diff --git a/grails-core/src/main/groovy/org/grails/compiler/injection/GlobalGrailsClassInjectorTransformation.groovy b/grails-core/src/main/groovy/org/grails/compiler/injection/GlobalGrailsClassInjectorTransformation.groovy
index b1de05aee3e..cbba99b1308 100644
--- a/grails-core/src/main/groovy/org/grails/compiler/injection/GlobalGrailsClassInjectorTransformation.groovy
+++ b/grails-core/src/main/groovy/org/grails/compiler/injection/GlobalGrailsClassInjectorTransformation.groovy
@@ -165,14 +165,14 @@ class GlobalGrailsClassInjectorTransformation implements ASTTransformation, Comp
             if(Modifier.isAbstract(classNode.getModifiers())) return false
 
             def classNodeName = classNode.name
-            // generate META-INF/grails.factories
-            def factoriesFile = new File(compilationTargetDirectory, "META-INF/grails.factories")
-            factoriesFile.parentFile.mkdirs()
+
+            File sourceDirectory = findSourceDirectory(compilationTargetDirectory)
+            def sourceFactoriesFile = new File(sourceDirectory, "src/main/resources/META-INF/grails.factories")
             def props = new Properties()
             def superTypeName = superType.getName()
-            if (factoriesFile.exists()) {
+            if (sourceFactoriesFile.exists()) {
                 // update
-                factoriesFile.withInputStream { InputStream input ->
+                sourceFactoriesFile.withInputStream { InputStream input ->
                     props.load(input)
                 }
 
@@ -186,6 +186,9 @@ class GlobalGrailsClassInjectorTransformation implements ASTTransformation, Comp
             } else {
                 props.put(superTypeName, classNodeName)
             }
+            // generate META-INF/grails.factories
+            def factoriesFile = new File(compilationTargetDirectory, "META-INF/grails.factories")
+            factoriesFile.parentFile.mkdirs()
             factoriesFile.withWriter {  Writer writer ->
                 props.store(writer, "Grails Factories File")
             }
@@ -194,6 +197,14 @@ class GlobalGrailsClassInjectorTransformation implements ASTTransformation, Comp
         return false
     }
 
+    private static File findSourceDirectory(File compilationTargetDirectory) {
+        File sourceDirectory = compilationTargetDirectory
+        while (sourceDirectory != null && !(sourceDirectory.name in ["build", "target"])) {
+            sourceDirectory = sourceDirectory.parentFile
+        }
+        sourceDirectory.parentFile
+    }
+
     static Set<String> pendingPluginClasses = []
     static Collection<String> pluginExcludes = []
 
diff --git a/grails-test-suite-persistence/src/test/groovy/org/grails/orm/support/TransactionManagerPostProcessorTests.groovy b/grails-test-suite-persistence/src/test/groovy/org/grails/orm/support/TransactionManagerPostProcessorTests.groovy
index a42ecdf143a..c1d4d6de8c4 100644
--- a/grails-test-suite-persistence/src/test/groovy/org/grails/orm/support/TransactionManagerPostProcessorTests.groovy
+++ b/grails-test-suite-persistence/src/test/groovy/org/grails/orm/support/TransactionManagerPostProcessorTests.groovy
@@ -3,16 +3,20 @@ package org.grails.orm.support
 import grails.spring.BeanBuilder
 import grails.transaction.TransactionManagerAware
 import org.grails.transaction.TransactionManagerPostProcessor
+import org.junit.jupiter.api.Test
 import org.springframework.jdbc.datasource.DataSourceTransactionManager
 import org.springframework.jdbc.datasource.DriverManagerDataSource
 import org.springframework.transaction.PlatformTransactionManager
 
+import static org.junit.jupiter.api.Assertions.assertNotNull
+
 /**
  * @author Graeme Rocher
  * @since 1.0
  */
-class TransactionManagerPostProcessorTests extends GroovyTestCase{
+class TransactionManagerPostProcessorTests {
 
+    @Test
     void testTransactionManagerPostProccessor() {
         def bb = new BeanBuilder()
 
@@ -35,8 +39,8 @@ class TransactionManagerPostProcessorTests extends GroovyTestCase{
         def ctx = bb.createApplicationContext()
 
         MyBean bean = ctx.getBean("myBean")
-        assert bean
-        assert bean.tm
+        assertNotNull bean
+        assertNotNull bean.tm
     }
 }
 
diff --git a/grails-test-suite-uber/src/test/groovy/grails/util/ClosureToMapPopulatorTests.groovy b/grails-test-suite-uber/src/test/groovy/grails/util/ClosureToMapPopulatorTests.groovy
index 488683d5a51..6bedfd2abec 100644
--- a/grails-test-suite-uber/src/test/groovy/grails/util/ClosureToMapPopulatorTests.groovy
+++ b/grails-test-suite-uber/src/test/groovy/grails/util/ClosureToMapPopulatorTests.groovy
@@ -1,11 +1,16 @@
 package grails.util
 
+import org.junit.jupiter.api.Test
+
+import static org.junit.jupiter.api.Assertions.assertEquals
+
 /**
  * @author Graeme Rocher
  * @since 1.1
  */
-class ClosureToMapPopulatorTests extends GroovyTestCase {
+class ClosureToMapPopulatorTests {
 
+    @Test
     void testPopulate() {
         def populator = new ClosureToMapPopulator()
 
@@ -17,6 +22,6 @@ class ClosureToMapPopulatorTests extends GroovyTestCase {
 
         assertEquals "bar", result.foo
         assertEquals "two", result.one
-        assertEquals "should have returned a list", ["four", "five"], result.three
+        assertEquals(["four", "five"], result.three, "should have returned a list")
     }
 }
diff --git a/grails-test-suite-uber/src/test/groovy/grails/util/CollectionUtilsTests.groovy b/grails-test-suite-uber/src/test/groovy/grails/util/CollectionUtilsTests.groovy
index e0ef959e3ef..ea06812f4e5 100644
--- a/grails-test-suite-uber/src/test/groovy/grails/util/CollectionUtilsTests.groovy
+++ b/grails-test-suite-uber/src/test/groovy/grails/util/CollectionUtilsTests.groovy
@@ -15,8 +15,13 @@
  */
 package grails.util
 
-class CollectionUtilsTests extends GroovyTestCase {
+import org.junit.jupiter.api.Test
 
+import static org.junit.jupiter.api.Assertions.*
+
+class CollectionUtilsTests {
+
+    @Test
     void testNewMapEvenArgs() {
         def map = CollectionUtils.newMap("foo", 1, "bar", 2, "baz", 42)
         assertNotNull map
@@ -26,24 +31,28 @@ class CollectionUtilsTests extends GroovyTestCase {
         assertEquals 42, map.baz
     }
 
+    @Test
     void testNewMapOddArgs() {
-        shouldFail(IllegalArgumentException) {
+        assertThrows(IllegalArgumentException) {
             CollectionUtils.newMap "foo", 1, "bar"
         }
     }
 
+    @Test
     void testNewMapNull() {
         def map = CollectionUtils.newMap(null)
         assertTrue map instanceof Map
         assertEquals 0, map.size()
     }
 
+    @Test
     void testNewSetNull() {
         def set = CollectionUtils.newSet(null)
         assertTrue set instanceof Set
         assertEquals 0, set.size()
     }
 
+    @Test
     void testNewSet() {
         def set = CollectionUtils.newSet(1, 2, 42)
         assertTrue set instanceof Set
@@ -53,12 +62,14 @@ class CollectionUtilsTests extends GroovyTestCase {
         assertTrue set.contains(42)
     }
 
+    @Test
     void testNewListNull() {
         def list = CollectionUtils.newList(null)
         assertTrue list instanceof List
         assertEquals 0, list.size()
     }
 
+    @Test
     void testNewList() {
         def list = CollectionUtils.newList(1, 2, 42)
         assertTrue list instanceof List
diff --git a/grails-test-suite-uber/src/test/groovy/grails/web/JSONBuilderTests.groovy b/grails-test-suite-uber/src/test/groovy/grails/web/JSONBuilderTests.groovy
index cc49bf4c024..f7dde788ff5 100644
--- a/grails-test-suite-uber/src/test/groovy/grails/web/JSONBuilderTests.groovy
+++ b/grails-test-suite-uber/src/test/groovy/grails/web/JSONBuilderTests.groovy
@@ -1,19 +1,25 @@
 package grails.web
 
-import org.grails.web.converters.configuration.ConvertersConfigurationInitializer
 import grails.core.DefaultGrailsApplication
+import org.grails.web.converters.configuration.ConvertersConfigurationInitializer
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+
+import static org.junit.jupiter.api.Assertions.assertEquals
 
 /**
  * @author Graeme Rocher
  * @since 1.2
  */
-class JSONBuilderTests extends GroovyTestCase {
+class JSONBuilderTests {
 
+    @BeforeEach
     void setUp() {
         def initializer = new ConvertersConfigurationInitializer(grailsApplication: new DefaultGrailsApplication())
         initializer.initialize()
     }
-    
+
+    @Test
     void testSimple() {
         def builder = new JSONBuilder()
 
