diff --git a/test/unit/org/apache/cassandra/db/marshal/TypeParserTest.java b/test/unit/org/apache/cassandra/db/marshal/TypeParserTest.java
index 44cc5b2aea..46a2a5af9a 100644
--- a/test/unit/org/apache/cassandra/db/marshal/TypeParserTest.java
+++ b/test/unit/org/apache/cassandra/db/marshal/TypeParserTest.java
@@ -21,9 +21,9 @@ package org.apache.cassandra.db.marshal;
 import org.junit.BeforeClass;
 import org.junit.Test;
 
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertSame;
-import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 
 import org.apache.cassandra.config.DatabaseDescriptor;
@@ -45,15 +45,9 @@ public class TypeParserTest
     public void testRejectsNonAbstractTypeWithoutInitializing() throws SyntaxException
     {
         ClassLoadingTestSupport.assertNotInitialized(ClassLoadingTestNonAssignable.class);
-        try
-        {
-            TypeParser.parse(ClassLoadingTestNonAssignable.class.getName());
-            fail("Should not pass");
-        }
-        catch (ConfigurationException e)
-        {
-            assertTrue(e.getMessage().contains("must extend or implement " + AbstractType.class.getName()));
-        }
+        assertThatThrownBy(() -> TypeParser.parse(ClassLoadingTestNonAssignable.class.getName()))
+        .isInstanceOf(ConfigurationException.class)
+        .hasMessageContaining("must extend or implement " + AbstractType.class.getName());
 
         assertFalse(ClassLoadingTestSupport.wasInitialized(ClassLoadingTestNonAssignable.class));
     }
diff --git a/test/unit/org/apache/cassandra/diag/DiagnosticEventPersistenceTest.java b/test/unit/org/apache/cassandra/diag/DiagnosticEventPersistenceTest.java
index b18d7b6aac..9315054d61 100644
--- a/test/unit/org/apache/cassandra/diag/DiagnosticEventPersistenceTest.java
+++ b/test/unit/org/apache/cassandra/diag/DiagnosticEventPersistenceTest.java
@@ -28,7 +28,7 @@ import org.apache.cassandra.utils.ClassLoadingTestNonAssignable;
 import org.apache.cassandra.utils.ClassLoadingTestSupport;
 
 import static org.assertj.core.api.Assertions.assertThat;
-import static org.junit.Assert.fail;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
 
 public class DiagnosticEventPersistenceTest
 {
@@ -55,15 +55,9 @@ public class DiagnosticEventPersistenceTest
     {
         ClassLoadingTestSupport.assertNotInitialized(ClassLoadingTestNonAssignable.class);
 
-        try
-        {
-            getEventClass(ClassLoadingTestNonAssignable.class.getName());
-            fail("Expected InvalidClassException for a non-DiagnosticEvent class");
-        }
-        catch (InvalidClassException e)
-        {
-            assertThat(e.getMessage()).contains("must be of type DiagnosticEvent");
-        }
+        assertThatThrownBy(() -> getEventClass(ClassLoadingTestNonAssignable.class.getName()))
+        .isInstanceOf(InvalidClassException.class)
+        .hasMessageContaining("must be of type DiagnosticEvent");
 
         assertThat(ClassLoadingTestSupport.wasInitialized(ClassLoadingTestNonAssignable.class)).isFalse();
     }
diff --git a/test/unit/org/apache/cassandra/index/SecondaryIndexManagerTest.java b/test/unit/org/apache/cassandra/index/SecondaryIndexManagerTest.java
index eff70b5be9..29389b84d3 100644
--- a/test/unit/org/apache/cassandra/index/SecondaryIndexManagerTest.java
+++ b/test/unit/org/apache/cassandra/index/SecondaryIndexManagerTest.java
@@ -46,6 +46,7 @@ import org.apache.cassandra.utils.JVMStabilityInspector;
 import org.apache.cassandra.utils.KillerForTests;
 import org.apache.cassandra.utils.concurrent.Refs;
 
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
@@ -64,15 +65,9 @@ public class SecondaryIndexManagerTest extends CQLTester
     public void rejectsNonIndexClassWithoutInitializing()
     {
         ClassLoadingTestSupport.assertNotInitialized(ClassLoadingTestNonAssignable.class);
-        try
-        {
-            SecondaryIndexManager.loadIndexClass(ClassLoadingTestNonAssignable.class.getName());
-            fail("Should not pass");
-        }
-        catch (ConfigurationException e)
-        {
-            assertTrue(e.getMessage().contains("must extend or implement " + Index.class.getName()));
-        }
+        assertThatThrownBy(() -> SecondaryIndexManager.loadIndexClass(ClassLoadingTestNonAssignable.class.getName()))
+        .isInstanceOf(ConfigurationException.class)
+        .hasMessageContaining("must extend or implement " + Index.class.getName());
 
         assertFalse(ClassLoadingTestSupport.wasInitialized(ClassLoadingTestNonAssignable.class));
     }
diff --git a/test/unit/org/apache/cassandra/index/sasi/conf/IndexModeTest.java b/test/unit/org/apache/cassandra/index/sasi/conf/IndexModeTest.java
index 8a6e464413..4669433888 100644
--- a/test/unit/org/apache/cassandra/index/sasi/conf/IndexModeTest.java
+++ b/test/unit/org/apache/cassandra/index/sasi/conf/IndexModeTest.java
@@ -39,6 +39,8 @@ import org.apache.cassandra.utils.ByteBufferUtil;
 import org.apache.cassandra.utils.ClassLoadingTestNonAssignable;
 import org.apache.cassandra.utils.ClassLoadingTestSupport;
 
