diff --git a/build.gradle.kts b/build.gradle.kts
index bf84d0158..d28ae0509 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -48,7 +48,7 @@ val testKitImplementation: Configuration by configurations.getting
 
 val intiTest: SourceSet by sourceSets.creating
 val intiTestImplementation: Configuration by configurations.getting {
-  extendsFrom(configurations.testImplementation.get())
+  extendsFrom(testKitImplementation, configurations.testImplementation.get())
 }
 val intiTestRuntimeOnly: Configuration by configurations.getting {
   extendsFrom(configurations.testRuntimeOnly.get())
@@ -56,7 +56,7 @@ val intiTestRuntimeOnly: Configuration by configurations.getting {
 
 val funcTest: SourceSet by sourceSets.creating
 val funcTestImplementation: Configuration by configurations.getting {
-  extendsFrom(configurations.testImplementation.get())
+  extendsFrom(testKitImplementation, configurations.testImplementation.get())
 }
 val funcTestRuntimeOnly: Configuration by configurations.getting {
   extendsFrom(configurations.testRuntimeOnly.get())
@@ -80,6 +80,8 @@ dependencies {
   val mainOutput = sourceSets.main.map { it.output }
   testKitImplementation(mainOutput)
   testKitImplementation(gradleTestKit())
+  testKitImplementation(libs.apache.maven)
+  testKitImplementation(libs.assertk)
 
   testImplementation(testKit.output)
   testImplementation(platform(libs.junit.bom))
diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index 4228ce9d8..487ea9295 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -3,6 +3,7 @@ apache-ant = "org.apache.ant:ant:1.10.15"
 apache-commonsIo = "commons-io:commons-io:2.18.0"
 apache-commonsLang = "org.apache.commons:commons-lang3:3.17.0"
 apache-log4j = "org.apache.logging.log4j:log4j-core:2.24.2"
+apache-maven = "org.apache.maven:maven-repository-metadata:3.9.9"
 asm = "org.ow2.asm:asm-commons:9.7.1"
 jdependency = "org.vafer:jdependency:2.11"
 jdom2 = "org.jdom:jdom2:2.0.6.1"
diff --git a/src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/transformers/PropertiesFileTransformerSpec.groovy b/src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/transformers/PropertiesFileTransformerSpec.groovy
index 6fc067a6b..c479cbb0d 100644
--- a/src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/transformers/PropertiesFileTransformerSpec.groovy
+++ b/src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/transformers/PropertiesFileTransformerSpec.groovy
@@ -22,7 +22,7 @@ package com.github.jengelman.gradle.plugins.shadow.transformers
 import com.github.jengelman.gradle.plugins.shadow.transformers.PropertiesFileTransformer.MergeStrategy
 import spock.lang.Unroll
 
-import static com.github.jengelman.gradle.plugins.shadow.testkit.util.Utils.testObjectFactory
+import static com.github.jengelman.gradle.plugins.shadow.testkit.Utils.testObjectFactory
 import static groovy.lang.Closure.IDENTITY
 
 @Unroll
diff --git a/src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/util/AppendableJar.groovy b/src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/util/AppendableJar.groovy
deleted file mode 100644
index b6fad7012..000000000
--- a/src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/util/AppendableJar.groovy
+++ /dev/null
@@ -1,25 +0,0 @@
-package com.github.jengelman.gradle.plugins.shadow.util
-
-class AppendableJar {
-
-    Map<String, String> contents = [:]
-    File file
-
-    AppendableJar(File file) {
-        this.file = file
-    }
-
-    AppendableJar insertFile(String path, String content) {
-        contents[path] = content
-        return this
-    }
-
-    File write() {
-        JarBuilder builder = new JarBuilder(file.newOutputStream())
-        contents.each { path, contents ->
-            builder.withFile(path, contents)
-        }
-        builder.build()
-        return file
-    }
-}
diff --git a/src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/util/AppendableMavenFileModule.groovy b/src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/util/AppendableMavenFileModule.groovy
index 689f84994..1e4689347 100644
--- a/src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/util/AppendableMavenFileModule.groovy
+++ b/src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/util/AppendableMavenFileModule.groovy
@@ -1,6 +1,7 @@
 package com.github.jengelman.gradle.plugins.shadow.util
 