@@ -24,6 +30,7 @@ class JSONBuilderTests extends GroovyTestCase {
         assertEquals '{"rootprop":"something"}', result.toString()
     }
 
+    @Test
     void testArrays() {
         def builder = new JSONBuilder()
 
@@ -35,6 +42,7 @@ class JSONBuilderTests extends GroovyTestCase {
         assertEquals '{"categories":["a","b","c"],"rootprop":"something"}', result.toString()
     }
 
+    @Test
     void testSubObjects() {
         def builder = new JSONBuilder()
 
@@ -49,6 +57,7 @@ class JSONBuilderTests extends GroovyTestCase {
         assertEquals '{"categories":["a","b","c"],"rootprop":"something","test":{"subprop":10}}', result.toString()
     }
 
+    @Test
     void testAssignedObjects() {
 
         def builder = new JSONBuilder()
@@ -64,6 +73,7 @@ class JSONBuilderTests extends GroovyTestCase {
         assertEquals '{"categories":["a","b","c"],"rootprop":"something","test":{"subprop":10}}', result.toString()
     }
 
+    @Test
     void testNamedArgumentHandling() {
         def builder = new JSONBuilder()
 
@@ -76,6 +86,7 @@ class JSONBuilderTests extends GroovyTestCase {
         assertEquals '{"categories":["a","b","c"],"rootprop":"something","test":{"subprop":10,"three":[1,2,3]}}', result.toString()
     }
 
+    @Test
     void testArrayOfClosures() {
         def builder = new JSONBuilder()
 
@@ -86,6 +97,7 @@ class JSONBuilderTests extends GroovyTestCase {
         assertEquals '{"foo":[{"bar":"hello"}]}', result.toString()
     }
 
+    @Test
     void testRootElementList() {
         def builder = new JSONBuilder()
 
@@ -106,6 +118,7 @@ class JSONBuilderTests extends GroovyTestCase {
         assertEquals '["one","two","three"]', result.toString()
     }
 
+    @Test
     void testExampleFromReferenceGuide() {
         def builder = new JSONBuilder()
 
@@ -138,6 +151,7 @@ class JSONBuilderTests extends GroovyTestCase {
         assertEquals '{"books":[{"title":"one"},{"title":"two"},{"title":"three"}]}', result.toString()
     }
 
+    @Test
     void testAppendToArray() {
         def builder = new JSONBuilder()
 
diff --git a/grails-test-suite-uber/src/test/groovy/org/grails/cli/ScriptNameResolverTests.groovy b/grails-test-suite-uber/src/test/groovy/org/grails/cli/ScriptNameResolverTests.groovy
index 225ec390ce9..08e595fdf98 100644
--- a/grails-test-suite-uber/src/test/groovy/org/grails/cli/ScriptNameResolverTests.groovy
+++ b/grails-test-suite-uber/src/test/groovy/org/grails/cli/ScriptNameResolverTests.groovy
@@ -1,20 +1,25 @@
 package org.grails.cli
 
-import org.grails.build.parsing.ScriptNameResolver;
+import org.grails.build.parsing.ScriptNameResolver
+import org.junit.jupiter.api.Test
 
-class ScriptNameResolverTests extends GroovyTestCase {
+import static org.junit.jupiter.api.Assertions.assertTrue
+
+class ScriptNameResolverTests {
+
+    @Test
     void testFoo() {
-        assert ScriptNameResolver.resolvesTo('F', 'Foo')
-        assert ScriptNameResolver.resolvesTo('FB', 'FooBar')
-        assert ScriptNameResolver.resolvesTo('FoB', 'FooBar')
-        assert ScriptNameResolver.resolvesTo('FBa', 'FooBar')
-        assert ScriptNameResolver.resolvesTo('FoBa', 'FooBar')
-        assert ScriptNameResolver.resolvesTo('FooBar', 'FooBar')
-        assert !ScriptNameResolver.resolvesTo('FB', 'FooBarZoo')
-        assert !ScriptNameResolver.resolvesTo('FBaz', 'FooBar')
-        assert !ScriptNameResolver.resolvesTo('FBr', 'FooBar')
-        assert !ScriptNameResolver.resolvesTo('F', 'FooBar')
-        assert !ScriptNameResolver.resolvesTo('Fo', 'FooBar')
-        assert !ScriptNameResolver.resolvesTo('Foo', 'FooBar')
+        assertTrue ScriptNameResolver.resolvesTo('F', 'Foo')
+        assertTrue ScriptNameResolver.resolvesTo('FB', 'FooBar')
+        assertTrue ScriptNameResolver.resolvesTo('FoB', 'FooBar')
+        assertTrue ScriptNameResolver.resolvesTo('FBa', 'FooBar')
+        assertTrue ScriptNameResolver.resolvesTo('FoBa', 'FooBar')
+        assertTrue ScriptNameResolver.resolvesTo('FooBar', 'FooBar')
+        assertTrue !ScriptNameResolver.resolvesTo('FB', 'FooBarZoo')
+        assertTrue !ScriptNameResolver.resolvesTo('FBaz', 'FooBar')
+        assertTrue !ScriptNameResolver.resolvesTo('FBr', 'FooBar')
+        assertTrue !ScriptNameResolver.resolvesTo('F', 'FooBar')
+        assertTrue !ScriptNameResolver.resolvesTo('Fo', 'FooBar')
+        assertTrue !ScriptNameResolver.resolvesTo('Foo', 'FooBar')
     }
 }
diff --git a/grails-test-suite-uber/src/test/groovy/org/grails/commons/DefaultArtefactInfoTests.groovy b/grails-test-suite-uber/src/test/groovy/org/grails/commons/DefaultArtefactInfoTests.groovy
index 388c978f952..c1b9563ffe7 100644
--- a/grails-test-suite-uber/src/test/groovy/org/grails/commons/DefaultArtefactInfoTests.groovy
+++ b/grails-test-suite-uber/src/test/groovy/org/grails/commons/DefaultArtefactInfoTests.groovy
@@ -2,13 +2,17 @@ package org.grails.commons
 
 import grails.core.DefaultArtefactInfo
 import org.grails.core.DefaultGrailsControllerClass
+import org.junit.jupiter.api.Test
+
+import static org.junit.jupiter.api.Assertions.assertEquals
 
 /**
  * @author Graeme Rocher
  * @since 1.0
  */
-class DefaultArtefactInfoTests extends GroovyTestCase {
+class DefaultArtefactInfoTests {
 
+    @Test
     void testAddGrailsClass() {
         def info = new DefaultArtefactInfo()
 
diff --git a/grails-test-suite-uber/src/test/groovy/org/grails/commons/DefaultGrailsCodecClassTests.groovy b/grails-test-suite-uber/src/test/groovy/org/grails/commons/DefaultGrailsCodecClassTests.groovy
index 70389c1cc8c..676bc49e7ea 100644
--- a/grails-test-suite-uber/src/test/groovy/org/grails/commons/DefaultGrailsCodecClassTests.groovy
+++ b/grails-test-suite-uber/src/test/groovy/org/grails/commons/DefaultGrailsCodecClassTests.groovy
@@ -1,18 +1,28 @@
 package org.grails.commons
+
+import org.junit.jupiter.api.AfterEach
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+
+import static org.junit.jupiter.api.Assertions.assertEquals
+
 /**
  * @author Graeme Rocher
  * @since 1.1
  */
-class DefaultGrailsCodecClassTests extends GroovyTestCase {
+class DefaultGrailsCodecClassTests {
 
+    @BeforeEach
     protected void setUp() {
         ExpandoMetaClass.enableGlobally()
     }
 
+    @AfterEach
     protected void tearDown() {
         ExpandoMetaClass.disableGlobally()
     }
 
+    @Test
     void testCodecWithClosures() {
         def codecClass = new DefaultGrailsCodecClass(CodecWithClosuresCodec)
         codecClass.afterPropertiesSet();
@@ -20,6 +30,7 @@ class DefaultGrailsCodecClassTests extends GroovyTestCase {
         assertEquals "decoded", codecClass.decoder.decode("stuff")
     }
 
+    @Test
     void testCodecWithMethods() {
         def codecClass = new DefaultGrailsCodecClass(CodecWithMethodsCodec)
         codecClass.afterPropertiesSet();
diff --git a/grails-test-suite-uber/src/test/groovy/org/grails/commons/GrailsMetaClassUtilsTests.groovy b/grails-test-suite-uber/src/test/groovy/org/grails/commons/GrailsMetaClassUtilsTests.groovy
index a4a50714d59..91b976d39ee 100644
--- a/grails-test-suite-uber/src/test/groovy/org/grails/commons/GrailsMetaClassUtilsTests.groovy
+++ b/grails-test-suite-uber/src/test/groovy/org/grails/commons/GrailsMetaClassUtilsTests.groovy
@@ -1,26 +1,32 @@
 package org.grails.commons
 
 import grails.util.GrailsMetaClassUtils
+import org.junit.jupiter.api.Test
 import org.springframework.beans.BeanUtils
 
