diff --git a/build.gradle.kts b/build.gradle.kts
index ee0883ecd..8c1255170 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -66,6 +66,9 @@ val testPluginClasspath by configurations.registering {
   description = "Plugins used in integration tests could be resolved in classpath."
 }
 
+val testKit by sourceSets.creating
+val testKitImplementation by configurations.getting
+
 configurations.configureEach {
   when (name) {
     API_ELEMENTS_CONFIGURATION_NAME,
@@ -115,6 +118,8 @@ dependencies {
   implementation(libs.plexus.utils)
   implementation(libs.plexus.xml)
 
+  testKitImplementation(libs.assertk)
+
   testPluginClasspath(libs.foojayResolver)
   testPluginClasspath(libs.develocity)
   testPluginClasspath(libs.kotlin.kmp)
@@ -172,6 +177,7 @@ testing.suites {
   withType<JvmTestSuite>().configureEach {
     useJUnitJupiter(libs.junit.bom.map { requireNotNull(it.version) })
     dependencies {
+      implementation(testKit.output)
       implementation(libs.assertk)
     }
     targets.configureEach {
diff --git a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/ApplicationPluginTest.kt b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/ApplicationPluginTest.kt
index 1cf0f0b8a..96d56543f 100644
--- a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/ApplicationPluginTest.kt
+++ b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/ApplicationPluginTest.kt
@@ -9,11 +9,11 @@ import assertk.assertions.isEqualTo
 import com.github.jengelman.gradle.plugins.shadow.ShadowApplicationPlugin.Companion.DISTRIBUTION_NAME
 import com.github.jengelman.gradle.plugins.shadow.internal.classPathAttributeKey
 import com.github.jengelman.gradle.plugins.shadow.internal.mainClassAttributeKey
+import com.github.jengelman.gradle.plugins.shadow.testkit.JarPath
+import com.github.jengelman.gradle.plugins.shadow.testkit.containsAtLeast
+import com.github.jengelman.gradle.plugins.shadow.testkit.getContent
+import com.github.jengelman.gradle.plugins.shadow.testkit.getMainAttr
 import com.github.jengelman.gradle.plugins.shadow.util.Issue
-import com.github.jengelman.gradle.plugins.shadow.util.JarPath
-import com.github.jengelman.gradle.plugins.shadow.util.containsAtLeast
-import com.github.jengelman.gradle.plugins.shadow.util.getContent
-import com.github.jengelman.gradle.plugins.shadow.util.getMainAttr
 import com.github.jengelman.gradle.plugins.shadow.util.isWindows
 import com.github.jengelman.gradle.plugins.shadow.util.runProcess
 import java.nio.file.Path
diff --git a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/BasePluginTest.kt b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/BasePluginTest.kt
index 549f34ee9..40217f1d9 100644
--- a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/BasePluginTest.kt
+++ b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/BasePluginTest.kt
@@ -8,13 +8,13 @@ import assertk.assertions.isEqualTo
 import assertk.assertions.isNotNull
 import com.github.jengelman.gradle.plugins.shadow.ShadowApplicationPlugin.Companion.SHADOW_INSTALL_TASK_NAME
 import com.github.jengelman.gradle.plugins.shadow.ShadowApplicationPlugin.Companion.SHADOW_RUN_TASK_NAME
-import com.github.jengelman.gradle.plugins.shadow.internal.requireResourceAsPath
 import com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar
 import com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar.Companion.SHADOW_JAR_TASK_NAME
+import com.github.jengelman.gradle.plugins.shadow.testkit.JarPath
+import com.github.jengelman.gradle.plugins.shadow.testkit.requireResourceAsPath
 import com.github.jengelman.gradle.plugins.shadow.transformers.ResourceTransformer
 import com.github.jengelman.gradle.plugins.shadow.util.AppendableMavenRepository
 import com.github.jengelman.gradle.plugins.shadow.util.JarBuilder
-import com.github.jengelman.gradle.plugins.shadow.util.JarPath
 import com.github.jengelman.gradle.plugins.shadow.util.JvmLang
 import java.io.Closeable
 import java.nio.file.Path
diff --git a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/CachingTest.kt b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/CachingTest.kt
index d2eba7dd6..f2accb91e 100644
--- a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/CachingTest.kt
+++ b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/CachingTest.kt
@@ -6,12 +6,12 @@ import assertk.assertions.isEmpty
 import assertk.assertions.isEqualTo
 import com.github.jengelman.gradle.plugins.shadow.internal.MinimizeDependencyFilter
 import com.github.jengelman.gradle.plugins.shadow.internal.mainClassAttributeKey
+import com.github.jengelman.gradle.plugins.shadow.testkit.JarPath
+import com.github.jengelman.gradle.plugins.shadow.testkit.containsOnly
+import com.github.jengelman.gradle.plugins.shadow.testkit.getMainAttr
 import com.github.jengelman.gradle.plugins.shadow.transformers.ResourceTransformer
 import com.github.jengelman.gradle.plugins.shadow.transformers.ServiceFileTransformer
 import com.github.jengelman.gradle.plugins.shadow.util.Issue
-import com.github.jengelman.gradle.plugins.shadow.util.JarPath
-import com.github.jengelman.gradle.plugins.shadow.util.containsOnly
-import com.github.jengelman.gradle.plugins.shadow.util.getMainAttr
 import kotlin.io.path.ExperimentalPathApi
 import kotlin.io.path.appendText
 import kotlin.io.path.isDirectory
diff --git a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/FilteringTest.kt b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/FilteringTest.kt
index ff35a1e78..04aa43ede 100644
--- a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/FilteringTest.kt
+++ b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/FilteringTest.kt
@@ -1,8 +1,8 @@
 package com.github.jengelman.gradle.plugins.shadow
 
