diff --git a/utbot-core/src/main/kotlin/org/utbot/common/KClassUtil.kt b/utbot-core/src/main/kotlin/org/utbot/common/KClassUtil.kt
index 69b14167f7..92e4d8d398 100644
--- a/utbot-core/src/main/kotlin/org/utbot/common/KClassUtil.kt
+++ b/utbot-core/src/main/kotlin/org/utbot/common/KClassUtil.kt
@@ -8,12 +8,8 @@ import java.lang.reflect.Method
  * NOTE: vararg parameters must be passed as an array of the corresponding type.
  */
 fun Method.invokeCatching(obj: Any?, args: List<Any?>) = try {
-    val invocation =
-        try {
-            invoke(obj, *args.toTypedArray())
-        } catch (e: Throwable) {
-            null
-        }
+    val invocation = invoke(obj, *args.toTypedArray())
+
     Result.success(invocation)
 } catch (e: InvocationTargetException) {
     Result.failure<Nothing>(e.targetException)
diff --git a/utbot-framework-api/src/main/kotlin/org/utbot/framework/UtSettings.kt b/utbot-framework-api/src/main/kotlin/org/utbot/framework/UtSettings.kt
index fbdcaf4642..68267044d3 100644
--- a/utbot-framework-api/src/main/kotlin/org/utbot/framework/UtSettings.kt
+++ b/utbot-framework-api/src/main/kotlin/org/utbot/framework/UtSettings.kt
@@ -240,7 +240,7 @@ object UtSettings : AbstractSettings(logger, defaultKeyForSettingsPath, defaultS
     /**
      * Set to true to start fuzzing if symbolic execution haven't return anything
      */
-    var useFuzzing: Boolean by getBooleanProperty(false)
+    var useFuzzing: Boolean by getBooleanProperty(true)
 
     /**
      * Set to true to use grey-box fuzzing
diff --git a/utbot-framework-api/src/main/kotlin/org/utbot/framework/plugin/api/Api.kt b/utbot-framework-api/src/main/kotlin/org/utbot/framework/plugin/api/Api.kt
index b3799f47ba..1813769347 100644
--- a/utbot-framework-api/src/main/kotlin/org/utbot/framework/plugin/api/Api.kt
+++ b/utbot-framework-api/src/main/kotlin/org/utbot/framework/plugin/api/Api.kt
@@ -480,7 +480,7 @@ data class UtArrayModel(
  * @param instantiationCall is an [UtExecutableCallModel] to instantiate represented object. It **must** not return `null`.
  * @param modificationsChain is a chain of [UtStatementModel] to construct object state.
  */
-data class UtAssembleModel constructor(
+data class UtAssembleModel private constructor(
     override val id: Int?,
     override val classId: ClassId,
     override val modelName: String,
diff --git a/utbot-framework-api/src/main/kotlin/org/utbot/framework/plugin/api/util/UtContext.kt b/utbot-framework-api/src/main/kotlin/org/utbot/framework/plugin/api/util/UtContext.kt
index ad064bfb3a..9152d986c3 100644
--- a/utbot-framework-api/src/main/kotlin/org/utbot/framework/plugin/api/util/UtContext.kt
+++ b/utbot-framework-api/src/main/kotlin/org/utbot/framework/plugin/api/util/UtContext.kt
@@ -5,7 +5,7 @@ import org.utbot.common.currentThreadInfo
 import org.utbot.framework.plugin.api.util.UtContext.Companion.setUtContext
 import kotlin.coroutines.CoroutineContext
 import kotlinx.coroutines.ThreadContextElement
-//import mu.KotlinLogging
+import mu.KotlinLogging
 
 val utContext: UtContext
     get() = UtContext.currentContext()
@@ -75,7 +75,7 @@ inline fun <T> withUtContext(context: UtContext, block: () -> T): T = setUtConte
     try {
         return@use block.invoke()
     } catch (e: Exception) {
-        //KotlinLogging.logger("withUtContext").error { e }
+        KotlinLogging.logger("withUtContext").error { e }
         throw e
     }
 }
diff --git a/utbot-framework-api/src/main/kotlin/org/utbot/framework/plugin/api/util/constructor/ValueConstructor.kt b/utbot-framework-api/src/main/kotlin/org/utbot/framework/plugin/api/util/constructor/ValueConstructor.kt
index f845801f83..962fd54446 100644
--- a/utbot-framework-api/src/main/kotlin/org/utbot/framework/plugin/api/util/constructor/ValueConstructor.kt
+++ b/utbot-framework-api/src/main/kotlin/org/utbot/framework/plugin/api/util/constructor/ValueConstructor.kt
@@ -42,7 +42,6 @@ import org.utbot.framework.plugin.api.util.anyInstance
 import org.utbot.framework.plugin.api.util.constructLambda
 import org.utbot.framework.plugin.api.util.constructStaticLambda
 import org.utbot.framework.plugin.api.util.constructor
-import org.utbot.framework.plugin.api.util.id
 import org.utbot.framework.plugin.api.util.isStatic
 import org.utbot.framework.plugin.api.util.jClass
 import org.utbot.framework.plugin.api.util.jField
diff --git a/utbot-framework/build.gradle b/utbot-framework/build.gradle
index 5d28b5c817..be62217c6d 100644
--- a/utbot-framework/build.gradle
+++ b/utbot-framework/build.gradle
@@ -6,7 +6,6 @@ repositories {
 
 configurations {
     z3native
-    fetchInstrumentationJar
 }
 
 dependencies {
@@ -36,10 +35,6 @@ dependencies {
     implementation group: 'io.github.microutils', name: 'kotlin-logging', version: kotlinLoggingVersion
     implementation group: 'org.jacoco', name: 'org.jacoco.report', version: jacocoVersion
     implementation group: 'org.apache.commons', name: 'commons-text', version: apacheCommonsTextVersion
-    implementation "org.javaruntype:javaruntype:1.3"
-    implementation "ru.vyarus:generics-resolver:3.0.3"
-    implementation "ognl:ognl:3.3.2"
-
     // we need this for construction mocks from composite models
     implementation group: 'org.mockito', name: 'mockito-core', version: '4.2.0'
 