+import static org.junit.jupiter.api.Assertions.assertEquals
+import static org.junit.jupiter.api.Assertions.assertNotNull
+
 /**
  * Tests for the GrailsMetaClassUtils class.
  *
  * @author Graeme Rocher
  */
-class GrailsMetaClassUtilsTests extends GroovyTestCase {
+class GrailsMetaClassUtilsTests {
 
+    @Test
     void testGetMetaRegistry() {
         assertNotNull(GrailsMetaClassUtils.getRegistry())
     }
 
+    @Test
     void testCopyExpandoMetaClass() {
         def metaClass = new ExpandoMetaClass(Dummy, true)
 
         // add property
         metaClass.getFoo = {-> "bar" }
         // add instance method
-        metaClass.foo = { String txt -> "bar:$txt" }
+        metaClass.foo = { String txt -> "bar:$txt".toString() }
         // add static method
         metaClass.'static'.bar = {-> "foo" }
         // add constructor
diff --git a/grails-test-suite-uber/src/test/groovy/org/grails/commons/MultipleClassesPerFileTests.groovy b/grails-test-suite-uber/src/test/groovy/org/grails/commons/MultipleClassesPerFileTests.groovy
index 9110d62c7f0..75cbddc59d2 100644
--- a/grails-test-suite-uber/src/test/groovy/org/grails/commons/MultipleClassesPerFileTests.groovy
+++ b/grails-test-suite-uber/src/test/groovy/org/grails/commons/MultipleClassesPerFileTests.groovy
@@ -15,18 +15,24 @@
  */
 package org.grails.commons
 
+import org.junit.jupiter.api.Test
+
+import static org.junit.jupiter.api.Assertions.assertNotNull
+import static org.junit.jupiter.api.Assertions.assertThrows
+
 /**
  * @author Steven Devijver
  */
-class MultipleClassesPerFileTests extends GroovyTestCase {
+class MultipleClassesPerFileTests {
 
+    @Test
     void testMultipleClassesPerFile() {
         GroovyClassLoader cl = new GroovyClassLoader()
         cl.parseClass(getClass().classLoader.getResourceAsStream('org/grails/commons/classes.groovy'), 'classes.groovy')
         assertNotNull cl.loadClass('TestClass1')
         assertNotNull cl.loadClass('TestClass2')
 
-        shouldFail(ClassNotFoundException) {
+        assertThrows(ClassNotFoundException) {
             cl.loadClass('TestClass3')
         }
     }
diff --git a/grails-test-suite-uber/src/test/groovy/org/grails/commons/UrlMappingsArtefactHandlerTests.groovy b/grails-test-suite-uber/src/test/groovy/org/grails/commons/UrlMappingsArtefactHandlerTests.groovy
index 48f31f64aee..555df600f1f 100644
--- a/grails-test-suite-uber/src/test/groovy/org/grails/commons/UrlMappingsArtefactHandlerTests.groovy
+++ b/grails-test-suite-uber/src/test/groovy/org/grails/commons/UrlMappingsArtefactHandlerTests.groovy
@@ -1,15 +1,19 @@
 package org.grails.commons
 
 import org.grails.core.artefact.UrlMappingsArtefactHandler
+import org.junit.jupiter.api.Test
 import org.springframework.core.io.ByteArrayResource
 
+import static org.junit.jupiter.api.Assertions.assertNotNull
+import static org.junit.jupiter.api.Assertions.assertTrue
+
 /**
  * Tests for UrlMappingsArtefactHandler.
  *
  * @author Graeme Rocher
  * @since 0.5
  */
-class UrlMappingsArtefactHandlerTests extends GroovyTestCase {
+class UrlMappingsArtefactHandlerTests {
 
     def mappingScript = '''
 mappings {
@@ -29,12 +33,13 @@ mappings {
 }
 '''
 
+    @Test
     void testUrlMappingsArtefactHandler() {
         def gcl = new GroovyClassLoader()
         Class mappings = gcl.parseClass(new ByteArrayResource(mappingScript.bytes).inputStream, "MyUrlMappings")
         def handler = new UrlMappingsArtefactHandler()
 
-        assert handler.isArtefactClass(mappings)
-        assert handler.newArtefactClass(mappings)
+        assertTrue handler.isArtefactClass(mappings)
+        assertNotNull handler.newArtefactClass(mappings)
     }
 }
diff --git a/grails-test-suite-uber/src/test/groovy/org/grails/commons/metaclass/LazyMetaPropertyMapTests.groovy b/grails-test-suite-uber/src/test/groovy/org/grails/commons/metaclass/LazyMetaPropertyMapTests.groovy
index 7bf9f606647..b226745f2fc 100644
--- a/grails-test-suite-uber/src/test/groovy/org/grails/commons/metaclass/LazyMetaPropertyMapTests.groovy
+++ b/grails-test-suite-uber/src/test/groovy/org/grails/commons/metaclass/LazyMetaPropertyMapTests.groovy
@@ -1,12 +1,16 @@
 package org.grails.commons.metaclass
 
 import grails.beans.util.LazyMetaPropertyMap
+import org.junit.jupiter.api.Test
+
+import static org.junit.jupiter.api.Assertions.*
 
 /**
  * @author Graeme Rocher
  */
-class LazyMetaPropertyMapTests extends GroovyTestCase {
+class LazyMetaPropertyMapTests {
 
+    @Test
     void testOverridePropertiesRecursionBug() {
         PropertyMapTest.metaClass.getProperties = {-> new LazyMetaPropertyMap(delegate) }
 
@@ -16,26 +20,30 @@ class LazyMetaPropertyMapTests extends GroovyTestCase {
         assertEquals 3, obj.properties.size()
     }
 
+    @Test
     void testSelectSubMap() {
 
         def map = new LazyMetaPropertyMap(new PropertyMapTest(name:"Bart", age:11, other:"stuff"))
 
         def submap = map['name', 'age']
-        assertEquals 2, submap.size()
+        assertEquals 2, (int) submap.size()
         assertEquals "Bart", submap.name
-        assertEquals 11, submap.age
+        assertEquals 11, (int) submap.age
     }
 
+    @Test
     void testSize() {
         def map = new LazyMetaPropertyMap(new PropertyMapTest())
         assertEquals 3, map.size()
     }
 
+    @Test
     void testIsEmpty() {
         def map = new LazyMetaPropertyMap(new PropertyMapTest())
         assertFalse map.isEmpty()
     }
 
+    @Test
     void testContainsKey() {
         def map = new LazyMetaPropertyMap(new PropertyMapTest())
 
@@ -44,6 +52,7 @@ class LazyMetaPropertyMapTests extends GroovyTestCase {
         assertFalse map.containsKey("fo")
     }
 
+    @Test
     void testContainsValue() {
         def map = new LazyMetaPropertyMap(new PropertyMapTest(name:"Homer", age:45))
 
@@ -52,6 +61,7 @@ class LazyMetaPropertyMapTests extends GroovyTestCase {
         assertFalse map.containsValue("fo")
     }
 
+    @Test
     void testGet() {
         def map = new LazyMetaPropertyMap(new PropertyMapTest(name:"Homer", age:45))
 
@@ -60,7 +70,7 @@ class LazyMetaPropertyMapTests extends GroovyTestCase {
         assertEquals "Homer", map['name']
 
         assertEquals 45, map.get("age")
-        assertEquals 45, map.age
+        assertEquals 45, (int) map.age
         assertEquals 45, map['age']
 
         assertNull map.foo
@@ -68,6 +78,7 @@ class LazyMetaPropertyMapTests extends GroovyTestCase {
         assertNull map.get('foo')
     }
 
+    @Test
     void testPut() {
         def map = new LazyMetaPropertyMap(new PropertyMapTest(name:"Bart", age:11))
 
@@ -83,6 +94,7 @@ class LazyMetaPropertyMapTests extends GroovyTestCase {
         assertEquals "lisa", map.name
     }
 
+    @Test
     void testKeySet() {
         def map = new LazyMetaPropertyMap(new PropertyMapTest(name:"Bart", age:11))
 
@@ -92,6 +104,7 @@ class LazyMetaPropertyMapTests extends GroovyTestCase {
         assertTrue keys.contains("age")
     }
 
+    @Test
     void testValues() {
         def map = new LazyMetaPropertyMap(new PropertyMapTest(name:"Bart", age:11))
 
diff --git a/grails-test-suite-uber/src/test/groovy/org/grails/plugins/PluginLoadOrderTests.groovy b/grails-test-suite-uber/src/test/groovy/org/grails/plugins/PluginLoadOrderTests.groovy
index 6a2b82ed4d2..ca2e8d7453a 100644
--- a/grails-test-suite-uber/src/test/groovy/org/grails/plugins/PluginLoadOrderTests.groovy
+++ b/grails-test-suite-uber/src/test/groovy/org/grails/plugins/PluginLoadOrderTests.groovy
@@ -2,13 +2,17 @@ package org.grails.plugins
 
 import grails.core.DefaultGrailsApplication
 import grails.plugins.DefaultGrailsPluginManager
+import org.junit.jupiter.api.Test
+
+import static org.junit.jupiter.api.Assertions.assertEquals
 
 /**
  * @author Graeme Rocher
  * @since 1.1
  */
-class PluginLoadOrderTests extends GroovyTestCase {
+class PluginLoadOrderTests {
 