 import com.github.jengelman.gradle.plugins.shadow.util.repo.maven.MavenFileModule
+import com.github.jengelman.gradle.plugins.shadow.testkit.JarBuilder
 import groovy.transform.InheritConstructors
 import org.apache.commons.io.IOUtils
 
diff --git a/src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/util/HashUtil.java b/src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/util/HashUtil.java
deleted file mode 100644
index b4cb8404d..000000000
--- a/src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/util/HashUtil.java
+++ /dev/null
@@ -1,93 +0,0 @@
-package com.github.jengelman.gradle.plugins.shadow.util;
-
-import org.gradle.api.UncheckedIOException;
-import org.gradle.internal.UncheckedException;
-
-import java.io.ByteArrayInputStream;
-import java.io.File;
-import java.io.FileInputStream;
-import java.io.FileNotFoundException;
-import java.io.IOException;
-import java.io.InputStream;
-import java.security.MessageDigest;
-import java.security.NoSuchAlgorithmException;
-
-public class HashUtil {
-    public static HashValue createHash(File file, String algorithm) {
-        try {
-            return createHash(new FileInputStream(file), algorithm);
-        } catch (UncheckedIOException e) {
-            // Catch any unchecked io exceptions and add the file path for troubleshooting
-            throw new UncheckedIOException(String.format("Failed to create %s hash for file %s.", algorithm, file.getAbsolutePath()), e.getCause());
-        } catch (FileNotFoundException e) {
-            throw new UncheckedIOException(e);
-        }
-    }
-
-    private static HashValue createHash(InputStream instr, String algorithm) {
-        MessageDigest messageDigest;
-        try {
-            messageDigest = createMessageDigest(algorithm);
-            byte[] buffer = new byte[4096];
-            try {
-                while (true) {
-                    int nread = instr.read(buffer);
-                    if (nread < 0) {
-                        break;
-                    }
-                    messageDigest.update(buffer, 0, nread);
-                }
-            } finally {
-                instr.close();
-            }
-        } catch (IOException e) {
-            throw new UncheckedIOException(e);
-        }
-        return new HashValue(messageDigest.digest());
-    }
-
-    private static MessageDigest createMessageDigest(String algorithm) {
-        try {
-            return MessageDigest.getInstance(algorithm);
-        } catch (NoSuchAlgorithmException e) {
-            throw UncheckedException.throwAsUncheckedException(e);
-        }
-    }
-
-    public static HashValue sha1(byte[] bytes) {
-        return createHash(new ByteArrayInputStream(bytes), "SHA1");
-    }
-
-    public static HashValue sha1(InputStream inputStream) {
-        return createHash(inputStream, "SHA1");
-    }
-
-    public static HashValue md5(File file) {
-        return createHash(file, "MD5");
-    }
-
-    public static HashValue sha1(File file) {
-        return createHash(file, "SHA1");
-    }
-
-    public static HashValue sha256(byte[] bytes) {
-        return createHash(new ByteArrayInputStream(bytes), "SHA-256");
-    }
-
-    public static HashValue sha256(InputStream inputStream) {
-        return createHash(inputStream, "SHA-256");
-    }
-
-    public static HashValue sha256(File file) {
-        return createHash(file, "SHA-256");
-    }
-
-    public static HashValue sha512(InputStream inputStream) {
-        return createHash(inputStream, "SHA-512");
-    }
-
-    public static HashValue sha512(File file) {
-        return createHash(file, "SHA-512");
-    }
-}
-
diff --git a/src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/util/HashValue.java b/src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/util/HashValue.java
deleted file mode 100644
index 967afe7ea..000000000
--- a/src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/util/HashValue.java
+++ /dev/null
@@ -1,75 +0,0 @@
-package com.github.jengelman.gradle.plugins.shadow.util;
-
-import java.math.BigInteger;
-
-public class HashValue {
-    private final BigInteger digest;