@@ -51,7 +46,6 @@ dependencies {
     z3native group: 'com.microsoft.z3', name: 'z3-native-win64', version: z3Version, ext: 'zip'
     z3native group: 'com.microsoft.z3', name: 'z3-native-linux64', version: z3Version, ext: 'zip'
     z3native group: 'com.microsoft.z3', name: 'z3-native-osx', version: z3Version, ext: 'zip'
-    fetchInstrumentationJar project(path: ':utbot-instrumentation', configuration:'instrumentationArchive')
 }
 
 processResources {
@@ -60,7 +54,4 @@ processResources {
             into "lib/x64"
         }
     }
-    from(configurations.fetchInstrumentationJar) {
-        into "lib"
-    }
 }
diff --git a/utbot-framework/src/main/kotlin/org/utbot/engine/UtBotSymbolicEngine.kt b/utbot-framework/src/main/kotlin/org/utbot/engine/UtBotSymbolicEngine.kt
index cfb1e85682..943dc7401b 100644
--- a/utbot-framework/src/main/kotlin/org/utbot/engine/UtBotSymbolicEngine.kt
+++ b/utbot-framework/src/main/kotlin/org/utbot/engine/UtBotSymbolicEngine.kt
@@ -46,7 +46,6 @@ import org.utbot.fuzzing.utils.Trie
 import org.utbot.greyboxfuzzer.GreyBoxFuzzer
 import org.utbot.greyboxfuzzer.util.FuzzerUtModelConstructor
 import org.utbot.instrumentation.ConcreteExecutor
-import ru.vyarus.java.generics.resolver.context.GenericsInfoFactory
 import org.utbot.instrumentation.instrumentation.execution.UtConcreteExecutionData
 import org.utbot.instrumentation.instrumentation.execution.UtConcreteExecutionResult
 import org.utbot.instrumentation.instrumentation.execution.UtExecutionInstrumentation
diff --git a/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/domain/context/CgContext.kt b/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/domain/context/CgContext.kt
index cc3b736644..356d07270a 100644
--- a/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/domain/context/CgContext.kt
+++ b/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/domain/context/CgContext.kt
@@ -551,9 +551,8 @@ data class CgContext(
         }
     }
 
-    private var nestedClassIndex = 0
     private fun createClassIdForNestedClass(testClassModel: TestClassModel): ClassId {
-        val simpleName = "${testClassModel.classUnderTest.simpleName}Test${nestedClassIndex++}"
+        val simpleName = "${testClassModel.classUnderTest.simpleName}Test"
         return BuiltinClassId(
             canonicalName = currentTestClass.canonicalName + "." + simpleName,
             simpleName = simpleName,
diff --git a/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/domain/models/CgElement.kt b/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/domain/models/CgElement.kt
index b68f751b13..ba98a9fd4c 100644
--- a/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/domain/models/CgElement.kt
+++ b/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/domain/models/CgElement.kt
@@ -134,7 +134,7 @@ class CgClass(
     val body: CgClassBody,
     val isStatic: Boolean,
     val isNested: Boolean,
-): CgStatement {
+): CgElement {
     val packageName
         get() = id.packageName
 
diff --git a/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/renderer/CgAbstractRenderer.kt b/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/renderer/CgAbstractRenderer.kt
index f2dd9f1fff..a2b7056f05 100644
--- a/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/renderer/CgAbstractRenderer.kt
+++ b/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/renderer/CgAbstractRenderer.kt
@@ -623,15 +623,7 @@ abstract class CgAbstractRenderer(
                 is Boolean -> toStringConstant()
                 // String is "\"" + "str" + "\"", RawString is "str"
                 is String -> if (asRawString) "$this".escapeCharacters() else toStringConstant()
-                else -> {
-                    val t = this@toStringConstant.type
-                    val illegalType = t.toString().contains("$") || !t.isPublic
-                    if (this == null && UtSettings.greyBoxFuzzingCompetitionMode && !illegalType) {
-                        "(${this@toStringConstant.type}) null"
-                    } else {
-                        "$this"
-                    }
-                }
+                else -> "$this"
             }
         }
 
diff --git a/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/renderer/CgJavaRenderer.kt b/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/renderer/CgJavaRenderer.kt
index 6493d8df5a..b6371cac60 100644
--- a/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/renderer/CgJavaRenderer.kt
+++ b/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/renderer/CgJavaRenderer.kt
@@ -238,11 +238,6 @@ internal class CgJavaRenderer(context: CgRendererContext, printer: CgPrinter = C
         renderExceptions(element)
     }
 