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
 
 public class IndexModeTest
 {
@@ -217,15 +219,9 @@ public class IndexModeTest
         ColumnMetadata cd = ColumnMetadata.regularColumn(cfm, ByteBufferUtil.bytes("TestColumnMetadata"), BytesType.instance);
 
         ClassLoadingTestSupport.assertNotInitialized(ClassLoadingTestNonAssignable.class);
-        try
-        {
-            IndexMode.getMode(cd, Collections.singletonMap("analyzer_class", ClassLoadingTestNonAssignable.class.getName()));
-            Assert.fail("Should not pass");
-        }
-        catch (ConfigurationException e)
-        {
-            Assert.assertTrue(e.getMessage().contains("must extend or implement " + AbstractAnalyzer.class.getName()));
-        }
+        assertThatThrownBy(() -> IndexMode.getMode(cd, Collections.singletonMap("analyzer_class", ClassLoadingTestNonAssignable.class.getName())))
+        .isInstanceOf(ConfigurationException.class)
+        .hasMessageContaining("must extend or implement " + AbstractAnalyzer.class.getName());
 
         Assert.assertFalse(ClassLoadingTestSupport.wasInitialized(ClassLoadingTestNonAssignable.class));
     }
@@ -249,15 +245,9 @@ public class IndexModeTest
         ColumnMetadata cd = ColumnMetadata.regularColumn(cfm, ByteBufferUtil.bytes("TestColumnMetadata"), UTF8Type.instance);
 
         ClassLoadingTestSupport.assertNotInitialized(ClassLoadingTestNonAssignable.class);
-        try
-        {
-            IndexMode.validateAnalyzer(Collections.singletonMap("analyzer_class", ClassLoadingTestNonAssignable.class.getName()), cd);
-            Assert.fail("Should not pass");
-        }
-        catch (ConfigurationException e)
-        {
-            Assert.assertTrue(e.getMessage().contains("must extend or implement " + AbstractAnalyzer.class.getName()));
-        }
+        assertThatThrownBy(() -> IndexMode.validateAnalyzer(Collections.singletonMap("analyzer_class", ClassLoadingTestNonAssignable.class.getName()), cd))
+        .isInstanceOf(ConfigurationException.class)
+        .hasMessageContaining("must extend or implement " + AbstractAnalyzer.class.getName());
 
         Assert.assertFalse(ClassLoadingTestSupport.wasInitialized(ClassLoadingTestNonAssignable.class));
     }
diff --git a/test/unit/org/apache/cassandra/security/CipherFactoryTest.java b/test/unit/org/apache/cassandra/security/CipherFactoryTest.java
index 9d58df8502..2399a0d859 100644
--- a/test/unit/org/apache/cassandra/security/CipherFactoryTest.java
+++ b/test/unit/org/apache/cassandra/security/CipherFactoryTest.java
@@ -39,6 +39,7 @@ import org.apache.cassandra.utils.ClassLoadingTestNonAssignable;
 import org.apache.cassandra.utils.ClassLoadingTestSupport;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.fail;
 
@@ -52,19 +53,11 @@ public class CipherFactoryTest
         TransparentDataEncryptionOptions options = EncryptionContextGenerator.createEncryptionOptions();
         options.key_provider.class_name = ClassLoadingTestNonAssignable.class.getName();
 
-        try
-        {
-            new CipherFactory(options);
-            fail("Expected CipherFactory construction to be rejected for a non-KeyProvider class");
-        }
-        catch (RuntimeException e)
-        {
-            // CipherFactory wraps the load failure; the cause is the type-check ConfigurationException
-            Throwable cause = e.getCause();
-            assertNotNull(cause);
-            assertThat(cause).isInstanceOf(ConfigurationException.class);
-            assertThat(cause.getMessage()).contains("must extend or implement " + KeyProvider.class.getName());
-        }
+        // CipherFactory wraps the load failure; the cause is the type-check ConfigurationException
+        assertThatThrownBy(() -> new CipherFactory(options))
+        .isInstanceOf(RuntimeException.class)
+        .hasCauseInstanceOf(ConfigurationException.class)
+        .hasStackTraceContaining("must extend or implement " + KeyProvider.class.getName());
 
         assertThat(ClassLoadingTestSupport.wasInitialized(ClassLoadingTestNonAssignable.class)).isFalse();
     }
diff --git a/test/unit/org/apache/cassandra/utils/FBUtilitiesTest.java b/test/unit/org/apache/cassandra/utils/FBUtilitiesTest.java
index d33f0970b3..e32bf7d74d 100644
--- a/test/unit/org/apache/cassandra/utils/FBUtilitiesTest.java
+++ b/test/unit/org/apache/cassandra/utils/FBUtilitiesTest.java
@@ -49,9 +49,9 @@ import org.apache.cassandra.config.Config;
 import org.apache.cassandra.config.DatabaseDescriptor;
 import org.apache.cassandra.exceptions.ConfigurationException;
 