+    @Test
     void testPluginLoadBeforeAfter() {
         def gcl = new GroovyClassLoader()
 
diff --git a/grails-test-suite-uber/src/test/groovy/org/grails/plugins/metadata/GrailsPluginMetadataTests.groovy b/grails-test-suite-uber/src/test/groovy/org/grails/plugins/metadata/GrailsPluginMetadataTests.groovy
index 47f8209d792..0d8737f218e 100644
--- a/grails-test-suite-uber/src/test/groovy/org/grails/plugins/metadata/GrailsPluginMetadataTests.groovy
+++ b/grails-test-suite-uber/src/test/groovy/org/grails/plugins/metadata/GrailsPluginMetadataTests.groovy
@@ -1,16 +1,21 @@
 package org.grails.plugins.metadata
 
-import grails.plugins.DefaultGrailsPluginManager
 import grails.core.DefaultGrailsApplication
+import grails.plugins.DefaultGrailsPluginManager
 import grails.plugins.metadata.GrailsPlugin
 import grails.util.GrailsUtil
+import org.junit.Test
+
+import static org.junit.jupiter.api.Assertions.assertEquals
+import static org.junit.jupiter.api.Assertions.assertNull
 
 /**
  * @author Graeme Rocher
  * @since 1.2
  */
-class GrailsPluginMetadataTests extends GroovyTestCase {
+class GrailsPluginMetadataTests {
 
+    @Test
     void testAnnotatedMetadata() {
         def app = new DefaultGrailsApplication([Test1, Test2, Test3] as Class[], getClass().classLoader)
         def pluginManager = new DefaultGrailsPluginManager([] as Class[], app)
diff --git a/grails-test-suite-uber/src/test/groovy/org/grails/plugins/testing/GrailsMockHttpServletRequestTests.groovy b/grails-test-suite-uber/src/test/groovy/org/grails/plugins/testing/GrailsMockHttpServletRequestTests.groovy
index 3464cfba028..f33d788bb9d 100644
--- a/grails-test-suite-uber/src/test/groovy/org/grails/plugins/testing/GrailsMockHttpServletRequestTests.groovy
+++ b/grails-test-suite-uber/src/test/groovy/org/grails/plugins/testing/GrailsMockHttpServletRequestTests.groovy
@@ -15,11 +15,14 @@
 package org.grails.plugins.testing
 
 import org.grails.plugins.testing.GrailsMockHttpServletRequest
+import org.junit.jupiter.api.Test
+
+import static org.junit.jupiter.api.Assertions.*
 
 /**
  * Test case for {@link org.grails.plugins.testing.GrailsMockHttpServletRequest}.
  */
-class GrailsMockHttpServletRequestTests extends GroovyTestCase {
+class GrailsMockHttpServletRequestTests {
     static final String TEST_XML_CONTENT = """\
 <root>
   <item qty="10">
@@ -43,6 +46,7 @@ class GrailsMockHttpServletRequestTests extends GroovyTestCase {
  { qty: 2, name: "Chair", type: "Furniture" } ]
 """
 
+    @Test
     void testGetXML() {
         // Set up the test data.
         def request = new GrailsMockHttpServletRequest()
@@ -54,6 +58,7 @@ class GrailsMockHttpServletRequestTests extends GroovyTestCase {
         verifyXmlResult request.XML
     }
 
+    @Test
     void testGetXMLMultipleCalls() {
         def request = new GrailsMockHttpServletRequest()
         request.method = 'POST'
@@ -70,14 +75,16 @@ class GrailsMockHttpServletRequestTests extends GroovyTestCase {
         verifyXmlResult request.XML
     }
 
+    @Test
     void testGetXMLNoContent() {
         def request = new GrailsMockHttpServletRequest()
         request.method = 'POST'
-        shouldFail {
+        assertThrows(Exception) {
             request.XML
         }
     }
 
+    @Test
     void testGetXMLContentNotXml() {
         // Set up the test data.
         def content = """\
@@ -90,11 +97,12 @@ Second line
         request.content = content.getBytes("UTF-8")
 
         // Test the method.
-        shouldFail {
+        assertThrows(Exception) {
             request.XML
         }
     }
 
+    @Test
     void testGetJSON() {
         // Set up the test data.
         def request = new GrailsMockHttpServletRequest()
@@ -105,6 +113,7 @@ Second line
         verifyJsonResult request.JSON
     }
 
+    @Test
     void testGetJSONMultipleCalls() {
         // Set up the test data.
         def request = new GrailsMockHttpServletRequest()
@@ -121,11 +130,13 @@ Second line
         verifyJsonResult request.JSON
     }
 
+    @Test
     void testGetJSONNoContent() {
         def request = new GrailsMockHttpServletRequest()
-        assert request.JSON.size() == 0
+        assertEquals 0, (Integer) request.JSON.size()
     }
 
+    @Test
     void testGetJSONContentNotJson() {
         // Set up the test data.
         def content = """\
@@ -137,18 +148,18 @@ Second line
         request.content = content.getBytes("UTF-8")
 
         // Test the method.
-        assert !request.JSON : "should not contain JSON"
+        assertTrue request.JSON.isEmpty(), "should not contain JSON"
     }
 
     private void verifyXmlResult(xml) {
-        assertEquals 3, xml.item.size()
-        assertEquals "Apple", xml.item[1].name.text()
-        assertEquals "2", xml.item[2].@qty.text()
+        assertEquals 3, (int) xml.item.size()
+        assertEquals "Apple", (String) xml.item[1].name.text()
+        assertEquals "2", (String) xml.item[2].@qty.text()
     }
 
     private void verifyJsonResult(json) {
-        assertEquals 3, json.size()
-        assertEquals "Apple", json[1].name
-        assertEquals 2, json[2].qty
+        assertEquals 3, (int) json.size()
+        assertEquals "Apple", (String) json[1].name
+        assertEquals 2, (int) json[2].qty
     }
 }
diff --git a/grails-test-suite-uber/src/test/groovy/org/grails/plugins/testing/GrailsMockHttpServletResponseTests.groovy b/grails-test-suite-uber/src/test/groovy/org/grails/plugins/testing/GrailsMockHttpServletResponseTests.groovy
index 1ee0df75cf2..3b6d69aa27d 100644
--- a/grails-test-suite-uber/src/test/groovy/org/grails/plugins/testing/GrailsMockHttpServletResponseTests.groovy
+++ b/grails-test-suite-uber/src/test/groovy/org/grails/plugins/testing/GrailsMockHttpServletResponseTests.groovy
@@ -15,15 +15,19 @@
 package org.grails.plugins.testing
 
 import org.grails.plugins.testing.GrailsMockHttpServletResponse
+import org.junit.jupiter.api.Test
+
+import static org.junit.jupiter.api.Assertions.assertEquals
 
 /**
  * Test case for {@link org.grails.plugins.testing.GrailsMockHttpServletResponse}.
  */
-class GrailsMockHttpServletResponseTests extends GroovyTestCase {
+class GrailsMockHttpServletResponseTests {
     /**
      * Tests that the left-shift operator appends the given text to the
      * response output.
      */
+    @Test
     void testLeftShift() {
         def testResponse = new GrailsMockHttpServletResponse()
         assertEquals "", testResponse.contentAsString
diff --git a/grails-test-suite-uber/src/test/groovy/org/grails/plugins/testing/GrailsMockHttpSessionTests.groovy b/grails-test-suite-uber/src/test/groovy/org/grails/plugins/testing/GrailsMockHttpSessionTests.groovy
index 623bd0f5729..286ae60f999 100644
--- a/grails-test-suite-uber/src/test/groovy/org/grails/plugins/testing/GrailsMockHttpSessionTests.groovy
+++ b/grails-test-suite-uber/src/test/groovy/org/grails/plugins/testing/GrailsMockHttpSessionTests.groovy
@@ -15,11 +15,15 @@
 package org.grails.plugins.testing
 
 import org.grails.plugins.testing.GrailsMockHttpSession
+import org.junit.jupiter.api.Test
+
+import static org.junit.jupiter.api.Assertions.assertEquals
+import static org.junit.jupiter.api.Assertions.assertNull
 
