diff --git a/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/internal/BytecodeRemappingTest.kt b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/internal/BytecodeRemappingTest.kt
index c3f41ea59..9bbb3c7d6 100644
--- a/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/internal/BytecodeRemappingTest.kt
+++ b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/internal/BytecodeRemappingTest.kt
@@ -1,9 +1,12 @@
 package com.github.jengelman.gradle.plugins.shadow.internal
 
+import assertk.assertFailure
 import assertk.assertThat
 import assertk.assertions.contains
 import assertk.assertions.doesNotContain
+import assertk.assertions.hasMessage
 import assertk.assertions.isEqualTo
+import assertk.assertions.isInstanceOf
 import com.github.jengelman.gradle.plugins.shadow.relocation.SimpleRelocator
 import com.github.jengelman.gradle.plugins.shadow.testkit.requireResourceAsPath
 import com.github.jengelman.gradle.plugins.shadow.util.noOpDelegate
@@ -15,7 +18,6 @@ import kotlin.reflect.KClass
 import org.gradle.api.GradleException
 import org.gradle.api.file.FileCopyDetails
 import org.junit.jupiter.api.Test
-import org.junit.jupiter.api.assertThrows
 import org.junit.jupiter.api.io.TempDir
 import org.junit.jupiter.params.ParameterizedTest
 import org.junit.jupiter.params.provider.ValueSource
@@ -75,9 +77,9 @@ class BytecodeRemappingTest {
         override fun getFile(): File = file
       }
 
-    val failure = assertThrows<GradleException> { details.remapClass(relocators) }
-
-    assertThat(failure.message).isEqualTo("Error in ASM processing class $path")
+    assertFailure { details.remapClass(relocators) }
+      .isInstanceOf<GradleException>()
+      .hasMessage("Error in ASM processing class $path")
   }
 
   @Test
diff --git a/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/internal/DefaultDependencyFilterTest.kt b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/internal/DefaultDependencyFilterTest.kt
index 18b63496e..3d756a4e9 100644
--- a/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/internal/DefaultDependencyFilterTest.kt
+++ b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/internal/DefaultDependencyFilterTest.kt
@@ -1,14 +1,16 @@
 package com.github.jengelman.gradle.plugins.shadow.internal
 
+import assertk.assertFailure
 import assertk.assertThat
 import assertk.assertions.contains
 import assertk.assertions.isEqualTo
+import assertk.assertions.isInstanceOf
 import assertk.assertions.isTrue
+import assertk.assertions.messageContains
 import com.github.jengelman.gradle.plugins.shadow.util.noOpDelegate
 import org.gradle.api.artifacts.ResolvedDependency
 import org.gradle.testfixtures.ProjectBuilder
 import org.junit.jupiter.api.Test
-import org.junit.jupiter.api.assertThrows
 import org.junit.jupiter.params.ParameterizedTest
 import org.junit.jupiter.params.provider.Arguments
 import org.junit.jupiter.params.provider.MethodSource
@@ -47,10 +49,9 @@ class DefaultDependencyFilterTest {
 
   @Test
   fun rejectsUnsupportedProjectNotation() {
-    val failure = assertThrows<IllegalArgumentException> { filter.project(42) }
-
-    assertThat(failure.message.orEmpty())
-      .contains("Unsupported notation type: class java.lang.Integer")
+    assertFailure { filter.project(42) }
+      .isInstanceOf<IllegalArgumentException>()
+      .messageContains("Unsupported notation type: class java.lang.Integer")
   }
 
   private companion object {
diff --git a/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/internal/ZipEntryValidationTest.kt b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/internal/ZipEntryValidationTest.kt
index a24c0650c..6112e3734 100644
--- a/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/internal/ZipEntryValidationTest.kt
+++ b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/internal/ZipEntryValidationTest.kt
@@ -1,7 +1,10 @@
 package com.github.jengelman.gradle.plugins.shadow.internal
 