 import assertk.assertThat
+import com.github.jengelman.gradle.plugins.shadow.testkit.containsOnly
 import com.github.jengelman.gradle.plugins.shadow.util.Issue
-import com.github.jengelman.gradle.plugins.shadow.util.containsOnly
 import kotlin.io.path.appendText
 import kotlin.io.path.writeText
 import org.junit.jupiter.api.BeforeEach
diff --git a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/GroovyPluginTest.kt b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/GroovyPluginTest.kt
index bea1706d9..9b406fefa 100644
--- a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/GroovyPluginTest.kt
+++ b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/GroovyPluginTest.kt
@@ -1,8 +1,8 @@
 package com.github.jengelman.gradle.plugins.shadow
 
 import assertk.assertThat
+import com.github.jengelman.gradle.plugins.shadow.testkit.containsOnly
 import com.github.jengelman.gradle.plugins.shadow.util.JvmLang
-import com.github.jengelman.gradle.plugins.shadow.util.containsOnly
 import kotlin.io.path.appendText
 import kotlin.io.path.writeText
 import org.junit.jupiter.api.BeforeEach
diff --git a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/JavaPluginsTest.kt b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/JavaPluginsTest.kt
index 400d843da..90cea057d 100644
--- a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/JavaPluginsTest.kt
+++ b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/JavaPluginsTest.kt
@@ -23,13 +23,13 @@ import com.github.jengelman.gradle.plugins.shadow.internal.runtimeConfiguration
 import com.github.jengelman.gradle.plugins.shadow.legacy.LegacyShadowPlugin
 import com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar
 import com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar.Companion.SHADOW_JAR_TASK_NAME
+import com.github.jengelman.gradle.plugins.shadow.testkit.containsAtLeast
+import com.github.jengelman.gradle.plugins.shadow.testkit.containsNone
+import com.github.jengelman.gradle.plugins.shadow.testkit.containsOnly
+import com.github.jengelman.gradle.plugins.shadow.testkit.getContent
+import com.github.jengelman.gradle.plugins.shadow.testkit.getMainAttr
+import com.github.jengelman.gradle.plugins.shadow.testkit.getStream
 import com.github.jengelman.gradle.plugins.shadow.util.Issue
-import com.github.jengelman.gradle.plugins.shadow.util.containsAtLeast
-import com.github.jengelman.gradle.plugins.shadow.util.containsNone
-import com.github.jengelman.gradle.plugins.shadow.util.containsOnly
-import com.github.jengelman.gradle.plugins.shadow.util.getContent
-import com.github.jengelman.gradle.plugins.shadow.util.getMainAttr
-import com.github.jengelman.gradle.plugins.shadow.util.getStream
 import com.github.jengelman.gradle.plugins.shadow.util.runProcess
 import kotlin.io.path.appendText
 import kotlin.io.path.invariantSeparatorsPathString
diff --git a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/KotlinPluginsTest.kt b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/KotlinPluginsTest.kt
index ad41a3b9d..1122e76de 100644
--- a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/KotlinPluginsTest.kt
+++ b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/KotlinPluginsTest.kt
@@ -5,11 +5,11 @@ import assertk.assertions.contains
 import assertk.assertions.isEqualTo
 import com.github.jengelman.gradle.plugins.shadow.internal.mainClassAttributeKey
 import com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar.Companion.SHADOW_JAR_TASK_NAME
+import com.github.jengelman.gradle.plugins.shadow.testkit.containsAtLeast
+import com.github.jengelman.gradle.plugins.shadow.testkit.containsOnly
+import com.github.jengelman.gradle.plugins.shadow.testkit.getMainAttr
 import com.github.jengelman.gradle.plugins.shadow.util.Issue
 import com.github.jengelman.gradle.plugins.shadow.util.JvmLang
-import com.github.jengelman.gradle.plugins.shadow.util.containsAtLeast
-import com.github.jengelman.gradle.plugins.shadow.util.containsOnly
-import com.github.jengelman.gradle.plugins.shadow.util.getMainAttr
 import kotlin.io.path.appendText
 import kotlin.io.path.writeText
 import org.junit.jupiter.api.BeforeEach
diff --git a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/MinimizeTest.kt b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/MinimizeTest.kt
index b0fda4b83..c33269841 100644
--- a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/MinimizeTest.kt
+++ b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/MinimizeTest.kt
@@ -2,10 +2,10 @@ package com.github.jengelman.gradle.plugins.shadow
 
