE
 import static org.gradle.testkit.runner.TaskOutcome.SUCCESS
 
 abstract class AbstractCachingSpec extends PluginSpecification {
-    @Rule TemporaryFolder alternateDir
+    @TempDir Path alternateDir
 
     @Override
     def setup() {
@@ -41,7 +42,7 @@ abstract class AbstractCachingSpec extends PluginSpecification {
         List<String> cacheArguments = [ '--build-cache' ]
         cacheArguments.addAll(arguments)
         // TODO: Use PluginSpecification.run here to reuse flags, but cache tests failed for now, need to investigate.
-        return runner.withProjectDir(alternateDir.root).withArguments(cacheArguments).build()
+        return runner.withProjectDir(alternateDir.toFile()).withArguments(cacheArguments).build()
     }
 
     private String escapedPath(File file) {
@@ -59,9 +60,9 @@ abstract class AbstractCachingSpec extends PluginSpecification {
     }
 
     void copyToAlternateDir() {
-        FileUtils.deleteDirectory(alternateDir.root)
-        FileUtils.forceMkdir(alternateDir.root)
-        FileUtils.copyDirectory(dir.root, alternateDir.root)
+        FileUtils.deleteDirectory(alternateDir.toFile())
+        FileUtils.forceMkdir(alternateDir.toFile())
+        FileUtils.copyDirectory(dir.toFile(), alternateDir.toFile())
     }
 
     void assertShadowJarIsCachedAndRelocatable() {
diff --git a/src/test/groovy/com/github/jengelman/gradle/plugins/shadow/util/PluginSpecification.groovy b/src/test/groovy/com/github/jengelman/gradle/plugins/shadow/util/PluginSpecification.groovy
index 9e5fc66f4..36b5d12c1 100644
--- a/src/test/groovy/com/github/jengelman/gradle/plugins/shadow/util/PluginSpecification.groovy
+++ b/src/test/groovy/com/github/jengelman/gradle/plugins/shadow/util/PluginSpecification.groovy
@@ -7,14 +7,16 @@ import org.gradle.testkit.runner.GradleRunner
 import org.junit.Rule
 import org.junit.rules.TemporaryFolder
 import spock.lang.Specification
+import spock.lang.TempDir
 
+import java.nio.file.Path
 import java.util.function.Function
 import java.util.jar.JarEntry
 import java.util.jar.JarFile
 
 abstract class PluginSpecification extends Specification {
 
-    @Rule TemporaryFolder dir
+    @TempDir Path dir
 
     public static final String SHADOW_VERSION = System.getProperty("shadowVersion")
 
@@ -55,7 +57,7 @@ abstract class PluginSpecification extends Specification {
 
     GradleRunner getRunner() {
         GradleRunner.create()
-                .withProjectDir(dir.root)
+                .withProjectDir(dir.toFile())
                 .forwardOutput()
                 .withPluginClasspath()
     }
@@ -104,20 +106,22 @@ abstract class PluginSpecification extends Specification {
     }
 
     File file(String path) {
-        File f = new File(dir.root, path)
+        File f = dir.resolve(path).toFile()
         if (!f.exists()) {
             f.parentFile.mkdirs()
-            return dir.newFile(path)
+            if (!f.createNewFile()) {
+                throw new IOException("a file with the name \'" + f.name + "\' already exists in the test folder.")
+            }
         }
         return f
     }
 
     File getFile(String path) {
-        new File(dir.root, path)
+        new File(dir.root.toFile(), path)
     }
 
     AppendableMavenFileRepository repo(String path = 'maven-repo') {
-        new AppendableMavenFileRepository(new TestFile(dir.root, path))
+        new AppendableMavenFileRepository(new TestFile(dir.toFile(), path))
     }
 
     void assertJarFileContentsEqual(File f, String path, String contents) {