-    private fun getTypeStringRepresentation(typeId: ClassId): String =
-        when {
-            typeId.isArray -> getTypeStringRepresentation(typeId.elementClassId!!) + "[]"
-            else -> typeId.toString()
-        }
 
     override fun renderMethodSignature(element: CgMockMethod) {
         val returnType = element.returnType.asString()
diff --git a/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/services/framework/MockFrameworkManager.kt b/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/services/framework/MockFrameworkManager.kt
index 59d471a62c..0e8c05a7ce 100644
--- a/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/services/framework/MockFrameworkManager.kt
+++ b/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/services/framework/MockFrameworkManager.kt
@@ -20,30 +20,78 @@ import org.utbot.framework.codegen.domain.builtin.thenReturnMethodId
 import org.utbot.framework.codegen.domain.builtin.whenMethodId
 import org.utbot.framework.codegen.domain.context.CgContext
 import org.utbot.framework.codegen.domain.context.CgContextOwner
-import org.utbot.framework.codegen.domain.models.*
+import org.utbot.framework.codegen.domain.models.CgAnnotation
+import org.utbot.framework.codegen.domain.models.CgAnonymousFunction
+import org.utbot.framework.codegen.domain.models.CgAssignment
+import org.utbot.framework.codegen.domain.models.CgClass
+import org.utbot.framework.codegen.domain.models.CgClassBody
+import org.utbot.framework.codegen.domain.models.CgConstructorCall
+import org.utbot.framework.codegen.domain.models.CgDeclaration
+import org.utbot.framework.codegen.domain.models.CgDocumentationComment
+import org.utbot.framework.codegen.domain.models.CgExecutableCall
+import org.utbot.framework.codegen.domain.models.CgExpression
+import org.utbot.framework.codegen.domain.models.CgLiteral
+import org.utbot.framework.codegen.domain.models.CgMethodCall
+import org.utbot.framework.codegen.domain.models.CgMethodsCluster
+import org.utbot.framework.codegen.domain.models.CgMockMethod
+import org.utbot.framework.codegen.domain.models.CgParameterDeclaration
+import org.utbot.framework.codegen.domain.models.CgRunnable
+import org.utbot.framework.codegen.domain.models.CgSimpleRegion
+import org.utbot.framework.codegen.domain.models.CgStatement
+import org.utbot.framework.codegen.domain.models.CgStatementExecutableCall
+import org.utbot.framework.codegen.domain.models.CgStaticRunnable
+import org.utbot.framework.codegen.domain.models.CgSwitchCase
+import org.utbot.framework.codegen.domain.models.CgSwitchCaseLabel
+import org.utbot.framework.codegen.domain.models.CgValue
+import org.utbot.framework.codegen.domain.models.CgVariable
 import org.utbot.framework.codegen.services.access.CgCallableAccessManager
 import org.utbot.framework.codegen.services.access.CgCallableAccessManagerImpl
 import org.utbot.framework.codegen.tree.*
+import org.utbot.framework.codegen.tree.buildClassBody
+import org.utbot.framework.codegen.tree.CgStatementConstructor
+import org.utbot.framework.codegen.tree.CgVariableConstructor
 import org.utbot.framework.codegen.tree.CgStatementConstructorImpl
 import org.utbot.framework.codegen.tree.CgTestClassConstructor.CgComponents.getVariableConstructorBy
 import org.utbot.framework.codegen.tree.hasAmbiguousOverloadsOf
 import org.utbot.framework.codegen.util.isAccessibleFrom
-import org.utbot.framework.plugin.api.*
-import org.utbot.framework.plugin.api.util.*
-import java.lang.IllegalStateException
+import org.utbot.framework.plugin.api.BuiltinClassId
+import org.utbot.framework.plugin.api.ClassId
+import org.utbot.framework.plugin.api.ConstructorId
+import org.utbot.framework.plugin.api.ExecutableId
+import org.utbot.framework.plugin.api.MethodId
+import org.utbot.framework.plugin.api.TypeParameters
+import org.utbot.framework.plugin.api.UtCompositeModel
+import org.utbot.framework.plugin.api.UtModel
+import org.utbot.framework.plugin.api.UtNewInstanceInstrumentation
+import org.utbot.framework.plugin.api.UtStaticMethodInstrumentation
+import org.utbot.framework.plugin.api.util.atomicIntegerClassId
+import org.utbot.framework.plugin.api.util.atomicIntegerGet
+import org.utbot.framework.plugin.api.util.atomicIntegerGetAndIncrement
+import org.utbot.framework.plugin.api.util.booleanClassId
+import org.utbot.framework.plugin.api.util.byteClassId
+import org.utbot.framework.plugin.api.util.charClassId
+import org.utbot.framework.plugin.api.util.doubleClassId
+import org.utbot.framework.plugin.api.util.floatClassId
+import org.utbot.framework.plugin.api.util.id
+import org.utbot.framework.plugin.api.util.intClassId
+import org.utbot.framework.plugin.api.util.longClassId
+import org.utbot.framework.plugin.api.util.shortClassId
+import org.utbot.framework.plugin.api.util.voidClassId
+import org.utbot.framework.plugin.api.util.isRefType
+import org.utbot.framework.plugin.api.util.exceptions
 
 abstract class CgVariableConstructorComponent(val context: CgContext) :
-    CgContextOwner by context,
-    CgCallableAccessManager by CgCallableAccessManagerImpl(context),
-    CgStatementConstructor by CgStatementConstructorImpl(context) {
+        CgContextOwner by context,
+        CgCallableAccessManager by CgCallableAccessManagerImpl(context),
+        CgStatementConstructor by CgStatementConstructorImpl(context) {
 
     val variableConstructor: CgVariableConstructor by lazy { getVariableConstructorBy(context) }
 
     fun mockitoArgumentMatchersFor(executable: ExecutableId): Array<CgMethodCall> =
-        executable.parameters.map {
-            val matcher = it.mockitoAnyMatcher(executable.classId.hasAmbiguousOverloadsOf(executable))
-            if (matcher != anyOfClass) argumentMatchersClassId[matcher]() else matchByClass(it)
-        }.toTypedArray()
+            executable.parameters.map {
+                val matcher = it.mockitoAnyMatcher(executable.classId.hasAmbiguousOverloadsOf(executable))
+                if (matcher != anyOfClass) argumentMatchersClassId[matcher]() else matchByClass(it)
+            }.toTypedArray()
 