 import assertk.assertThat
 import com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar.Companion.SHADOW_JAR_TASK_NAME
+import com.github.jengelman.gradle.plugins.shadow.testkit.containsAtLeast
+import com.github.jengelman.gradle.plugins.shadow.testkit.containsNone
+import com.github.jengelman.gradle.plugins.shadow.testkit.containsOnly
 import com.github.jengelman.gradle.plugins.shadow.util.Issue
-import com.github.jengelman.gradle.plugins.shadow.util.containsAtLeast
-import com.github.jengelman.gradle.plugins.shadow.util.containsNone
-import com.github.jengelman.gradle.plugins.shadow.util.containsOnly
 import kotlin.io.path.appendText
 import kotlin.io.path.writeText
 import org.junit.jupiter.api.Test
diff --git a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/PublishingTest.kt b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/PublishingTest.kt
index f3a6c138f..58f3eb93c 100644
--- a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/PublishingTest.kt
+++ b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/PublishingTest.kt
@@ -11,14 +11,14 @@ import assertk.assertions.single
 import com.github.jengelman.gradle.plugins.shadow.ShadowJavaPlugin.Companion.SHADOW_RUNTIME_ELEMENTS_CONFIGURATION_NAME
 import com.github.jengelman.gradle.plugins.shadow.internal.classPathAttributeKey
 import com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar
+import com.github.jengelman.gradle.plugins.shadow.testkit.JarPath
+import com.github.jengelman.gradle.plugins.shadow.testkit.containsAtLeast
+import com.github.jengelman.gradle.plugins.shadow.testkit.containsNone
+import com.github.jengelman.gradle.plugins.shadow.testkit.containsOnly
+import com.github.jengelman.gradle.plugins.shadow.testkit.getMainAttr
 import com.github.jengelman.gradle.plugins.shadow.util.GradleModuleMetadata
 import com.github.jengelman.gradle.plugins.shadow.util.Issue
-import com.github.jengelman.gradle.plugins.shadow.util.JarPath
-import com.github.jengelman.gradle.plugins.shadow.util.containsAtLeast
-import com.github.jengelman.gradle.plugins.shadow.util.containsNone
-import com.github.jengelman.gradle.plugins.shadow.util.containsOnly
 import com.github.jengelman.gradle.plugins.shadow.util.coordinate
-import com.github.jengelman.gradle.plugins.shadow.util.getMainAttr
 import com.squareup.moshi.JsonAdapter
 import com.squareup.moshi.Moshi
 import com.squareup.moshi.kotlin.reflect.KotlinJsonAdapterFactory
diff --git a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/RelocationTest.kt b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/RelocationTest.kt
index b4a56bc68..e2e89cd3b 100644
--- a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/RelocationTest.kt
+++ b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/RelocationTest.kt
@@ -9,9 +9,9 @@ import assertk.assertions.isNotEmpty
 import assertk.fail
 import com.github.jengelman.gradle.plugins.shadow.internal.mainClassAttributeKey
 import com.github.jengelman.gradle.plugins.shadow.tasks.ShadowCopyAction.Companion.CONSTANT_TIME_FOR_ZIP_ENTRIES
+import com.github.jengelman.gradle.plugins.shadow.testkit.containsOnly
+import com.github.jengelman.gradle.plugins.shadow.testkit.getBytes
 import com.github.jengelman.gradle.plugins.shadow.util.Issue
-import com.github.jengelman.gradle.plugins.shadow.util.containsOnly
-import com.github.jengelman.gradle.plugins.shadow.util.getBytes
 import com.github.jengelman.gradle.plugins.shadow.util.runProcess
 import java.net.URLClassLoader
 import kotlin.io.path.appendText
diff --git a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/ScalaPluginTest.kt b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/ScalaPluginTest.kt
index e732701ae..9be358b36 100644
--- a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/ScalaPluginTest.kt
+++ b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/ScalaPluginTest.kt
@@ -1,8 +1,8 @@
 package com.github.jengelman.gradle.plugins.shadow
 