 /**
  * Test case for {@link org.grails.plugins.testing.GrailsMockHttpSession}.
  */
-class GrailsMockHttpSessionTests extends GroovyTestCase {
+class GrailsMockHttpSessionTests {
     /**
      * Tests that property access on the session retrieves the value
      * for the attribute with the same name as the property unless
@@ -27,6 +31,7 @@ class GrailsMockHttpSessionTests extends GroovyTestCase {
      * the session should only retrieve an attribute if the property
      * is missing.
      */
+    @Test
     void testGetProperty() {
         // Set up the test session with some attributes.
         def testSession = new GrailsMockHttpSession()
@@ -52,6 +57,7 @@ class GrailsMockHttpSessionTests extends GroovyTestCase {
      * notation, while real properties on the session can still be
      * modified.
      */
+    @Test
     void testSetProperty() {
         // Set up the test session.
         def testSession = new GrailsMockHttpSession()
@@ -75,6 +81,7 @@ class GrailsMockHttpSessionTests extends GroovyTestCase {
      * the session should only retrieve an attribute if the property
      * is missing.
      */
+    @Test
     void testGetAt() {
         // Set up the test session with some attributes.
         def testSession = new GrailsMockHttpSession()
@@ -96,6 +103,7 @@ class GrailsMockHttpSessionTests extends GroovyTestCase {
      * notation, while real properties on the session can still be
      * modified.
      */
+    @Test
     void testPutAt() {
         // Set up the test session.
         def testSession = new GrailsMockHttpSession()
diff --git a/grails-test-suite-uber/src/test/groovy/org/grails/reload/SpringProxiedBeanReloadTests.groovy b/grails-test-suite-uber/src/test/groovy/org/grails/reload/SpringProxiedBeanReloadTests.groovy
index f439f18e6d5..a1bb23647fa 100644
--- a/grails-test-suite-uber/src/test/groovy/org/grails/reload/SpringProxiedBeanReloadTests.groovy
+++ b/grails-test-suite-uber/src/test/groovy/org/grails/reload/SpringProxiedBeanReloadTests.groovy
@@ -1,18 +1,22 @@
 package org.grails.reload
 
 import grails.spring.BeanBuilder
-import org.junit.Ignore
-import org.springframework.aop.framework.ProxyFactoryBean
 import org.aopalliance.intercept.MethodInterceptor
 import org.aopalliance.intercept.MethodInvocation
+import org.junit.Ignore
+import org.junit.jupiter.api.Test
+import org.springframework.aop.framework.ProxyFactoryBean
+
+import static org.junit.jupiter.api.Assertions.assertEquals
 
 /**
  * @author Graeme Rocher
  * @since 1.0
  */
 @Ignore //TODO Ignore for JDK 11
-class SpringProxiedBeanReloadTests extends GroovyTestCase {
+class SpringProxiedBeanReloadTests {
 
+    @Test
     void testReloadCGLibProxiedBean() {
         def gcl = new GroovyClassLoader()
         def cls = gcl.parseClass("class Book { String title = 'The Stand'; String author }")
diff --git a/grails-test-suite-uber/src/test/groovy/org/grails/test/support/ControllerNameExtractorTests.groovy b/grails-test-suite-uber/src/test/groovy/org/grails/test/support/ControllerNameExtractorTests.groovy
index 18de588626f..c087b4ec375 100644
--- a/grails-test-suite-uber/src/test/groovy/org/grails/test/support/ControllerNameExtractorTests.groovy
+++ b/grails-test-suite-uber/src/test/groovy/org/grails/test/support/ControllerNameExtractorTests.groovy
@@ -1,9 +1,13 @@
 package org.grails.test.support
 
 import org.grails.test.support.ControllerNameExtractor
+import org.junit.jupiter.api.Test
 
-class ControllerNameExtractorTests extends GroovyTestCase {
+import static org.junit.jupiter.api.Assertions.assertEquals
 
+class ControllerNameExtractorTests {
+
+    @Test
     void testExtractControllerNameFromTestClassName() {
 
         String[] testClassSuffixes = ['Test', 'Tests']
diff --git a/grails-test-suite-uber/src/test/groovy/org/grails/web/errors/GrailsExceptionResolverTests.groovy b/grails-test-suite-uber/src/test/groovy/org/grails/web/errors/GrailsExceptionResolverTests.groovy
index bbc970c4a8d..aa73015c878 100644
--- a/grails-test-suite-uber/src/test/groovy/org/grails/web/errors/GrailsExceptionResolverTests.groovy
+++ b/grails-test-suite-uber/src/test/groovy/org/grails/web/errors/GrailsExceptionResolverTests.groovy
@@ -14,6 +14,9 @@ import org.grails.support.MockApplicationContext
 import org.grails.web.mapping.DefaultUrlMappingEvaluator
 import org.grails.web.mapping.DefaultUrlMappingsHolder
 import org.grails.web.servlet.view.CompositeViewResolver
+import org.junit.jupiter.api.AfterEach
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
 import org.springframework.mock.web.MockHttpServletRequest
 import org.springframework.mock.web.MockHttpServletResponse
 import org.springframework.mock.web.MockServletContext
@@ -23,30 +26,33 @@ import org.springframework.web.multipart.support.StandardServletMultipartResolve
 import org.springframework.web.servlet.View
 import org.springframework.web.servlet.ViewResolver
 import org.springframework.web.servlet.view.InternalResourceView
+
+import static org.junit.jupiter.api.Assertions.*
+
 /**
  * Test case for {@link org.grails.web.errors.GrailsExceptionResolver}.
  */
-class GrailsExceptionResolverTests extends GroovyTestCase {
+class GrailsExceptionResolverTests {
 
     private application = new DefaultGrailsApplication()
     private resolver = new GrailsExceptionResolver()
     private mockContext = new MockServletContext()
     private mockCtx = new MockApplicationContext()
 
-    @Override
-    protected void tearDown() {
+    @AfterEach
+    void tearDown() {
         RequestContextHolder.resetRequestAttributes()
     }
 
-    @Override
-    protected void setUp() throws Exception {
+    @BeforeEach
+    void setUp() throws Exception {
         mockCtx.registerMockBean(GrailsApplication.APPLICATION_ID, new DefaultGrailsApplication())
-        super.setUp();
         def mainContext = new MockApplicationContext();
         mainContext.registerMockBean(UrlConverter.BEAN_NAME, new CamelCaseUrlConverter());
         application.mainContext =  mainContext
     }
 
+    @Test
     void testGetRootCause() {
         def ex = new Exception()
         assertEquals ex, GrailsExceptionResolver.getRootCause(ex)
@@ -58,11 +64,12 @@ class GrailsExceptionResolverTests extends GroovyTestCase {
         ex = new IllegalStateException(ex)
         assertEquals root, GrailsExceptionResolver.getRootCause(ex)
 
-        shouldFail(NullPointerException) {
+        assertThrows(NullPointerException) {
             GrailsExceptionResolver.getRootCause(null)
         }
     }
 
+    @Test
     void testResolveExceptionToView() {
         def mappings = new DefaultUrlMappingEvaluator(mockCtx).evaluateMappings {
             "500"(view:"myView")
@@ -89,10 +96,11 @@ class GrailsExceptionResolverTests extends GroovyTestCase {
         def handler = new Object()
         def modelAndView = resolver.resolveException(request, response, handler, ex)
 
-        assertNotNull "should have returned a ModelAndView", modelAndView
+        assertNotNull modelAndView, "should have returned a ModelAndView"
         assertEquals "/myView", modelAndView.view.url
     }
 
+    @Test
     void testResolveExceptionToController() {
         def mappings = new DefaultUrlMappingEvaluator(mockCtx).evaluateMappings {
             "500"(controller:"foo", action:"bar")
@@ -117,12 +125,13 @@ class GrailsExceptionResolverTests extends GroovyTestCase {
         def handler = new Object()
         def modelAndView = resolver.resolveException(request, response, handler, ex)
 
-        assertNotNull "should have returned a ModelAndView", modelAndView
+        assertNotNull modelAndView, "should have returned a ModelAndView"
         assertTrue modelAndView.empty
 
         assertEquals "/foo/bar",response.getForwardedUrl()
     }
 
+    @Test
     void testResolveExceptionToControllerWhenResponseCommitted() {
         def mappings = new DefaultUrlMappingEvaluator(mockCtx).evaluateMappings {
             "500"(controller:"foo", action:"bar")
@@ -148,10 +157,11 @@ class GrailsExceptionResolverTests extends GroovyTestCase {
         response.setCommitted(true)
         def modelAndView = resolver.resolveException(request, response, handler, ex)
 
-        assertNotNull "should have returned a ModelAndView", modelAndView
+        assertNotNull modelAndView, "should have returned a ModelAndView"
         assertFalse modelAndView.empty
     }
 
+    @Test
     void testLogRequestWithException() {
         def config = new ConfigSlurper().parse('''
 grails.exceptionresolver.params.exclude = ['jennysPhoneNumber']
@@ -175,6 +185,7 @@ bad things happened. Stacktrace follows:'''.replaceAll('[\n\r]', ''), msg.replac
 
     }
 
+    @Test
     void testLogRequest() {
         def config = new ConfigSlurper().parse('''
 grails.exceptionresolver.params.exclude = ['jennysPhoneNumber']
@@ -197,6 +208,7 @@ jennysPhoneNumber: ***
 Stacktrace follows:'''.replaceAll('[\n\r]', ''), msg.replaceAll('[\n\r]', '')
     }
 
+    @Test
     void testDisablingRequestParameterLogging() {
 
         def oldEnvName = Environment.current.name
diff --git a/grails-test-suite-uber/src/test/groovy/org/grails/web/filters/HiddenHttpMethodFilterTests.groovy b/grails-test-suite-uber/src/test/groovy/org/grails/web/filters/HiddenHttpMethodFilterTests.groovy
index accbf0126a5..cbb5b13d572 100644
--- a/grails-test-suite-uber/src/test/groovy/org/grails/web/filters/HiddenHttpMethodFilterTests.groovy
+++ b/grails-test-suite-uber/src/test/groovy/org/grails/web/filters/HiddenHttpMethodFilterTests.groovy
@@ -1,16 +1,21 @@
 package org.grails.web.filters
 
 import org.grails.web.filters.HiddenHttpMethodFilter
+import org.junit.jupiter.api.Test
 import org.springframework.mock.web.MockHttpServletRequest
 import org.springframework.mock.web.MockHttpServletResponse
+
 import javax.servlet.FilterChain
 