     /**
      * Clears all resources required for [currentExecution].
@@ -63,22 +111,22 @@ abstract class CgVariableConstructorComponent(val context: CgContext) :
     }
 
     fun ClassId.mockitoAnyMatcher(withExplicitClass: Boolean): MethodId =
-        when (this) {
-            byteClassId -> anyByte
-            charClassId -> anyChar
-            shortClassId -> anyShort
-            intClassId -> anyInt
-            longClassId -> anyLong
-            floatClassId -> anyFloat
-            doubleClassId -> anyDouble
-            booleanClassId -> anyBoolean
-            // we cannot match by string here
-            // because anyString accepts only non-nullable strings but argument could be null
-            else -> if (withExplicitClass) anyOfClass else any
-        }
+            when (this) {
+                byteClassId -> anyByte
+                charClassId -> anyChar
+                shortClassId -> anyShort
+                intClassId -> anyInt
+                longClassId -> anyLong
+                floatClassId -> anyFloat
+                doubleClassId -> anyDouble
+                booleanClassId -> anyBoolean
+                // we cannot match by string here
+                // because anyString accepts only non-nullable strings but argument could be null
+                else -> if (withExplicitClass) anyOfClass else any
+            }
 
     private fun matchByClass(id: ClassId): CgMethodCall =
-        argumentMatchersClassId[anyOfClass](getClassOf(id))
+            argumentMatchersClassId[anyOfClass](getClassOf(id))
 }
 
 /**
@@ -127,7 +175,8 @@ private class InPlaceMocker(context: CgContext) : ObjectMocker(context) {
                                     }
                                 }.catch(Throwable::class.id) {
                                     throwStatement {
-                                        val constructor = IllegalStateException::class.java.id.allConstructors.first { it.parameters.isEmpty() }
+                                        val constructor =
+                                            IllegalStateException::class.java.id.allConstructors.first { it.parameters.isEmpty() }
                                         constructor()
                                     }
                                 }
@@ -139,14 +188,14 @@ private class InPlaceMocker(context: CgContext) : ObjectMocker(context) {
                 )
             }
         val methodsCluster = CgSimpleRegion(null, methods)
-        val declaration = buildClass {
+        val classDeclaration = buildClass {
             id = mockClassId
             interfaces.add(model.classId)
             body = buildClassBody(mockClassId) {
                 methodRegions += CgMethodsCluster(header = null, content = listOf(methodsCluster))
             }
         }
-        currentBlock += declaration
+        currentBlock += CgClassAsStatement(classDeclaration)
         ++mockID
         val constructorId = ConstructorId(mockClassId, emptyList())
         return newVar(model.classId, baseName) {
@@ -162,6 +211,34 @@ private class InPlaceMocker(context: CgContext) : ObjectMocker(context) {
         TODO("Not yet implemented")
     }
 
+    private class CgClassAsStatement(
+        val id: ClassId,
+        val documentation: CgDocumentationComment?,
+        val annotations: List<CgAnnotation>,
+        val superclass: ClassId?,
+        val interfaces: List<ClassId>,
+        val body: CgClassBody,
+        val isStatic: Boolean,
+        val isNested: Boolean
+    ) : CgStatement {
+        constructor(cgClass: CgClass) : this(
+            cgClass.id,
+            cgClass.documentation,
+            cgClass.annotations,
+            cgClass.superclass,
+            cgClass.interfaces,
+            cgClass.body,
+            cgClass.isStatic,
+            cgClass.isNested
+        )
+
+        val packageName
+            get() = id.packageName
+
+        val simpleName
+            get() = id.simpleName
+    }
+
 }
 
 class MockFrameworkManager(context: CgContext) : CgVariableConstructorComponent(context) {
@@ -200,7 +277,7 @@ class MockFrameworkManager(context: CgContext) : CgVariableConstructorComponent(
 }
 
 private abstract class ObjectMocker(
-    context: CgContext
+        context: CgContext
 ) : CgVariableConstructorComponent(context) {
     abstract fun createMock(model: UtCompositeModel, baseName: String): CgVariable
 
@@ -210,7 +287,7 @@ private abstract class ObjectMocker(
 }
 
 private abstract class StaticMocker(
-    context: CgContext
+        context: CgContext
 ) : CgVariableConstructorComponent(context) {
     abstract fun mockNewInstance(mock: UtNewInstanceInstrumentation)
     abstract fun mockStaticMethodsOfClass(classId: ClassId, methodMocks: List<UtStaticMethodInstrumentation>)
@@ -232,7 +309,7 @@ private class MockitoMocker(context: CgContext) : ObjectMocker(context) {
             when (executable) {
                 is MethodId -> {
                     if (executable.parameters.any { !it.isAccessibleFrom(testClassPackageName) }) {
-                        error("Cannot mock method $executable with not accessible parameters")
+                        error("Cannot mock method $executable with not accessible parameters" )
                     }
 