 import assertk.assertThat
+import com.github.jengelman.gradle.plugins.shadow.testkit.containsOnly
 import com.github.jengelman.gradle.plugins.shadow.util.JvmLang
-import com.github.jengelman.gradle.plugins.shadow.util.containsOnly
 import kotlin.io.path.appendText
 import kotlin.io.path.writeText
 import org.junit.jupiter.api.BeforeEach
diff --git a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/AppendingTransformerTest.kt b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/AppendingTransformerTest.kt
index 63bdea05e..a770165b1 100644
--- a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/AppendingTransformerTest.kt
+++ b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/AppendingTransformerTest.kt
@@ -2,7 +2,7 @@ package com.github.jengelman.gradle.plugins.shadow.transformers
 
 import assertk.assertThat
 import assertk.assertions.isEqualTo
-import com.github.jengelman.gradle.plugins.shadow.util.getContent
+import com.github.jengelman.gradle.plugins.shadow.testkit.getContent
 import kotlin.io.path.appendText
 import org.junit.jupiter.params.ParameterizedTest
 import org.junit.jupiter.params.provider.ValueSource
diff --git a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/GroovyExtensionModuleTransformerTest.kt b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/GroovyExtensionModuleTransformerTest.kt
index 2abdc7d52..6b717adce 100644
--- a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/GroovyExtensionModuleTransformerTest.kt
+++ b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/GroovyExtensionModuleTransformerTest.kt
@@ -2,6 +2,8 @@ package com.github.jengelman.gradle.plugins.shadow.transformers
 
 import assertk.assertThat
 import assertk.assertions.isEqualTo
+import com.github.jengelman.gradle.plugins.shadow.testkit.JarPath
+import com.github.jengelman.gradle.plugins.shadow.testkit.getContent
 import com.github.jengelman.gradle.plugins.shadow.transformers.GroovyExtensionModuleTransformer.Companion.KEY_EXTENSION_CLASSES
 import com.github.jengelman.gradle.plugins.shadow.transformers.GroovyExtensionModuleTransformer.Companion.KEY_MODULE_NAME
 import com.github.jengelman.gradle.plugins.shadow.transformers.GroovyExtensionModuleTransformer.Companion.KEY_MODULE_VERSION
@@ -10,8 +12,6 @@ import com.github.jengelman.gradle.plugins.shadow.transformers.GroovyExtensionMo
 import com.github.jengelman.gradle.plugins.shadow.transformers.GroovyExtensionModuleTransformer.Companion.MERGED_MODULE_VERSION
 import com.github.jengelman.gradle.plugins.shadow.transformers.GroovyExtensionModuleTransformer.Companion.PATH_GROOVY_EXTENSION_MODULE_DESCRIPTOR
 import com.github.jengelman.gradle.plugins.shadow.transformers.GroovyExtensionModuleTransformer.Companion.PATH_LEGACY_GROOVY_EXTENSION_MODULE_DESCRIPTOR
-import com.github.jengelman.gradle.plugins.shadow.util.JarPath
-import com.github.jengelman.gradle.plugins.shadow.util.getContent
 import java.nio.file.Path
 import kotlin.io.path.appendText
 import org.junit.jupiter.api.Test
diff --git a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/PropertiesFileTransformerTest.kt b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/PropertiesFileTransformerTest.kt
index f7057d3a8..525f7174f 100644
--- a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/PropertiesFileTransformerTest.kt
+++ b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/PropertiesFileTransformerTest.kt
@@ -3,9 +3,9 @@ package com.github.jengelman.gradle.plugins.shadow.transformers
 import assertk.assertThat
 import assertk.assertions.contains
 import assertk.assertions.isEqualTo
+import com.github.jengelman.gradle.plugins.shadow.testkit.getContent
 import com.github.jengelman.gradle.plugins.shadow.transformers.PropertiesFileTransformer.MergeStrategy
 import com.github.jengelman.gradle.plugins.shadow.util.Issue
-import com.github.jengelman.gradle.plugins.shadow.util.getContent
 import kotlin.io.path.appendText
 import org.junit.jupiter.api.Test
 import org.junit.jupiter.params.ParameterizedTest
diff --git a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/ServiceFileTransformerTest.kt b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/ServiceFileTransformerTest.kt
index 6b1d2fe41..a80d4af57 100644
--- a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/ServiceFileTransformerTest.kt
+++ b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/ServiceFileTransformerTest.kt
@@ -3,8 +3,8 @@ package com.github.jengelman.gradle.plugins.shadow.transformers
 import assertk.assertThat
 import assertk.assertions.containsMatch
 import assertk.assertions.isEqualTo
+import com.github.jengelman.gradle.plugins.shadow.testkit.getContent
 import com.github.jengelman.gradle.plugins.shadow.util.Issue
-import com.github.jengelman.gradle.plugins.shadow.util.getContent
 import kotlin.io.path.appendText
 import kotlin.io.path.writeText
 import org.gradle.api.file.DuplicatesStrategy
diff --git a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/TransformersTest.kt b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/TransformersTest.kt
index d25b713a3..37224074a 100644
--- a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/TransformersTest.kt
+++ b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/TransformersTest.kt
@@ -6,12 +6,12 @@ import assertk.assertions.isEqualTo
 import assertk.assertions.isNotEqualTo
 import assertk.assertions.isNotNull
 import com.github.jengelman.gradle.plugins.shadow.internal.mainClassAttributeKey
-import com.github.jengelman.gradle.plugins.shadow.internal.requireResourceAsPath
+import com.github.jengelman.gradle.plugins.shadow.testkit.containsAtLeast
+import com.github.jengelman.gradle.plugins.shadow.testkit.containsOnly
+import com.github.jengelman.gradle.plugins.shadow.testkit.getContent
+import com.github.jengelman.gradle.plugins.shadow.testkit.getStream
+import com.github.jengelman.gradle.plugins.shadow.testkit.requireResourceAsPath
 import com.github.jengelman.gradle.plugins.shadow.util.Issue
-import com.github.jengelman.gradle.plugins.shadow.util.containsAtLeast
-import com.github.jengelman.gradle.plugins.shadow.util.containsOnly
-import com.github.jengelman.gradle.plugins.shadow.util.getContent
-import com.github.jengelman.gradle.plugins.shadow.util.getStream
 import java.util.jar.Attributes as JarAttribute
 import kotlin.io.path.appendText
 import kotlin.io.path.invariantSeparatorsPathString
diff --git a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/XmlAppendingTransformerTest.kt b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/XmlAppendingTransformerTest.kt
index d35ae4d48..446a9f5c5 100644
--- a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/XmlAppendingTransformerTest.kt
+++ b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/XmlAppendingTransformerTest.kt
@@ -2,8 +2,8 @@ package com.github.jengelman.gradle.plugins.shadow.transformers
 