+import assertk.assertFailure
 import assertk.assertThat
+import assertk.assertions.hasMessage
 import assertk.assertions.isEqualTo
+import assertk.assertions.isInstanceOf
 import assertk.assertions.isTrue
 import com.github.jengelman.gradle.plugins.shadow.util.zipOutputStream
 import java.io.ByteArrayOutputStream
@@ -13,7 +16,6 @@ import org.apache.tools.zip.ZipFile
 import org.apache.tools.zip.ZipOutputStream
 import org.gradle.api.GradleException
 import org.junit.jupiter.api.Test
-import org.junit.jupiter.api.assertThrows
 import org.junit.jupiter.api.io.TempDir
 
 class ZipEntryValidationTest {
@@ -114,12 +116,11 @@ class ZipEntryValidationTest {
       )
 
     for (name in maliciousNames) {
-      val exception =
-        assertThrows<GradleException> {
+      assertFailure {
           ByteArrayOutputStream().zipOutputStream().use { it.writeEntry(name) }
         }
-      assertThat(exception.message)
-        .isEqualTo("Malicious ZIP entry containing path traversal sequence: $name")
+        .isInstanceOf<GradleException>()
+        .hasMessage("Malicious ZIP entry containing path traversal sequence: $name")
     }
   }
 }
diff --git a/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/DeduplicatingResourceTransformerTest.kt b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/DeduplicatingResourceTransformerTest.kt
index 803a0be6f..d129e5efe 100644
--- a/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/DeduplicatingResourceTransformerTest.kt
+++ b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/DeduplicatingResourceTransformerTest.kt
@@ -1,10 +1,13 @@
 package com.github.jengelman.gradle.plugins.shadow.transformers
 
+import assertk.assertFailure
 import assertk.assertThat
 import assertk.assertions.containsExactlyInAnyOrder
 import assertk.assertions.containsOnly
+import assertk.assertions.hasMessage
 import assertk.assertions.isEqualTo
 import assertk.assertions.isFalse
+import assertk.assertions.isInstanceOf
 import assertk.assertions.isTrue
 import com.github.jengelman.gradle.plugins.shadow.transformers.DeduplicatingResourceTransformer.Companion.sha256Hex
 import com.github.jengelman.gradle.plugins.shadow.util.zipOutputStream
@@ -13,7 +16,6 @@ import kotlin.io.path.writeText
 import org.gradle.api.GradleException
 import org.junit.jupiter.api.BeforeEach
 import org.junit.jupiter.api.Test
-import org.junit.jupiter.api.assertThrows
 import org.junit.jupiter.params.ParameterizedTest
 import org.junit.jupiter.params.provider.ValueSource
 
@@ -119,15 +121,13 @@ class DeduplicatingResourceTransformerTest :
       canTransformResource("differing-content", file1)
       canTransformResource("differing-content", file3)
 
-      val failure =
-        assertThrows<GradleException> {
+      assertFailure {
           tempJar.zipOutputStream().use {
             modifyOutputStream(it, false)
           }
         }
-
-      assertThat(failure.message.orEmpty())
-        .isEqualTo(
+        .isInstanceOf<GradleException>()
+        .hasMessage(
           """
           |Found 1 path duplicate(s) with different content in the shadowed JAR:
           |  * differing-content
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 bbd2064fb..ec63cbbac 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
@@ -1,9 +1,12 @@
 package com.github.jengelman.gradle.plugins.shadow.transformers
 
+import assertk.assertFailure
 import assertk.assertThat
 import assertk.assertions.contains
+import assertk.assertions.hasMessage
 import assertk.assertions.isEqualTo
 import assertk.assertions.isFalse
+import assertk.assertions.isInstanceOf
 import assertk.assertions.isTrue
 import com.github.jengelman.gradle.plugins.shadow.internal.inputStream
 import com.github.jengelman.gradle.plugins.shadow.testkit.JarPath
@@ -16,7 +19,6 @@ import java.nio.charset.Charset
 import java.util.Properties
 import org.gradle.api.GradleException
 import org.junit.jupiter.api.Test
-import org.junit.jupiter.api.assertThrows
 import org.junit.jupiter.params.ParameterizedTest
 import org.junit.jupiter.params.provider.Arguments
 import org.junit.jupiter.params.provider.MethodSource
@@ -70,10 +72,9 @@ class PropertiesFileTransformerTest : BaseTransformerTest<PropertiesFileTransfor
       transform(context(path, mapOf("foo" to "foo")))
       transform(context(path, mapOf("foo" to "bar")))
 
-      val failure = assertThrows<GradleException> { transformToJar() }
-
-      assertThat(failure.message.orEmpty())
-        .isEqualTo(
+      assertFailure { transformToJar() }
+        .isInstanceOf<GradleException>()
+        .hasMessage(
           """
           |The following properties files have conflicting property values and cannot be merged:
           | * f.properties