-
-    public HashValue(byte[] digest) {
-        this.digest = new BigInteger(1, digest);
-    }
-
-    public HashValue(String hexString) {
-        this.digest = new BigInteger(hexString, 16);
-    }
-
-    public static HashValue parse(String inputString) {
-        if (inputString == null || inputString.isEmpty()) {
-            return null;
-        }
-        return new HashValue(parseInput(inputString));
-    }
-
-    private static String parseInput(String inputString) {
-        if (inputString == null) {
-            return null;
-        }
-        String cleaned = inputString.trim().toLowerCase();
-        int spaceIndex = cleaned.indexOf(' ');
-        if (spaceIndex != -1) {
-            String firstPart = cleaned.substring(0, spaceIndex);
-            if (firstPart.startsWith("md") || firstPart.startsWith("sha")) {
-                cleaned = cleaned.substring(cleaned.lastIndexOf(' ') + 1);
-            } else if (firstPart.endsWith(":")) {
-                cleaned = cleaned.substring(spaceIndex + 1).replace(" ", "");
-            } else {
-                cleaned = cleaned.substring(0, spaceIndex);
-            }
-        }
-        return cleaned;
-    }
-
-    public String asCompactString() {
-        return digest.toString(36);
-    }
-
-    public String asHexString() {
-        return digest.toString(16);
-    }
-
-    public byte[] asByteArray() {
-        return digest.toByteArray();
-    }
-
-    public BigInteger asBigInteger() {
-        return digest;
-    }
-
-    @Override
-    public boolean equals(Object other) {
-        if (this == other) {
-            return true;
-        }
-        if (!(other instanceof HashValue)) {
-            return false;
-        }
-
-        HashValue otherHashValue = (HashValue) other;
-        return digest.equals(otherHashValue.digest);
-    }
-
-    @Override
-    public int hashCode() {
-        return digest.hashCode();
-    }
-}
diff --git a/src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/util/JarBuilder.groovy b/src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/util/JarBuilder.groovy
deleted file mode 100644
index b24eb994c..000000000
--- a/src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/util/JarBuilder.groovy
+++ /dev/null
@@ -1,51 +0,0 @@
-package com.github.jengelman.gradle.plugins.shadow.util
-
-import org.codehaus.plexus.util.IOUtil
-
-import java.util.jar.JarEntry
-import java.util.jar.JarOutputStream
-
-class JarBuilder {
-
-    List<String> entries = []
-    JarOutputStream jos
-
-    JarBuilder(OutputStream os) {
-        jos = new JarOutputStream(os)
-    }
-
-    private void addDirectory(String name) {
-        if (!entries.contains(name)) {
-            if (name.lastIndexOf('/') > 0) {
-                String parent = name.substring(0, name.lastIndexOf('/'))
-                if (!entries.contains(parent)) {
-                    addDirectory(parent)
-                }
-            }
-
-            // directory entries must end in "/"
-            JarEntry entry = new JarEntry(name + "/")
-            jos.putNextEntry(entry)
-
-            entries.add(name)
-        }
-    }
-
-    JarBuilder withFile(String path, String data) {
-        def idx = path.lastIndexOf('/')
-        if (idx != -1) {
-            addDirectory(path.substring(0, idx))
-        }
-        if (!entries.contains(path)) {
-            JarEntry entry = new JarEntry(path)
-            jos.putNextEntry(entry)
-            entries << path
-            IOUtil.copy(data.bytes, jos)
-        }
-        return this
-    }
-
-    void build() {
-        jos.close()
-    }
-}
diff --git a/src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/util/PluginSpecification.groovy b/src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/util/PluginSpecification.groovy
index 23b88c502..e77963cb2 100644
--- a/src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/util/PluginSpecification.groovy
+++ b/src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/util/PluginSpecification.groovy
@@ -1,5 +1,6 @@
 package com.github.jengelman.gradle.plugins.shadow.util
 