 import assertk.assertThat
 import assertk.assertions.isEqualTo
+import com.github.jengelman.gradle.plugins.shadow.testkit.getContent
 import com.github.jengelman.gradle.plugins.shadow.util.Issue
-import com.github.jengelman.gradle.plugins.shadow.util.getContent
 import kotlin.io.path.appendText
 import org.junit.jupiter.api.Test
 
diff --git a/src/main/kotlin/com/github/jengelman/gradle/plugins/shadow/internal/Utils.kt b/src/main/kotlin/com/github/jengelman/gradle/plugins/shadow/internal/Utils.kt
index 0acc755eb..708c05efd 100644
--- a/src/main/kotlin/com/github/jengelman/gradle/plugins/shadow/internal/Utils.kt
+++ b/src/main/kotlin/com/github/jengelman/gradle/plugins/shadow/internal/Utils.kt
@@ -3,13 +3,9 @@ package com.github.jengelman.gradle.plugins.shadow.internal
 import com.github.jengelman.gradle.plugins.shadow.tasks.ShadowCopyAction
 import java.io.ByteArrayInputStream
 import java.io.ByteArrayOutputStream
-import java.io.InputStream
 import java.nio.charset.Charset
-import java.nio.file.NoSuchFileException
-import java.nio.file.Path
 import java.util.Properties
 import java.util.jar.Attributes.Name as JarAttributeName
-import kotlin.io.path.toPath
 import org.apache.tools.zip.ZipEntry
 
 /**
@@ -59,16 +55,3 @@ internal fun Properties.inputStream(
   }
   return os.toByteArray().inputStream()
 }
-
-internal fun requireResourceAsStream(name: String): InputStream {
-  return Utils::class.java.classLoader.getResourceAsStream(name)
-    ?: throw NoSuchFileException("Resource $name not found.")
-}
-
-internal fun requireResourceAsPath(name: String): Path {
-  val resource = Utils::class.java.classLoader.getResource(name)
-    ?: throw NoSuchFileException("Resource $name not found.")
-  return resource.toURI().toPath()
-}
-
-private object Utils
diff --git a/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/BaseTransformerTest.kt b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/BaseTransformerTest.kt
index 6e7373e76..e3232b680 100644
--- a/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/BaseTransformerTest.kt
+++ b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/BaseTransformerTest.kt
@@ -1,13 +1,13 @@
 package com.github.jengelman.gradle.plugins.shadow.transformers
 