+import static org.junit.jupiter.api.Assertions.assertEquals
+
 /**
  * @author Graeme Rocher
  * @since 1.1
  */
-class HiddenHttpMethodFilterTests extends GroovyTestCase {
+class HiddenHttpMethodFilterTests {
 
+    @Test
     void testDefaultCase() {
         def filter = new HiddenHttpMethodFilter()
         def req = new MockHttpServletRequest()
@@ -22,6 +27,7 @@ class HiddenHttpMethodFilterTests extends GroovyTestCase {
         assertEquals "POST", method
     }
 
+    @Test
     void testWithParameter() {
         def filter = new HiddenHttpMethodFilter()
         def req = new MockHttpServletRequest()
@@ -34,6 +40,7 @@ class HiddenHttpMethodFilterTests extends GroovyTestCase {
         assertEquals "DELETE", method
     }
 
+    @Test
     void testWithHeader() {
         def filter = new HiddenHttpMethodFilter()
         def req = new MockHttpServletRequest()
diff --git a/grails-test-suite-uber/src/test/groovy/org/grails/web/i18n/ParamsAwareLocaleChangeInterceptorTests.groovy b/grails-test-suite-uber/src/test/groovy/org/grails/web/i18n/ParamsAwareLocaleChangeInterceptorTests.groovy
index 249f9491b4c..6d2df3e3092 100644
--- a/grails-test-suite-uber/src/test/groovy/org/grails/web/i18n/ParamsAwareLocaleChangeInterceptorTests.groovy
+++ b/grails-test-suite-uber/src/test/groovy/org/grails/web/i18n/ParamsAwareLocaleChangeInterceptorTests.groovy
@@ -1,22 +1,28 @@
 package org.grails.web.i18n
 
 import grails.util.GrailsWebMockUtil
-
+import org.junit.jupiter.api.AfterEach
+import org.junit.jupiter.api.Test
 import org.springframework.mock.web.MockHttpServletRequest
 import org.springframework.web.context.request.RequestContextHolder
 import org.springframework.web.servlet.DispatcherServlet
 import org.springframework.web.servlet.i18n.SessionLocaleResolver
 
+import static org.junit.jupiter.api.Assertions.assertEquals
+import static org.junit.jupiter.api.Assertions.assertNotEquals
+
 /**
  * @author Graeme Rocher
  * @since 1.0
  */
-class ParamsAwareLocaleChangeInterceptorTests extends GroovyTestCase {
+class ParamsAwareLocaleChangeInterceptorTests {
 
+    @AfterEach
     protected void tearDown() {
         RequestContextHolder.resetRequestAttributes()
     }
 
+    @Test
     void testSwitchLocaleWithStringArrayParamsObject() {
 
         def webRequest = GrailsWebMockUtil.bindMockWebRequest()
@@ -40,7 +46,7 @@ class ParamsAwareLocaleChangeInterceptorTests extends GroovyTestCase {
 
         assert localeChangeInterceptor.preHandle(request, response, null)
 
-        assertNotSame locale, localeResolver.resolveLocale(request)
+        assertNotEquals locale, localeResolver.resolveLocale(request)
 
         locale = localeResolver.resolveLocale(request)
 
@@ -48,6 +54,7 @@ class ParamsAwareLocaleChangeInterceptorTests extends GroovyTestCase {
         assertEquals "DE", locale.getCountry()
     }
 
+    @Test
     void testSwitchLocaleWithParamsObject() {
 
         def webRequest = GrailsWebMockUtil.bindMockWebRequest()
@@ -71,7 +78,7 @@ class ParamsAwareLocaleChangeInterceptorTests extends GroovyTestCase {
 
         assert localeChangeInterceptor.preHandle(request, response, null)
 
-        assertNotSame locale, localeResolver.resolveLocale(request)
+        assertNotEquals locale, localeResolver.resolveLocale(request)
 
         locale = localeResolver.resolveLocale(request)
 
@@ -79,7 +86,8 @@ class ParamsAwareLocaleChangeInterceptorTests extends GroovyTestCase {
         assertEquals "DE", locale.getCountry()
     }
 
-    void testSwithLocaleWithRequestParameter() {
+    @Test
+    void testSwitchLocaleWithRequestParameter() {
 
         def webRequest = GrailsWebMockUtil.bindMockWebRequest()
 
@@ -102,7 +110,7 @@ class ParamsAwareLocaleChangeInterceptorTests extends GroovyTestCase {
 
         assert localeChangeInterceptor.preHandle(request, response, null)
 
-        assertNotSame locale, localeResolver.resolveLocale(request)
+        assertNotEquals locale, localeResolver.resolveLocale(request)
 
         locale = localeResolver.resolveLocale(request)
 
diff --git a/grails-test-suite-uber/src/test/groovy/org/grails/web/json/JSONObjectTests.groovy b/grails-test-suite-uber/src/test/groovy/org/grails/web/json/JSONObjectTests.groovy
index 93bd552b0aa..25a3f910740 100644
--- a/grails-test-suite-uber/src/test/groovy/org/grails/web/json/JSONObjectTests.groovy
+++ b/grails-test-suite-uber/src/test/groovy/org/grails/web/json/JSONObjectTests.groovy
@@ -1,13 +1,15 @@
 package org.grails.web.json
 
+import org.junit.jupiter.api.Test
 import spock.lang.Issue
 
 /**
  * @author Graeme Rocher
  * @since 1.0
  */
-class JSONObjectTests extends GroovyTestCase {
+class JSONObjectTests {
 
+    @Test
     void testContainsKey() {
         JSONObject j = new JSONObject()
         j.put('test', 1)
diff --git a/grails-test-suite-uber/src/test/groovy/org/grails/web/metaclass/WithFormMethodTests.groovy b/grails-test-suite-uber/src/test/groovy/org/grails/web/metaclass/WithFormMethodTests.groovy
index 7158b4b40be..c8d72255a97 100644
--- a/grails-test-suite-uber/src/test/groovy/org/grails/web/metaclass/WithFormMethodTests.groovy
+++ b/grails-test-suite-uber/src/test/groovy/org/grails/web/metaclass/WithFormMethodTests.groovy
@@ -17,34 +17,38 @@ package org.grails.web.metaclass
 
 import grails.artefact.Controller
 import grails.util.GrailsWebMockUtil
-
 import org.grails.core.exceptions.GrailsRuntimeException
 import org.grails.web.servlet.mvc.SynchronizerTokensHolder
+import org.junit.jupiter.api.AfterEach
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
 import org.springframework.web.context.request.RequestContextHolder
 
+import static org.junit.jupiter.api.Assertions.*
+
 /**
  * @author Graeme Rocher
  * @since 1.1
  */
-class WithFormMethodTests extends GroovyTestCase {
+class WithFormMethodTests {
 
     private withForm = new WithFormMethod()
     private request
 
-    @Override
-    protected void setUp() {
-        super.setUp()
+    @BeforeEach
+    void setUp() {
         request = GrailsWebMockUtil.bindMockWebRequest()
     }
 
-    @Override
-    protected void tearDown() {
+    @AfterEach
+    void tearDown() {
         RequestContextHolder.resetRequestAttributes()
     }
 
+    @Test
     void testMissingToken() {
 
-        shouldFail(GrailsRuntimeException) {
+        assertThrows(GrailsRuntimeException) {
             withForm.withForm(request) {
                 // should not get here
             }.invalidToken {
@@ -53,11 +57,12 @@ class WithFormMethodTests extends GroovyTestCase {
         }
     }
 
+    @Test
     void testTokenHolderEmpty() {
 
         request.session.setAttribute(SynchronizerTokensHolder.HOLDER,new SynchronizerTokensHolder())
 
-        shouldFail(GrailsRuntimeException) {
+        assertThrows(GrailsRuntimeException) {
             withForm.withForm(request) {
                 // should not get here
             }.invalidToken {
@@ -66,6 +71,7 @@ class WithFormMethodTests extends GroovyTestCase {
         }
     }
 
+    @Test
     void testTokenInvalidWithEmptyTokenHolder() {
         def url = "http://grails.org/submit"
 
@@ -74,7 +80,7 @@ class WithFormMethodTests extends GroovyTestCase {
         request.currentRequest.addParameter(SynchronizerTokensHolder.TOKEN_URI,url)
         request.currentRequest.addParameter(SynchronizerTokensHolder.TOKEN_KEY,UUID.randomUUID().toString())
 
-        shouldFail(GrailsRuntimeException) {
+        assertThrows(GrailsRuntimeException) {
             withForm.withForm(request) {
                 // should not get here
             }.invalidToken {
@@ -83,8 +89,9 @@ class WithFormMethodTests extends GroovyTestCase {
         }
     }
 