+import com.github.jengelman.gradle.plugins.shadow.testkit.AppendableJar
 import org.codehaus.plexus.util.IOUtil
 import org.gradle.testkit.runner.BuildResult
 import org.gradle.testkit.runner.GradleRunner
diff --git a/src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/util/repo/AbstractModule.groovy b/src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/util/repo/AbstractModule.groovy
index 7e5b983d0..1f7df9537 100644
--- a/src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/util/repo/AbstractModule.groovy
+++ b/src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/util/repo/AbstractModule.groovy
@@ -1,6 +1,6 @@
 package com.github.jengelman.gradle.plugins.shadow.util.repo
 
-import com.github.jengelman.gradle.plugins.shadow.util.HashUtil
+import com.github.jengelman.gradle.plugins.shadow.testkit.HashUtil
 
 abstract class AbstractModule {
     /**
diff --git a/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/ApacheNoticeResourceTransformerTest.kt b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/ApacheNoticeResourceTransformerTest.kt
index f8cf651ff..014da0387 100644
--- a/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/ApacheNoticeResourceTransformerTest.kt
+++ b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/ApacheNoticeResourceTransformerTest.kt
@@ -4,7 +4,7 @@ import assertk.assertThat
 import assertk.assertions.isFalse
 import assertk.assertions.isTrue
 import assertk.fail
-import com.github.jengelman.gradle.plugins.shadow.testkit.util.testObjectFactory
+import com.github.jengelman.gradle.plugins.shadow.testkit.testObjectFactory
 import org.junit.jupiter.api.BeforeEach
 import org.junit.jupiter.api.Test
 
diff --git a/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/AppendingTransformerTest.kt b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/AppendingTransformerTest.kt
index 681000705..3edfc2743 100644
--- a/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/AppendingTransformerTest.kt
+++ b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/AppendingTransformerTest.kt
@@ -3,7 +3,7 @@ package com.github.jengelman.gradle.plugins.shadow.transformers
 import assertk.assertThat
 import assertk.assertions.isFalse
 import assertk.assertions.isTrue
-import com.github.jengelman.gradle.plugins.shadow.testkit.util.testObjectFactory
+import com.github.jengelman.gradle.plugins.shadow.testkit.testObjectFactory
 import org.junit.jupiter.api.BeforeEach
 import org.junit.jupiter.api.Test
 
diff --git a/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/ManifestAppenderTransformerTest.kt b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/ManifestAppenderTransformerTest.kt
index 935c98da6..ab575c063 100644
--- a/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/ManifestAppenderTransformerTest.kt
+++ b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/ManifestAppenderTransformerTest.kt
@@ -6,7 +6,7 @@ import assertk.assertions.isFalse
 import assertk.assertions.isGreaterThan
 import assertk.assertions.isNotEmpty
 import assertk.assertions.isTrue
-import com.github.jengelman.gradle.plugins.shadow.testkit.util.testObjectFactory
+import com.github.jengelman.gradle.plugins.shadow.testkit.testObjectFactory
 import org.junit.jupiter.api.BeforeEach
 import org.junit.jupiter.api.Test
 
diff --git a/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/PropertiesFileTransformerTest.kt b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/PropertiesFileTransformerTest.kt
index 81e084d43..78100bb5a 100644
--- a/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/PropertiesFileTransformerTest.kt
+++ b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/PropertiesFileTransformerTest.kt
@@ -6,7 +6,7 @@ import assertk.assertions.isEqualTo
 import assertk.assertions.isFalse
 import assertk.assertions.isNotEmpty
 import assertk.assertions.isTrue
-import com.github.jengelman.gradle.plugins.shadow.testkit.util.testObjectFactory
+import com.github.jengelman.gradle.plugins.shadow.testkit.testObjectFactory
 import org.junit.jupiter.api.BeforeEach
 import org.junit.jupiter.api.Test
 