-import com.github.jengelman.gradle.plugins.shadow.internal.requireResourceAsStream
+import com.github.jengelman.gradle.plugins.shadow.testkit.JarPath
+import com.github.jengelman.gradle.plugins.shadow.testkit.getStream
+import com.github.jengelman.gradle.plugins.shadow.testkit.noOpDelegate
+import com.github.jengelman.gradle.plugins.shadow.testkit.requireResourceAsStream
+import com.github.jengelman.gradle.plugins.shadow.testkit.testObjectFactory
 import com.github.jengelman.gradle.plugins.shadow.transformers.ResourceTransformer.Companion.create
-import com.github.jengelman.gradle.plugins.shadow.util.noOpDelegate
-import com.github.jengelman.gradle.plugins.shadow.util.testObjectFactory
 import java.lang.reflect.ParameterizedType
-import java.nio.file.Path
 import java.util.Locale
-import java.util.zip.ZipFile
 import kotlin.io.path.createTempFile
 import kotlin.io.path.outputStream
 import org.apache.tools.zip.ZipOutputStream
@@ -41,22 +41,19 @@ abstract class BaseTransformerTest<T : ResourceTransformer> {
       return canTransformResource(element)
     }
 
-    fun readFrom(jarPath: Path, resourceName: String = MANIFEST_NAME): List<String> {
-      return ZipFile(jarPath.toFile()).use { zip ->
-        val entry = zip.getEntry(resourceName) ?: return emptyList()
-        zip.getInputStream(entry).bufferedReader().readLines()
-      }
+    fun JarPath.readContentLines(resourceName: String = MANIFEST_NAME): List<String> {
+      return use { it.getStream(resourceName).bufferedReader().readLines() }
     }
 
     fun doTransformAndGetTransformedPath(
       transformer: ResourceTransformer,
       preserveFileTimestamps: Boolean,
-    ): Path {
+    ): JarPath {
       val testableZipPath = createTempFile("testable-zip-file-", ".jar")
-      ZipOutputStream(testableZipPath.outputStream().buffered()).use { zipOutputStream ->
+      ZipOutputStream(testableZipPath.outputStream()).use { zipOutputStream ->
         transformer.modifyOutputStream(zipOutputStream, preserveFileTimestamps)
       }
-      return testableZipPath
+      return JarPath(testableZipPath)
     }
 
     /**
diff --git a/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/ComponentsXmlResourceTransformerTest.kt b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/ComponentsXmlResourceTransformerTest.kt
index a610285f2..3abea396c 100644
--- a/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/ComponentsXmlResourceTransformerTest.kt
+++ b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/ComponentsXmlResourceTransformerTest.kt
@@ -2,7 +2,7 @@ package com.github.jengelman.gradle.plugins.shadow.transformers
 
 import assertk.assertThat
 import assertk.assertions.isTrue
-import com.github.jengelman.gradle.plugins.shadow.internal.requireResourceAsStream
+import com.github.jengelman.gradle.plugins.shadow.testkit.requireResourceAsStream
 import org.custommonkey.xmlunit.XMLUnit
 import org.junit.jupiter.api.Test
 
diff --git a/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/Log4j2PluginsCacheFileTransformerTest.kt b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/Log4j2PluginsCacheFileTransformerTest.kt
index af582e74f..45ea7c5fb 100644
--- a/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/Log4j2PluginsCacheFileTransformerTest.kt
+++ b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/Log4j2PluginsCacheFileTransformerTest.kt
@@ -8,11 +8,11 @@ import assertk.assertions.isNotEqualTo
 import assertk.assertions.isTrue
 import assertk.assertions.startsWith
 import assertk.fail
-import com.github.jengelman.gradle.plugins.shadow.internal.requireResourceAsPath
-import com.github.jengelman.gradle.plugins.shadow.internal.requireResourceAsStream
 import com.github.jengelman.gradle.plugins.shadow.relocation.Relocator
 import com.github.jengelman.gradle.plugins.shadow.relocation.SimpleRelocator
-import com.github.jengelman.gradle.plugins.shadow.util.zipOutputStream
+import com.github.jengelman.gradle.plugins.shadow.testkit.requireResourceAsPath
+import com.github.jengelman.gradle.plugins.shadow.testkit.requireResourceAsStream
+import com.github.jengelman.gradle.plugins.shadow.testkit.zipOutputStream
 import java.io.ByteArrayOutputStream
 import java.net.URI
 import java.net.URL
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 d4de4d1d3..53a0c690f 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.internal.requireResourceAsStream
+import com.github.jengelman.gradle.plugins.shadow.testkit.requireResourceAsStream
 import org.junit.jupiter.api.Test
 
 class ManifestAppenderTransformerTest : BaseTransformerTest<ManifestAppenderTransformer>() {
@@ -44,9 +44,7 @@ class ManifestAppenderTransformerTest : BaseTransformerTest<ManifestAppenderTran
       transform(manifestTransformerContext)
     }
 
-    val testableZipPath = doTransformAndGetTransformedPath(transformer, true)
-
-    val targetLines = readFrom(testableZipPath)
+    val targetLines = doTransformAndGetTransformedPath(transformer, true).readContentLines()
     assertThat(targetLines).isNotEmpty()
     assertThat(targetLines.size).isGreaterThan(4)
 