                     val matchers = mockitoArgumentMatchersFor(executable)
@@ -243,7 +320,6 @@ private class MockitoMocker(context: CgContext) : ObjectMocker(context) {
                     val results = values.map { variableConstructor.getOrCreateVariable(it) }.toTypedArray()
                     `when`(mockObject[executable](*matchers)).thenReturn(executable.returnType, *results)
                 }
-
                 else -> error("ConstructorId was not expected to appear in simple mocker but got $executable")
             }
         }
@@ -252,10 +328,10 @@ private class MockitoMocker(context: CgContext) : ObjectMocker(context) {
     }
 
     override fun mock(clazz: CgExpression): CgMethodCall =
-        mockitoClassId[mockMethodId](clazz)
+            mockitoClassId[mockMethodId](clazz)
 
     override fun `when`(call: CgExecutableCall): CgMethodCall =
-        mockitoClassId[whenMethodId](call)
+            mockitoClassId[whenMethodId](call)
 }
 
 private class MockitoStaticMocker(context: CgContext, private val mocker: ObjectMocker) : StaticMocker(context) {
@@ -301,7 +377,7 @@ private class MockitoStaticMocker(context: CgContext, private val mocker: Object
     override fun mockStaticMethodsOfClass(classId: ClassId, methodMocks: List<UtStaticMethodInstrumentation>) {
         for ((methodId, values) in methodMocks) {
             if (methodId.parameters.any { !it.isAccessibleFrom(testClassPackageName) }) {
-                error("Cannot mock static method $methodId with not accessible parameters")
+                error("Cannot mock static method $methodId with not accessible parameters" )
             }
 
             val matchers = mockitoArgumentMatchersFor(methodId)
@@ -316,10 +392,10 @@ private class MockitoStaticMocker(context: CgContext, private val mocker: Object
                     listOf(
                         CgStatementExecutableCall(
                             CgMethodCall(
-                                caller = null,
-                                methodId,
-                                matchers.toList()
-                            )
+                        caller = null,
+                        methodId,
+                        matchers.toList()
+                    )
                         )
                     )
                 )
@@ -389,7 +465,6 @@ private class MockitoStaticMocker(context: CgContext, private val mocker: Object
                             mocker.`when`(mockParameter[executable](*matchers))[thenReturnMethodId](*results)
                         )
                     }
-
                     else -> error("Expected MethodId but got ConstructorId $executable")
                 }
             }
diff --git a/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/tree/Builders.kt b/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/tree/Builders.kt
index ce858d1c93..90b5d0b54e 100644
--- a/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/tree/Builders.kt
+++ b/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/tree/Builders.kt
@@ -85,7 +85,7 @@ interface CgMethodBuilder<T : CgMethod> : CgBuilder<T> {
 
 class CgTestMethodBuilder : CgMethodBuilder<CgTestMethod> {
     override lateinit var name: String
-    override var returnType: ClassId = voidClassId
+    override val returnType: ClassId = voidClassId
     override lateinit var parameters: List<CgParameterDeclaration>
     override lateinit var statements: List<CgStatement>
     override val exceptions: MutableSet<ClassId> = mutableSetOf()
diff --git a/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/tree/CgMethodConstructor.kt b/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/tree/CgMethodConstructor.kt
index 09d978248a..8d98e8bcd5 100644
--- a/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/tree/CgMethodConstructor.kt
+++ b/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/tree/CgMethodConstructor.kt
@@ -5,7 +5,6 @@ import org.utbot.common.WorkaroundReason
 import org.utbot.common.isStatic
 import org.utbot.common.workaround
 import org.utbot.engine.ArtificialError
-import org.utbot.engine.OverflowDetectionError
 import org.utbot.greyboxfuzzer.util.UtGreyBoxFuzzedExecution
 import org.utbot.framework.assemble.assemble
 import org.utbot.framework.codegen.domain.ForceStaticMocking
@@ -134,7 +133,6 @@ import java.lang.reflect.InvocationTargetException
 import java.security.AccessControlException
 import java.lang.reflect.ParameterizedType
 import org.utbot.framework.UtSettings
-import org.utbot.framework.codegen.domain.models.*
 import org.utbot.framework.codegen.services.access.CgCallableAccessManager
 import org.utbot.framework.codegen.services.access.CgFieldStateManagerImpl
 import org.utbot.framework.codegen.services.framework.TestFrameworkManager
diff --git a/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/tree/CgVariableConstructor.kt b/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/tree/CgVariableConstructor.kt
index 7c6d8f4b05..cf5d44ed9d 100644
--- a/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/tree/CgVariableConstructor.kt
+++ b/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/tree/CgVariableConstructor.kt
@@ -197,18 +197,22 @@ open class CgVariableConstructor(val context: CgContext) :
                 is UtDirectSetFieldModel -> {
                     val instance = declareOrGet(statementModel.instance)
                     // fields here are supposed to be accessible, so we assign them directly without any checks
-                    val fieldValue = declareOrGet(statementModel.fieldModel)
-                    if (statementModel.fieldId.canBeSetFrom(context) && fieldValue.type isSubtypeOf statementModel.fieldId.type) {
-                        instance[statementModel.fieldId] `=` fieldValue
-                    } else {
-                        with(statementModel) {
-                            +utilsClassId[setField](
-                                instance,
-                                fieldId.declaringClass.name,
-                                fieldId.name,
-                                fieldValue
-                            )
+                    if (UtSettings.useGreyBoxFuzzing) {
+                        val fieldValue = declareOrGet(statementModel.fieldModel)
+                        if (statementModel.fieldId.canBeSetFrom(context) && fieldValue.type isSubtypeOf statementModel.fieldId.type) {
+                            instance[statementModel.fieldId] `=` fieldValue
+                        } else {
+                            with(statementModel) {
+                                +utilsClassId[setField](
+                                    instance,
+                                    fieldId.declaringClass.name,
+                                    fieldId.name,
+                                    fieldValue
+                                )
+                            }
                         }
+                    } else {
+                        instance[statementModel.fieldId] `=` declareOrGet(statementModel.fieldModel)
                     }
                 }
                 is UtExecutableCallModel -> {
diff --git a/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/util/DslUtil.kt b/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/util/DslUtil.kt
index 2429d6b0ac..228654457d 100644
--- a/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/util/DslUtil.kt
+++ b/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/util/DslUtil.kt
@@ -46,8 +46,6 @@ infix fun CgExpression.greaterThan(other: Any?): CgGreaterThan =
 // TODO: is it OK to use Object as a type of null literal?
 fun nullLiteral() = CgLiteral(objectClassId, null)
 