diff --git a/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/XmlAppendingTransformerTest.kt b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/XmlAppendingTransformerTest.kt
index 32895d9fc..22cd28e74 100644
--- a/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/XmlAppendingTransformerTest.kt
+++ b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/XmlAppendingTransformerTest.kt
@@ -3,7 +3,7 @@ package com.github.jengelman.gradle.plugins.shadow.transformers
 import assertk.assertThat
 import assertk.assertions.isFalse
 import assertk.assertions.isTrue
-import com.github.jengelman.gradle.plugins.shadow.testkit.util.testObjectFactory
+import com.github.jengelman.gradle.plugins.shadow.testkit.testObjectFactory
 import org.junit.jupiter.api.BeforeEach
 import org.junit.jupiter.api.Test
 
diff --git a/src/testKit/kotlin/com/github/jengelman/gradle/plugins/shadow/testkit/AppendableJar.kt b/src/testKit/kotlin/com/github/jengelman/gradle/plugins/shadow/testkit/AppendableJar.kt
new file mode 100644
index 000000000..c6cdc9ab8
--- /dev/null
+++ b/src/testKit/kotlin/com/github/jengelman/gradle/plugins/shadow/testkit/AppendableJar.kt
@@ -0,0 +1,20 @@
+package com.github.jengelman.gradle.plugins.shadow.testkit
+
+import java.io.File
+
+class AppendableJar(private val file: File) {
+  private val contents = mutableMapOf<String, String>()
+
+  fun insertFile(path: String, content: String): AppendableJar = apply {
+    contents[path] = content
+  }
+
+  fun write(): File {
+    val builder = JarBuilder(file.outputStream())
+    contents.forEach { (path, content) ->
+      builder.withFile(path, content)
+    }
+    builder.build()
+    return file
+  }
+}
diff --git a/src/testKit/kotlin/com/github/jengelman/gradle/plugins/shadow/testkit/HashUtil.kt b/src/testKit/kotlin/com/github/jengelman/gradle/plugins/shadow/testkit/HashUtil.kt
new file mode 100644
index 000000000..2476bc086
--- /dev/null
+++ b/src/testKit/kotlin/com/github/jengelman/gradle/plugins/shadow/testkit/HashUtil.kt
@@ -0,0 +1,56 @@
+package com.github.jengelman.gradle.plugins.shadow.testkit
+
+import java.io.File
+import java.io.FileInputStream
+import java.io.FileNotFoundException
+import java.io.IOException
+import java.io.InputStream
+import java.security.MessageDigest
+import java.security.NoSuchAlgorithmException
+import org.gradle.api.UncheckedIOException
+import org.gradle.internal.UncheckedException
+
+object HashUtil {
+  @JvmStatic
+  fun createHash(file: File, algorithm: String): HashValue {
+    try {
+      return createHash(FileInputStream(file), algorithm)
+    } catch (e: UncheckedIOException) {
+      // Catch any unchecked io exceptions and add the file path for troubleshooting
+      throw UncheckedIOException(
+        String.format("Failed to create %s hash for file %s.", algorithm, file.absolutePath),
+        e.cause!!,
+      )
+    } catch (e: FileNotFoundException) {
+      throw UncheckedIOException(e)
+    }
+  }
+
+  private fun createHash(inputStream: InputStream, algorithm: String): HashValue {
+    val messageDigest: MessageDigest
+    try {
+      messageDigest = createMessageDigest(algorithm)
+      val buffer = ByteArray(4096)
+      inputStream.use {
+        while (true) {
+          val nread = it.read(buffer)
+          if (nread < 0) {
+            break
+          }
+          messageDigest.update(buffer, 0, nread)
+        }
+      }
+    } catch (e: IOException) {
+      throw UncheckedIOException(e)
+    }