@@ -66,8 +64,7 @@ class ManifestAppenderTransformerTest : BaseTransformerTest<ManifestAppenderTran
   fun noTransformation() {
     val sourceLines = requireResourceAsStream(MANIFEST_NAME).bufferedReader().readLines()
     transformer.transform(manifestTransformerContext)
-    val testableZipPath = doTransformAndGetTransformedPath(transformer, true)
-    val targetLines = readFrom(testableZipPath)
+    val targetLines = doTransformAndGetTransformedPath(transformer, true).readContentLines()
 
     assertThat(targetLines).isEqualTo(sourceLines)
   }
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 f6b013f5d..a51818829 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
@@ -32,8 +32,7 @@ class PropertiesFileTransformerTest : BaseTransformerTest<PropertiesFileTransfor
   fun transformation() {
     transformer.transform(manifestTransformerContext)
 
-    val testableZipPath = doTransformAndGetTransformedPath(transformer, false)
-    val targetLines = readFrom(testableZipPath)
+    val targetLines = doTransformAndGetTransformedPath(transformer, false).readContentLines()
 
     assertThat(targetLines).isNotEmpty()
     assertThat(targetLines).contains("Manifest-Version=1.0")
@@ -43,13 +42,9 @@ class PropertiesFileTransformerTest : BaseTransformerTest<PropertiesFileTransfor
   fun transformationPropertiesAreReproducible() {
     transformer.transform(manifestTransformerContext)
 
-    val firstRunTransformedPath = doTransformAndGetTransformedPath(transformer, true)
-    val firstRunTargetLines = readFrom(firstRunTransformedPath)
-
+    val firstRunTargetLines = doTransformAndGetTransformedPath(transformer, true).readContentLines()
     Thread.sleep(1000) // wait for 1sec to ensure timestamps in properties would change
-
-    val secondRunTransformedPath = doTransformAndGetTransformedPath(transformer, true)
-    val secondRunTargetLines = readFrom(secondRunTransformedPath)
+    val secondRunTargetLines = doTransformAndGetTransformedPath(transformer, true).readContentLines()
 
     assertThat(firstRunTargetLines).isEqualTo(secondRunTargetLines)
   }
diff --git a/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/ServiceFileTransformerTest.kt b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/ServiceFileTransformerTest.kt
index 7fb5c2616..971f2afff 100644
--- a/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/ServiceFileTransformerTest.kt
+++ b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/ServiceFileTransformerTest.kt
@@ -6,10 +6,10 @@ import assertk.assertions.isFalse
 import assertk.assertions.isTrue
 import com.github.jengelman.gradle.plugins.shadow.relocation.Relocator
 import com.github.jengelman.gradle.plugins.shadow.relocation.SimpleRelocator
-import com.github.jengelman.gradle.plugins.shadow.util.zipOutputStream
-import java.io.InputStream
+import com.github.jengelman.gradle.plugins.shadow.testkit.JarPath
+import com.github.jengelman.gradle.plugins.shadow.testkit.getContent
+import com.github.jengelman.gradle.plugins.shadow.testkit.zipOutputStream
 import java.nio.file.Path
-import java.util.zip.ZipFile
 import kotlin.io.path.createTempFile
 import kotlin.io.path.deleteExisting
 import kotlin.io.path.outputStream
@@ -86,7 +86,7 @@ class ServiceFileTransformerTest : BaseTransformerTest<ServiceFileTransformer>()
       transformer.modifyOutputStream(zos, false)
     }
 
-    val transformedContent = ZipFile(tempJar.toFile()).use { it.getContent(contentResourceShaded) }
+    val transformedContent = JarPath(tempJar).use { it.getContent(contentResourceShaded) }
     assertThat(transformedContent).isEqualTo("borg.foo.Service\norg.foo.exclude.OtherService")
   }
 
@@ -105,7 +105,7 @@ class ServiceFileTransformerTest : BaseTransformerTest<ServiceFileTransformer>()
       transformer.modifyOutputStream(zos, false)
     }
 
-    val transformedContent = ZipFile(tempJar.toFile()).use { it.getContent(contentResourceShaded) }
+    val transformedContent = JarPath(tempJar).use { it.getContent(contentResourceShaded) }
     assertThat(transformedContent).isEqualTo("borg.foo.Service\norg.foo.exclude.OtherService")
   }
 
@@ -122,7 +122,7 @@ class ServiceFileTransformerTest : BaseTransformerTest<ServiceFileTransformer>()
       transformer.modifyOutputStream(zos, false)
     }
 