+    @Test
     void testTokenInvalid() {
-        def url = "http://grails.org/submit"
+        def url = "https://grails.org/submit"
 
         SynchronizerTokensHolder tokensHolder = new SynchronizerTokensHolder()
         tokensHolder.generateToken(url)
@@ -93,7 +100,7 @@ class WithFormMethodTests extends GroovyTestCase {
         request.currentRequest.addParameter(SynchronizerTokensHolder.TOKEN_URI,url)
         request.currentRequest.addParameter(SynchronizerTokensHolder.TOKEN_KEY,UUID.randomUUID().toString())
 
-        shouldFail(GrailsRuntimeException) {
+        assertThrows(GrailsRuntimeException) {
             withForm.withForm(request) {
                 // should not get here
             }.invalidToken {
@@ -102,6 +109,7 @@ class WithFormMethodTests extends GroovyTestCase {
         }
     }
 
+    @Test
     void testTokenValid() {
         def url = "http://grails.org/submit"
 
@@ -121,6 +129,7 @@ class WithFormMethodTests extends GroovyTestCase {
         assertEquals "bar", result.foo
     }
 
+    @Test
     void testNonEmptyHolderStays() {
         def url1 = "http://grails.org/submit1"
         def url2 = "http://grails.org/submit2"
@@ -145,6 +154,7 @@ class WithFormMethodTests extends GroovyTestCase {
         assertTrue tokensHolder.isValid(url2, token2)
     }
 
+    @Test
     void testEmptyHolderIsDeleted() {
         def url = "http://grails.org/submit"
 
@@ -164,8 +174,9 @@ class WithFormMethodTests extends GroovyTestCase {
         assertNull request.session.getAttribute(SynchronizerTokensHolder.HOLDER)
     }
 
+    @Test
     void testHandleDoubleSubmit() {
-        def url = "http://grails.org/submit"
+        def url = "https://grails.org/submit"
 
         SynchronizerTokensHolder tokensHolder = new SynchronizerTokensHolder()
         def token = tokensHolder.generateToken(url)
@@ -182,7 +193,7 @@ class WithFormMethodTests extends GroovyTestCase {
 
         assertEquals "bar", result.foo
 
-        shouldFail(GrailsRuntimeException) {
+        assertThrows(GrailsRuntimeException) {
             withForm.withForm(request) {
                 // should not get here
             }.invalidToken {
@@ -191,9 +202,10 @@ class WithFormMethodTests extends GroovyTestCase {
         }
     }
 
+    @Test
     void testHandleSubmitOfTwoForms() {
-        def url1 = "http://grails.org/submit1"
-        def url2 = "http://grails.org/submit2"
+        def url1 = "https://grails.org/submit1"
+        def url2 = "https://grails.org/submit2"
 
         SynchronizerTokensHolder tokensHolder = new SynchronizerTokensHolder()
         def token1 = tokensHolder.generateToken(url1)
@@ -225,9 +237,10 @@ class WithFormMethodTests extends GroovyTestCase {
         assertEquals "bar", result2.foo
     }
 
+    @Test
     void testHandleSubmitOfTwoFormsWithSameURL() {
-        def url1 = "http://grails.org/submit"
-        def url2 = "http://grails.org/submit"
+        def url1 = "https://grails.org/submit"
+        def url2 = "https://grails.org/submit"
 
         SynchronizerTokensHolder tokensHolder = new SynchronizerTokensHolder()
         def token1 = tokensHolder.generateToken(url1)
@@ -258,7 +271,7 @@ class WithFormMethodTests extends GroovyTestCase {
 
         assertEquals "bar", result2.foo
 
-        shouldFail(GrailsRuntimeException) {
+        assertThrows(GrailsRuntimeException) {
             withForm.withForm(request2) {
                 return [foo:"bar"]
             }.invalidToken {
@@ -268,4 +281,4 @@ class WithFormMethodTests extends GroovyTestCase {
     }
 }
 
-class WithFormMethod implements Controller {}
\ No newline at end of file
+class WithFormMethod implements Controller {}
diff --git a/grails-test-suite-uber/src/test/groovy/org/grails/web/util/WebUtilsTests.groovy b/grails-test-suite-uber/src/test/groovy/org/grails/web/util/WebUtilsTests.groovy
index 01543747b9c..66695be4d40 100644
--- a/grails-test-suite-uber/src/test/groovy/org/grails/web/util/WebUtilsTests.groovy
+++ b/grails-test-suite-uber/src/test/groovy/org/grails/web/util/WebUtilsTests.groovy
@@ -2,24 +2,31 @@ package org.grails.web.util
 
 import grails.core.DefaultGrailsApplication
 import grails.core.GrailsApplication
+import grails.web.mime.MimeType
 import org.grails.config.PropertySourcesConfig
 import org.grails.plugins.web.mime.MimeTypesFactoryBean
 import org.grails.support.MockApplicationContext
-import grails.web.mime.MimeType
 import org.grails.web.servlet.mvc.GrailsWebRequest
+import org.junit.jupiter.api.AfterEach
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
 import org.springframework.mock.web.MockHttpServletRequest
 import org.springframework.mock.web.MockHttpServletResponse
 import org.springframework.mock.web.MockServletContext
 import org.springframework.web.context.request.RequestContextHolder
 
+import static org.junit.jupiter.api.Assertions.*
+
 /**
  * @author Graeme Rocher
  * @since 1.0
  */
-class WebUtilsTests extends GroovyTestCase {
+class WebUtilsTests {
 
     def config
-    protected void setUp() {
+
+    @BeforeEach
+    void setUp() {
         RequestContextHolder.resetRequestAttributes()
         config = new ConfigSlurper().parse("""
 grails.mime.file.extensions=false
@@ -38,15 +45,17 @@ grails.mime.types = [ html: ['text/html','application/xhtml+xml'],
                     ]        """)
     }
 
-    protected void tearDown() {
+    @AfterEach
+    void tearDown() {
         RequestContextHolder.resetRequestAttributes()
     }
 
+    @Test
     void testAreFileExtensionsEnabled() {
         def ga = new DefaultGrailsApplication(config:new PropertySourcesConfig().merge(config))
         bindMockRequest(ga)
 
-        assert !WebUtils.areFileExtensionsEnabled()
+        assertFalse WebUtils.areFileExtensionsEnabled()
 
         config = new ConfigSlurper().parse("""
 grails.mime.file.extensions=true
@@ -54,7 +63,7 @@ grails.mime.file.extensions=true
 
         ga.config = new PropertySourcesConfig().merge(config)
 
-        assert WebUtils.areFileExtensionsEnabled()
+        assertTrue WebUtils.areFileExtensionsEnabled()
     }
 
     private def bindMockRequest(DefaultGrailsApplication ga) {
@@ -70,6 +79,7 @@ grails.mime.file.extensions=true
         RequestContextHolder.setRequestAttributes(webRequest)
     }
 
+    @Test
     void testGetFormatFromURI() {
         def ga = new DefaultGrailsApplication(config:new PropertySourcesConfig().merge(config))
         bindMockRequest(ga)
@@ -84,6 +94,7 @@ grails.mime.file.extensions=true
         assertEquals "xml", WebUtils.getFormatFromURI("/foo/bar.suff/bar.xml")
     }
 
+    @Test
     void testGetRequestURIForGrailsDispatchURI() {
         def request = new MockHttpServletRequest()
         request.contextPath = "/root"
@@ -96,13 +107,14 @@ grails.mime.file.extensions=true
         assertEquals "/example/index",WebUtils.getRequestURIForGrailsDispatchURI(request)
     }
 
+    @Test
     void testRetrieveGrailsWebRequest() {
         // Validate the initial conditions.
         assertNull RequestContextHolder.getRequestAttributes()
 
         // An exception should be thrown if no web request is attached
         // to the thread.
-        shouldFail(IllegalStateException) {
+        assertThrows(IllegalStateException) {
             WebUtils.retrieveGrailsWebRequest()
         }
 
@@ -116,6 +128,7 @@ grails.mime.file.extensions=true
         assertEquals mockWebRequest, WebUtils.retrieveGrailsWebRequest()
     }
 
+    @Test
     void testStoreGrailsWebRequest() {
         // Validate the initial conditions.
         assertNull RequestContextHolder.getRequestAttributes()
@@ -136,6 +149,7 @@ grails.mime.file.extensions=true
         assertEquals mockWebRequest, mockHttpRequest.getAttribute(GrailsApplicationAttributes.WEB_REQUEST)
     }
 
+    @Test
     void clearGrailsWebRequest() {
         // Create a mock web request and store it on the thread.
         def mockHttpRequest = new MockHttpServletRequest()
diff --git a/grails-test-suite-web/src/test/groovy/org/grails/web/servlet/mvc/SynchronizerTokensHolderTests.groovy b/grails-test-suite-web/src/test/groovy/org/grails/web/servlet/mvc/SynchronizerTokensHolderTests.groovy
index 31be5bcd380..610e5a0f628 100644
--- a/grails-test-suite-web/src/test/groovy/org/grails/web/servlet/mvc/SynchronizerTokensHolderTests.groovy
+++ b/grails-test-suite-web/src/test/groovy/org/grails/web/servlet/mvc/SynchronizerTokensHolderTests.groovy
@@ -1,8 +1,12 @@
 package org.grails.web.servlet.mvc
 