+    return HashValue(messageDigest.digest())
+  }
+
+  private fun createMessageDigest(algorithm: String): MessageDigest {
+    try {
+      return MessageDigest.getInstance(algorithm)
+    } catch (e: NoSuchAlgorithmException) {
+      throw UncheckedException.throwAsUncheckedException(e)
+    }
+  }
+}
diff --git a/src/testKit/kotlin/com/github/jengelman/gradle/plugins/shadow/testkit/HashValue.kt b/src/testKit/kotlin/com/github/jengelman/gradle/plugins/shadow/testkit/HashValue.kt
new file mode 100644
index 000000000..38b3620b4
--- /dev/null
+++ b/src/testKit/kotlin/com/github/jengelman/gradle/plugins/shadow/testkit/HashValue.kt
@@ -0,0 +1,26 @@
+package com.github.jengelman.gradle.plugins.shadow.testkit
+
+import java.math.BigInteger
+
+class HashValue(digest: ByteArray) {
+  private val digest = BigInteger(1, digest)
+
+  fun asBigInteger(): BigInteger {
+    return digest
+  }
+
+  override fun equals(other: Any?): Boolean {
+    if (this === other) {
+      return true
+    }
+    if (other !is HashValue) {
+      return false
+    }
+
+    return digest == other.digest
+  }
+
+  override fun hashCode(): Int {
+    return digest.hashCode()
+  }
+}
diff --git a/src/testKit/kotlin/com/github/jengelman/gradle/plugins/shadow/testkit/JarBuilder.kt b/src/testKit/kotlin/com/github/jengelman/gradle/plugins/shadow/testkit/JarBuilder.kt
new file mode 100644
index 000000000..1f1f61b86
--- /dev/null
+++ b/src/testKit/kotlin/com/github/jengelman/gradle/plugins/shadow/testkit/JarBuilder.kt
@@ -0,0 +1,42 @@
+package com.github.jengelman.gradle.plugins.shadow.testkit
+
+import java.io.OutputStream
+import java.util.jar.JarEntry
+import java.util.jar.JarOutputStream
+
+class JarBuilder(os: OutputStream) {
+  private val entries = mutableListOf<String>()
+  private val jos = JarOutputStream(os)
+
+  private fun addDirectory(name: String) {
+    if (!entries.contains(name)) {
+      val parent = name.substringBeforeLast('/', "")
+      if (parent.isNotEmpty() && !entries.contains(parent)) {
+        addDirectory(parent)
+      }
+
+      // directory entries must end in "/"
+      val entry = JarEntry("$name/")
+      jos.putNextEntry(entry)
+      entries.add(name)
+    }
+  }
+
+  fun withFile(path: String, data: String): JarBuilder {
+    val idx = path.lastIndexOf('/')
+    if (idx != -1) {
+      addDirectory(path.substring(0, idx))
+    }
+    if (!entries.contains(path)) {
+      val entry = JarEntry(path)
+      jos.putNextEntry(entry)
+      entries.add(path)
+      data.toByteArray().inputStream().use { it.copyTo(jos) }
+    }
+    return this
+  }
+
+  fun build() {
+    jos.close()
+  }
+}
diff --git a/src/testKit/kotlin/com/github/jengelman/gradle/plugins/shadow/testkit/util/Utils.kt b/src/testKit/kotlin/com/github/jengelman/gradle/plugins/shadow/testkit/Utils.kt
similarity index 75%
rename from src/testKit/kotlin/com/github/jengelman/gradle/plugins/shadow/testkit/util/Utils.kt
rename to src/testKit/kotlin/com/github/jengelman/gradle/plugins/shadow/testkit/Utils.kt
index 0785681b0..8fbd60b9d 100644
--- a/src/testKit/kotlin/com/github/jengelman/gradle/plugins/shadow/testkit/util/Utils.kt
+++ b/src/testKit/kotlin/com/github/jengelman/gradle/plugins/shadow/testkit/Utils.kt
@@ -1,6 +1,6 @@
 @file:JvmName("Utils")
 
-package com.github.jengelman.gradle.plugins.shadow.testkit.util
+package com.github.jengelman.gradle.plugins.shadow.testkit
 
 import org.gradle.api.model.ObjectFactory
 import org.gradle.testfixtures.ProjectBuilder