-fun nullLiteralWithCast(classId: ClassId) = CgLiteral(classId, null)
-
 fun intLiteral(num: Int) = CgLiteral(intClassId, num)
 
 fun longLiteral(num: Long) = CgLiteral(longClassId, num)
diff --git a/utbot-framework/src/main/kotlin/org/utbot/framework/plugin/api/TestCaseGenerator.kt b/utbot-framework/src/main/kotlin/org/utbot/framework/plugin/api/TestCaseGenerator.kt
index a13b5b1558..b0832725c4 100644
--- a/utbot-framework/src/main/kotlin/org/utbot/framework/plugin/api/TestCaseGenerator.kt
+++ b/utbot-framework/src/main/kotlin/org/utbot/framework/plugin/api/TestCaseGenerator.kt
@@ -43,7 +43,6 @@ import org.utbot.instrumentation.warmup
 import java.io.File
 import java.nio.file.Path
 import kotlin.coroutines.cancellation.CancellationException
-import kotlin.io.path.appendText
 import kotlin.math.min
 
 /**
@@ -231,6 +230,9 @@ open class TestCaseGenerator(
         }
         ConcreteExecutor.defaultPool.close() // TODO: think on appropriate way to close instrumented processes
 
+        forceMockListener.detach(this, forceMockListener)
+        forceStaticMockListener.detach(this, forceStaticMockListener)
+
         if (UtSettings.useGreyBoxFuzzing) {
             GreyBoxFuzzingStatisticPrinter.printFuzzingStats(method2executions)
         }
diff --git a/utbot-framework/src/main/kotlin/org/utbot/framework/util/SootUtils.kt b/utbot-framework/src/main/kotlin/org/utbot/framework/util/SootUtils.kt
index 26c749c920..e95e76f5ea 100644
--- a/utbot-framework/src/main/kotlin/org/utbot/framework/util/SootUtils.kt
+++ b/utbot-framework/src/main/kotlin/org/utbot/framework/util/SootUtils.kt
@@ -131,6 +131,7 @@ val ExecutableId.sootMethod: SootMethod
 fun jimpleBody(method: ExecutableId): JimpleBody =
     method.sootMethod.jimpleBody()
 
+
 private fun addBasicClasses(vararg classes: Class<*>) {
     classes.forEach {
         Scene.v().addBasicClass(it.name, SootClass.BODIES)
diff --git a/utbot-instrumentation/src/main/kotlin/org/utbot/instrumentation/instrumentation/et/TraceHandler.kt b/utbot-instrumentation/src/main/kotlin/org/utbot/instrumentation/instrumentation/et/TraceHandler.kt
index 9968382e0f..e377adf17a 100644
--- a/utbot-instrumentation/src/main/kotlin/org/utbot/instrumentation/instrumentation/et/TraceHandler.kt
+++ b/utbot-instrumentation/src/main/kotlin/org/utbot/instrumentation/instrumentation/et/TraceHandler.kt
@@ -233,12 +233,6 @@ class TraceHandler {
         return instructionsList!!
     }
 