+import org.junit.jupiter.api.Test
 
-class SynchronizerTokensHolderTests extends GroovyTestCase {
+import static org.junit.jupiter.api.Assertions.*
 
+class SynchronizerTokensHolderTests {
+
+    @Test
     // GRAILS-9923
     void testSerializable() {
         SynchronizerTokensHolder holder = new SynchronizerTokensHolder()
@@ -17,68 +21,72 @@ class SynchronizerTokensHolderTests extends GroovyTestCase {
 
         ObjectInputStream ios = new ObjectInputStream(new ByteArrayInputStream(data))
         def deserialized = ios.readObject()
-        assert deserialized instanceof SynchronizerTokensHolder
+        assertTrue deserialized instanceof SynchronizerTokensHolder
 
         SynchronizerTokensHolder holder2 = deserialized
-        assert holder2.currentTokens == holder.currentTokens
-        assert 2 == holder2.currentTokens.size()
+        assertEquals holder2.currentTokens, holder.currentTokens
+        assertEquals 2, holder2.currentTokens.size()
 
         holder.generateToken 'url3'
-        assert 2 == holder2.currentTokens.size()
+        assertEquals 2, holder2.currentTokens.size()
 
         holder2.generateToken 'url3'
-        assert 3 == holder2.currentTokens.size()
+        assertEquals 3, holder2.currentTokens.size()
     }
 
+    @Test
     void testGenerate() {
         SynchronizerTokensHolder holder = new SynchronizerTokensHolder()
         assert holder.empty
 
         String url1 = 'url1'
-        assert holder.generateToken(url1)
-        assert 1 == holder.currentTokens.size()
-        assert 1 == holder.currentTokens[url1].size()
+        assertNotNull holder.generateToken(url1)
+        assertEquals 1, holder.currentTokens.size()
+        assertEquals 1, holder.currentTokens[url1].size()
 
-        assert holder.generateToken(url1)
-        assert 1 == holder.currentTokens.size()
-        assert 2 == holder.currentTokens[url1].size()
+        assertNotNull holder.generateToken(url1)
+        assertEquals 1, holder.currentTokens.size()
+        assertEquals 2, holder.currentTokens[url1].size()
 
         String url2 = 'url2'
-        assert holder.generateToken(url2)
-        assert 2 == holder.currentTokens.size()
-        assert 2 == holder.currentTokens[url1].size()
-        assert 1 == holder.currentTokens[url2].size()
+        assertNotNull holder.generateToken(url2)
+        assertEquals 2, holder.currentTokens.size()
+        assertEquals 2, holder.currentTokens[url1].size()
+        assertEquals 1, holder.currentTokens[url2].size()
     }
 
+    @Test
     void testIsValid() {
         SynchronizerTokensHolder holder = new SynchronizerTokensHolder()
-        assert holder.empty
+        assertTrue holder.empty
 
         String url = 'url1'
 
         String token = holder.generateToken(url)
-        assert holder.isValid(url, token)
-        assert !holder.isValid(url, token + '!')
+        assertTrue holder.isValid(url, token)
+        assertFalse holder.isValid(url, token + '!')
     }
 
+    @Test
     void testResetTokens() {
         SynchronizerTokensHolder holder = new SynchronizerTokensHolder()
-        assert holder.empty
+        assertTrue holder.empty
 
         String url1 = 'url1'
         String url2 = 'url2'
 
-        assert holder.generateToken(url1)
-        assert holder.generateToken(url2)
-        assert 2 == holder.currentTokens.size()
+        assertNotNull holder.generateToken(url1)
+        assertNotNull holder.generateToken(url2)
+        assertEquals 2, holder.currentTokens.size()
 
         holder.resetToken url1
-        assert 1 == holder.currentTokens.size()
+        assertEquals 1, holder.currentTokens.size()
 
         holder.resetToken url2
-        assert 0 == holder.currentTokens.size()
+        assertEquals 0, holder.currentTokens.size()
     }
 
+    @Test
     void testResetToken() {
         SynchronizerTokensHolder holder = new SynchronizerTokensHolder()
 
@@ -89,24 +97,24 @@ class SynchronizerTokensHolderTests extends GroovyTestCase {
         String token2 = holder.generateToken(url1)
         String token3 = holder.generateToken(url1)
         String token4 = holder.generateToken(url2)
-        assert 2 == holder.currentTokens.size()
+        assertEquals 2, holder.currentTokens.size()
 
         holder.resetToken url1, token1
-        assert 2 == holder.currentTokens.size()
+        assertEquals 2, holder.currentTokens.size()
 
         holder.resetToken url1, token2
-        assert 2 == holder.currentTokens.size()
+        assertEquals 2, holder.currentTokens.size()
 
         holder.resetToken url1, token3
-        assert 1 == holder.currentTokens.size()
+        assertEquals 1, holder.currentTokens.size()
 
         holder.resetToken url1, token4
-        assert 1 == holder.currentTokens.size()
+        assertEquals 1, holder.currentTokens.size()
 
         holder.resetToken url1, token4 + '!'
-        assert 1 == holder.currentTokens.size()
+        assertEquals 1, holder.currentTokens.size()
 
         holder.resetToken url2, token4
-        assert 0 == holder.currentTokens.size()
+        assertEquals 0, holder.currentTokens.size()
     }
 }
diff --git a/grails-test-suite-web/src/test/groovy/org/grails/web/servlet/view/GroovyPageViewTests.groovy b/grails-test-suite-web/src/test/groovy/org/grails/web/servlet/view/GroovyPageViewTests.groovy
index efb118da15f..51175c8d20d 100644
--- a/grails-test-suite-web/src/test/groovy/org/grails/web/servlet/view/GroovyPageViewTests.groovy
+++ b/grails-test-suite-web/src/test/groovy/org/grails/web/servlet/view/GroovyPageViewTests.groovy
@@ -1,13 +1,19 @@
 package org.grails.web.servlet.view
+
 import grails.util.GrailsWebMockUtil
 import org.grails.core.io.MockStringResourceLoader
 import org.grails.gsp.GroovyPagesTemplateEngine
 import org.grails.support.MockApplicationContext
+import org.junit.jupiter.api.AfterEach
+import org.junit.jupiter.api.Test
 import org.springframework.web.context.request.RequestContextHolder
 
+import static org.junit.jupiter.api.Assertions.assertEquals
+
 @SuppressWarnings("unused")
-class GroovyPageViewTests extends GroovyTestCase {
+class GroovyPageViewTests {
 
+    @Test
     void testGroovyPageView() {
         def webRequest = GrailsWebMockUtil.bindMockWebRequest()
 
@@ -37,6 +43,7 @@ class GroovyPageViewTests extends GroovyTestCase {
         assertEquals "successbar", webRequest.currentResponse.contentAsString
     }
 
+    @AfterEach
     void tearDown() {
          RequestContextHolder.resetRequestAttributes()
     }
diff --git a/grails-web-url-mappings/src/test/groovy/org/grails/web/mapping/DefaultUrlCreatorTests.groovy b/grails-web-url-mappings/src/test/groovy/org/grails/web/mapping/DefaultUrlCreatorTests.groovy
index 2f11fbf408c..661d6128c00 100644
--- a/grails-web-url-mappings/src/test/groovy/org/grails/web/mapping/DefaultUrlCreatorTests.groovy
+++ b/grails-web-url-mappings/src/test/groovy/org/grails/web/mapping/DefaultUrlCreatorTests.groovy
@@ -1,12 +1,16 @@
 package org.grails.web.mapping
 
 import grails.util.GrailsWebMockUtil
-
 import org.grails.web.mapping.DefaultUrlCreator
-import org.springframework.web.context.request.*
+import org.junit.jupiter.api.AfterEach
+import org.junit.jupiter.api.Test
+import org.springframework.web.context.request.RequestContextHolder
+
+import static org.junit.jupiter.api.Assertions.assertEquals
 
-class DefaultUrlCreatorTests extends GroovyTestCase {
+class DefaultUrlCreatorTests {
 
+    @Test
     void testCreateUrl() {
 
         def webRequest = GrailsWebMockUtil.bindMockWebRequest()
@@ -22,6 +26,7 @@ class DefaultUrlCreatorTests extends GroovyTestCase {
         assertEquals "/foo/index?hello=world&fred=flintstone", creator.createURL(hello:"world", fred:"flintstone", "utf-8")
     }
 
+    @Test
     void testCreateUrlNoCharacterEncoding() {
         def webRequest = GrailsWebMockUtil.bindMockWebRequest()
         webRequest.currentRequest.characterEncoding = null
@@ -31,6 +36,7 @@ class DefaultUrlCreatorTests extends GroovyTestCase {
         assertEquals "/foo/index", creator.createURL(null, "utf-8")
     }
 
+    @AfterEach
     void tearDown() {
         RequestContextHolder.resetRequestAttributes()
     }