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 
 public class FBUtilitiesTest
@@ -60,15 +60,9 @@ public class FBUtilitiesTest
     public void testTypedClassForNameRejectsWithoutInitializing()
     {
         ClassLoadingTestSupport.assertNotInitialized(ClassLoadingTestNonAssignable.class);
-        try
-        {
-            FBUtilities.classForNameWithoutInitialization(ClassLoadingTestNonAssignable.class.getName(), "test class", Runnable.class);
-            fail("Should not pass");
-        }
-        catch (ConfigurationException e)
-        {
-            assertTrue(e.getMessage().contains("must extend or implement " + Runnable.class.getName()));
-        }
+        assertThatThrownBy(() -> FBUtilities.classForNameWithoutInitialization(ClassLoadingTestNonAssignable.class.getName(), "test class", Runnable.class))
+        .isInstanceOf(ConfigurationException.class)
+        .hasMessageContaining("must extend or implement " + Runnable.class.getName());
 
         assertFalse(ClassLoadingTestSupport.wasInitialized(ClassLoadingTestNonAssignable.class));
     }
@@ -77,15 +71,9 @@ public class FBUtilitiesTest
     public void testTypedConstructRejectsWithoutInitializing()
     {
         ClassLoadingTestSupport.assertNotInitialized(ClassLoadingTestNonAssignable.class);
-        try
-        {
-            FBUtilities.construct(ClassLoadingTestNonAssignable.class.getName(), "test class", Runnable.class);
-            fail("Should not pass");
-        }
-        catch (ConfigurationException e)
-        {
-            assertTrue(e.getMessage().contains("must extend or implement " + Runnable.class.getName()));
-        }
+        assertThatThrownBy(() -> FBUtilities.construct(ClassLoadingTestNonAssignable.class.getName(), "test class", Runnable.class))
+        .isInstanceOf(ConfigurationException.class)
+        .hasMessageContaining("must extend or implement " + Runnable.class.getName());
 
         assertFalse(ClassLoadingTestSupport.wasInitialized(ClassLoadingTestNonAssignable.class));
     }
@@ -94,15 +82,9 @@ public class FBUtilitiesTest
     public void testTypedInstanceOrConstructRejectsWithoutInitializing()
     {
         ClassLoadingTestSupport.assertNotInitialized(ClassLoadingTestNonAssignable.class);
-        try
-        {
-            FBUtilities.instanceOrConstruct(ClassLoadingTestNonAssignable.class.getName(), "test class", Runnable.class);
-            fail("Should not pass");
-        }
-        catch (ConfigurationException e)
-        {
-            assertTrue(e.getMessage().contains("must extend or implement " + Runnable.class.getName()));
-        }
+        assertThatThrownBy(() -> FBUtilities.instanceOrConstruct(ClassLoadingTestNonAssignable.class.getName(), "test class", Runnable.class))
+        .isInstanceOf(ConfigurationException.class)
+        .hasMessageContaining("must extend or implement " + Runnable.class.getName());
 
         assertFalse(ClassLoadingTestSupport.wasInitialized(ClassLoadingTestNonAssignable.class));
     }
@@ -111,17 +93,10 @@ public class FBUtilitiesTest
     public void testNewAuditLoggerRejectsWrongTypeWithoutInitializing()
     {
         ClassLoadingTestSupport.assertNotInitialized(ClassLoadingTestNonAssignable.class);
-        try
-        {
-            FBUtilities.newAuditLogger(ClassLoadingTestNonAssignable.class.getName(), Collections.emptyMap());
-            fail("Should not pass");
-        }
-        catch (ConfigurationException e)
-        {
-            Throwable cause = e.getCause();
-            assertTrue(cause instanceof ConfigurationException);
-            assertTrue(cause.getMessage().contains("must extend or implement " + IAuditLogger.class.getName()));
-        }
+        assertThatThrownBy(() -> FBUtilities.newAuditLogger(ClassLoadingTestNonAssignable.class.getName(), Collections.emptyMap()))
+        .isInstanceOf(ConfigurationException.class)
+        .hasRootCauseInstanceOf(ConfigurationException.class)
+        .hasStackTraceContaining("must extend or implement " + IAuditLogger.class.getName());
 
         assertFalse(ClassLoadingTestSupport.wasInitialized(ClassLoadingTestNonAssignable.class));
     }