-    val transformedContent = ZipFile(tempJar.toFile()).use { it.getContent(contentResource) }
+    val transformedContent = JarPath(tempJar).use { it.getContent(contentResource) }
     assertThat(transformedContent).isEqualTo("org.eclipse1234.osgi.launch.EquinoxFactory")
   }
 
@@ -144,7 +144,7 @@ class ServiceFileTransformerTest : BaseTransformerTest<ServiceFileTransformer>()
       transformer.modifyOutputStream(zos, false)
     }
 
-    val transformedContent = ZipFile(tempJar.toFile()).use { it.getContent(contentResource) }
+    val transformedContent = JarPath(tempJar).use { it.getContent(contentResource) }
     assertThat(transformedContent).isEqualTo("borg.foo.Service\norg.blah.Service")
   }
 
@@ -153,15 +153,6 @@ class ServiceFileTransformerTest : BaseTransformerTest<ServiceFileTransformer>()
       return TransformerContext(path, input.byteInputStream(), relocators = relocators.toSet())
     }
 
-    fun ZipFile.getContent(entryName: String): String {
-      return getStream(entryName).bufferedReader().use { it.readText() }
-    }
-
-    fun ZipFile.getStream(entryName: String): InputStream {
-      val entry = requireNotNull(getEntry(entryName)) { "Entry $entryName not found in all entries: ${entries().toList()}" }
-      return getInputStream(entry)
-    }
-
     @JvmStatic
     fun resourceProvider() = listOf(
       // path, exclude, expected
diff --git a/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/util/Utils.kt b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/util/Utils.kt
index 0f7168379..53e52179c 100644
--- a/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/util/Utils.kt
+++ b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/util/Utils.kt
@@ -1,4 +1,4 @@
-package com.github.jengelman.gradle.plugins.shadow.util
+package com.github.jengelman.gradle.plugins.shadow.testkit
 
 import java.io.OutputStream
 import java.lang.reflect.InvocationHandler
diff --git a/src/test/resources/META-INF/org/apache/logging/log4j/core/config/plugins/Log4j2Plugins.dat b/src/test/resources/META-INF/org/apache/logging/log4j/core/config/plugins/Log4j2Plugins.dat
deleted file mode 100644
index fbe6359f1..000000000
Binary files a/src/test/resources/META-INF/org/apache/logging/log4j/core/config/plugins/Log4j2Plugins.dat and /dev/null differ
diff --git a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/util/JarPath.kt b/src/testKit/kotlin/com/github/jengelman/gradle/plugins/shadow/testkit/JarPath.kt
similarity index 97%
rename from src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/util/JarPath.kt
rename to src/testKit/kotlin/com/github/jengelman/gradle/plugins/shadow/testkit/JarPath.kt
index 214edce89..a213bc939 100644
--- a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/util/JarPath.kt
+++ b/src/testKit/kotlin/com/github/jengelman/gradle/plugins/shadow/testkit/JarPath.kt
@@ -1,4 +1,4 @@
-package com.github.jengelman.gradle.plugins.shadow.util
+package com.github.jengelman.gradle.plugins.shadow.testkit
 
 import assertk.Assert
 import assertk.assertions.containsAtLeast
diff --git a/src/testKit/kotlin/com/github/jengelman/gradle/plugins/shadow/testkit/Resource.kt b/src/testKit/kotlin/com/github/jengelman/gradle/plugins/shadow/testkit/Resource.kt
new file mode 100644
index 000000000..0f20ebee3
--- /dev/null
+++ b/src/testKit/kotlin/com/github/jengelman/gradle/plugins/shadow/testkit/Resource.kt
@@ -0,0 +1,19 @@
+package com.github.jengelman.gradle.plugins.shadow.testkit
+
+import java.io.InputStream
+import java.nio.file.NoSuchFileException
+import java.nio.file.Path
+import kotlin.io.path.toPath
+
+fun requireResourceAsStream(name: String): InputStream {
+  return Utils::class.java.classLoader.getResourceAsStream(name)
+    ?: throw NoSuchFileException("Resource $name not found.")
+}
+
+fun requireResourceAsPath(name: String): Path {
+  val resource = Utils::class.java.classLoader.getResource(name)
+    ?: throw NoSuchFileException("Resource $name not found.")
+  return resource.toURI().toPath()
+}
+
+private object Utils
diff --git a/src/functionalTest/resources/META-INF/org/apache/logging/log4j/core/config/plugins/Log4j2Plugins.dat b/src/testKit/resources/META-INF/org/apache/logging/log4j/core/config/plugins/Log4j2Plugins.dat
similarity index 100%
rename from src/functionalTest/resources/META-INF/org/apache/logging/log4j/core/config/plugins/Log4j2Plugins.dat
rename to src/testKit/resources/META-INF/org/apache/logging/log4j/core/config/plugins/Log4j2Plugins.dat