-    fun getMethodInstructions(className: String, methodSignature: String) =
-        processingStorage.instructionsData.entries.filter {
-            val insClassName = processingStorage.computeClassNameAndLocalId(it.key).first
-            insClassName == className && it.value.methodSignature == methodSignature
-        }
-
     fun computePutStatics(): List<FieldId> =
         computeInstructionList().map { it.instructionData }
             .filterIsInstance<PutStaticInstruction>()
diff --git a/utbot-instrumentation/src/main/kotlin/org/utbot/instrumentation/instrumentation/execution/UtExecutionInstrumentation.kt b/utbot-instrumentation/src/main/kotlin/org/utbot/instrumentation/instrumentation/execution/UtExecutionInstrumentation.kt
index eb7a939bb0..accb4f3321 100644
--- a/utbot-instrumentation/src/main/kotlin/org/utbot/instrumentation/instrumentation/execution/UtExecutionInstrumentation.kt
+++ b/utbot-instrumentation/src/main/kotlin/org/utbot/instrumentation/instrumentation/execution/UtExecutionInstrumentation.kt
@@ -20,7 +20,6 @@ import org.utbot.framework.plugin.api.util.singleExecutableId
 import org.utbot.instrumentation.instrumentation.ArgumentList
 import org.utbot.instrumentation.instrumentation.Instrumentation
 import org.utbot.instrumentation.instrumentation.InvokeInstrumentation
-import org.utbot.instrumentation.instrumentation.et.EtInstruction
 import org.utbot.instrumentation.instrumentation.et.TraceHandler
 import org.utbot.instrumentation.instrumentation.instrumenter.Instrumenter
 import org.utbot.instrumentation.instrumentation.mock.MockClassVisitor
@@ -198,12 +197,3 @@ object UtExecutionInstrumentation : Instrumentation<UtConcreteExecutionResult> {
         return instrumenter.classByteCode
     }
 }
-
-/**
- * Transforms a list of internal [EtInstruction]s to a list of api [Instruction]s.
- */
-internal fun List<EtInstruction>.toApiCoverage(instructionsCount: Long? = null): Coverage =
-    Coverage(
-        map { Instruction(it.className, it.methodSignature, it.line, it.id) },
-        instructionsCount
-    )
diff --git a/utbot-instrumentation/src/main/kotlin/org/utbot/instrumentation/instrumentation/execution/UtExecutionInstrumentationWithStatsCollection.kt b/utbot-instrumentation/src/main/kotlin/org/utbot/instrumentation/instrumentation/execution/UtExecutionInstrumentationWithStatsCollection.kt
index b5ed9e2a97..2bb8b0c069 100644
--- a/utbot-instrumentation/src/main/kotlin/org/utbot/instrumentation/instrumentation/execution/UtExecutionInstrumentationWithStatsCollection.kt
+++ b/utbot-instrumentation/src/main/kotlin/org/utbot/instrumentation/instrumentation/execution/UtExecutionInstrumentationWithStatsCollection.kt
@@ -1,7 +1,6 @@
 package org.utbot.framework.concrete
 
 import org.utbot.framework.plugin.api.*
-import org.utbot.instrumentation.instrumentation.ArgumentList
 import org.utbot.instrumentation.instrumentation.Instrumentation
 import org.utbot.instrumentation.instrumentation.InvokeInstrumentation
 import org.utbot.instrumentation.instrumentation.et.ExplicitThrowInstruction
diff --git a/utbot-instrumentation/src/main/kotlin/org/utbot/instrumentation/instrumentation/execution/UtFuzzingExecutionInstrumentation.kt b/utbot-instrumentation/src/main/kotlin/org/utbot/instrumentation/instrumentation/execution/UtFuzzingExecutionInstrumentation.kt
index 6c36aef223..7020822a61 100644
--- a/utbot-instrumentation/src/main/kotlin/org/utbot/instrumentation/instrumentation/execution/UtFuzzingExecutionInstrumentation.kt
+++ b/utbot-instrumentation/src/main/kotlin/org/utbot/instrumentation/instrumentation/execution/UtFuzzingExecutionInstrumentation.kt
@@ -14,9 +14,6 @@ import org.utbot.instrumentation.instrumentation.execution.phases.PhaseError
 import org.utbot.instrumentation.instrumentation.execution.phases.PhasesController
 import org.utbot.instrumentation.instrumentation.execution.phases.start
 import java.security.AccessControlException
-import kotlin.io.path.Path
-import kotlin.io.path.appendText
-import kotlin.io.path.writeText
 
 object UtFuzzingExecutionInstrumentation : UtExecutionInstrumentationWithStatsCollection {
 
diff --git a/utbot-instrumentation/src/main/kotlin/org/utbot/instrumentation/instrumentation/execution/constructors/MockValueConstructor.kt b/utbot-instrumentation/src/main/kotlin/org/utbot/instrumentation/instrumentation/execution/constructors/MockValueConstructor.kt
index 96bca189a8..3d821248b2 100644
--- a/utbot-instrumentation/src/main/kotlin/org/utbot/instrumentation/instrumentation/execution/constructors/MockValueConstructor.kt
+++ b/utbot-instrumentation/src/main/kotlin/org/utbot/instrumentation/instrumentation/execution/constructors/MockValueConstructor.kt
@@ -83,7 +83,7 @@ class MockValueConstructor(
         }
 
     // TODO: JIRA:1379 -- replace UtReferenceModel with Int
-    private val constructedObjects = HashMap<UtReferenceModel, Any?>()
+    private val constructedObjects = HashMap<UtReferenceModel, Any>()
     private val mockInfo = mutableListOf<MockInfo>()
     private var mockTarget: MockTarget? = null
     private var mockCounter = 0
@@ -213,12 +213,7 @@ class MockValueConstructor(
             check(Reflection.isModifiersAccessible())
 
             val target = mockTarget(fieldModel) {
-                FieldMockTarget(
-                    fieldModel.classId.name,
-                    model.classId.name,
-                    UtConcreteValue(classInstance),
-                    fieldId.name
-                )
+                FieldMockTarget(fieldModel.classId.name, model.classId.name, UtConcreteValue(classInstance), fieldId.name)
             }
             val value = construct(fieldModel, target).value
             val instance = if (Modifier.isStatic(declaredField.modifiers)) null else classInstance
@@ -367,10 +362,9 @@ class MockValueConstructor(
                         val value = construct(elementModel, null).value
                         try {
                             java.lang.reflect.Array.set(instance, i, value)
-                        } catch (iae: IllegalArgumentException) {
+                        } catch (iae:IllegalArgumentException) {
                             throw IllegalArgumentException(
-                                iae.message + " array: ${instance.javaClass.name}; value: ${value?.javaClass?.name}",
-                                iae
+                                iae.message + " array: ${instance.javaClass.name}; value: ${value?.javaClass?.name}" , iae
                             )
                         }
                     }
@@ -383,18 +377,15 @@ class MockValueConstructor(
     /**
      * Constructs object with [UtAssembleModel].
      */
-    private fun constructFromAssembleModel(assembleModel: UtAssembleModel): Any? {
+    private fun constructFromAssembleModel(assembleModel: UtAssembleModel): Any {
         constructedObjects[assembleModel]?.let { return it }
 
         val instantiationExecutableCall = assembleModel.instantiationCall
         val result = updateWithExecutableCallModel(instantiationExecutableCall)
-//        checkNotNull(result) {
-//            "Tracked instance can't be null for call ${instantiationExecutableCall.executable} in model $assembleModel"
-//        }
-        constructedObjects[assembleModel] = result
-        if (result == null) {
-            return null
+        checkNotNull(result) {
+            "Tracked instance can't be null for call ${instantiationExecutableCall.executable} in model $assembleModel"
         }
+        constructedObjects[assembleModel] = result
 
         assembleModel.modificationsChain.forEach { statementModel ->
             when (statementModel) {
@@ -510,13 +501,8 @@ class MockValueConstructor(
         }
 
     private fun ConstructorId.call(args: List<Any?>): Any? =
-        try {
-            constructor.runSandbox {
-                this.isAccessible = true
-                newInstance(*args.toTypedArray())
-            }
-        } catch (e: Throwable) {
-            null
+        constructor.runSandbox {
+            newInstance(*args.toTypedArray())
         }
 
     /**
diff --git a/utbot-instrumentation/src/main/kotlin/org/utbot/instrumentation/instrumentation/mock/MockClassVisitor.kt b/utbot-instrumentation/src/main/kotlin/org/utbot/instrumentation/instrumentation/mock/MockClassVisitor.kt
index 4ce875c12a..ec108974e3 100644
--- a/utbot-instrumentation/src/main/kotlin/org/utbot/instrumentation/instrumentation/mock/MockClassVisitor.kt
+++ b/utbot-instrumentation/src/main/kotlin/org/utbot/instrumentation/instrumentation/mock/MockClassVisitor.kt
@@ -96,36 +96,36 @@ class MockClassVisitor(
 
             private val afterLabels: MutableList<Label> = mutableListOf()
 
-//            override fun visitTypeInsn(opcode: Int, type: String?) {
-//                if (opcode == NEW) {
-//                    val afterLabel = Label()
-//                    afterLabels.add(afterLabel)
-//                    val newLabel = Label()
-//
-//                    // if (callSiteCheck(type, class))
-//                    push(type)
-//                    push(internalClassName)
-//                    invokeStatic(callSiteCheckerOwner, callSiteCheckerMethod)
-//                    ifZCmp(IFEQ, newLabel)
-//
-//                    // if (hasMock(null, type.<init>))
-//                    visitInsn(ACONST_NULL)
-//                    push("$type.<init>")
-//                    invokeStatic(hasMockOwner, hasMockMethod)
-//                    ifZCmp(IFEQ, newLabel)
-//
-//                    // getMock(null, type.<init>)
-//                    visitInsn(ACONST_NULL)
-//                    push("$type.<init>")
-//                    invokeStatic(mockGetterOwner, mockGetterMethod)
-//                    visitTypeInsn(CHECKCAST, type)
-//                    goTo(afterLabel)
-//
-//                    // else
-//                    visitLabel(newLabel)
-//                }
-//                super.visitTypeInsn(opcode, type)
-//            }
+            override fun visitTypeInsn(opcode: Int, type: String?) {
+                if (opcode == NEW) {
+                    val afterLabel = Label()
+                    afterLabels.add(afterLabel)
+                    val newLabel = Label()
+
+                    // if (callSiteCheck(type, class))
+                    push(type)
+                    push(internalClassName)
+                    invokeStatic(callSiteCheckerOwner, callSiteCheckerMethod)
+                    ifZCmp(IFEQ, newLabel)
+
+                    // if (hasMock(null, type.<init>))
+                    visitInsn(ACONST_NULL)
+                    push("$type.<init>")
+                    invokeStatic(hasMockOwner, hasMockMethod)
+                    ifZCmp(IFEQ, newLabel)
+
+                    // getMock(null, type.<init>)
+                    visitInsn(ACONST_NULL)
+                    push("$type.<init>")
+                    invokeStatic(mockGetterOwner, mockGetterMethod)
+                    visitTypeInsn(CHECKCAST, type)
+                    goTo(afterLabel)
+
+                    // else
+                    visitLabel(newLabel)
+                }
+                super.visitTypeInsn(opcode, type)
+            }
 
             override fun visitMethodInsn(
                 opcodeAndSource: Int,
diff --git a/utbot-junit-contest/src/main/kotlin/org/utbot/contest/Contest.kt b/utbot-junit-contest/src/main/kotlin/org/utbot/contest/Contest.kt
index cce5a5e7b3..0505a259d8 100644
--- a/utbot-junit-contest/src/main/kotlin/org/utbot/contest/Contest.kt
+++ b/utbot-junit-contest/src/main/kotlin/org/utbot/contest/Contest.kt
@@ -277,7 +277,7 @@ fun runGeneration(
                     val methodJob = currentCoroutineContext().job
 
                     logger.debug { " ... " }
-                    val statsForMethod = StatsForMethod("${method.classId.simpleName}#${method.name}#${method.signature}", Type.getInternalName(method.classId.jClass))
+                    val statsForMethod = StatsForMethod("${method.classId.simpleName}#${method.name}")
                     statsForClass.statsForMethods.add(statsForMethod)