diff --git a/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/model/constructor/CgMethodTestSet.kt b/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/model/constructor/CgMethodTestSet.kt
index a58b1007b5..cf47bea1ec 100644
--- a/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/model/constructor/CgMethodTestSet.kt
+++ b/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/model/constructor/CgMethodTestSet.kt
@@ -5,6 +5,7 @@ import org.utbot.framework.plugin.api.ExecutableId
 import org.utbot.framework.plugin.api.FieldId
 import org.utbot.framework.plugin.api.UtClusterInfo
 import org.utbot.framework.plugin.api.UtExecution
+import org.utbot.framework.plugin.api.UtExecutionFailure
 import org.utbot.framework.plugin.api.UtExecutionSuccess
 import org.utbot.framework.plugin.api.UtMethodTestSet
 import org.utbot.framework.plugin.api.util.executableId
@@ -36,12 +37,19 @@ data class CgMethodTestSet private constructor(
      */
     fun splitExecutionsByResult() : List<CgMethodTestSet> {
         val successfulExecutions = executions.filter { it.result is UtExecutionSuccess }
-        val executionsByResult: Map<ClassId, List<UtExecution>> =
-            if (successfulExecutions.isNotEmpty()) {
-                successfulExecutions.groupBy { (it.result as UtExecutionSuccess).model.classId }
-            } else {
-                mapOf(objectClassId to executions)
-            }
+        val failureExecutions = executions.filter { it.result is UtExecutionFailure }
+
+        val executionsByResult: MutableMap<ClassId, List<UtExecution>> =
+            successfulExecutions
+                .groupBy { (it.result as UtExecutionSuccess).model.classId }.toMutableMap()
+
+        // if we have failure executions, we add them to the first successful executions group
+        val groupClassId = executionsByResult.keys.firstOrNull()
+        if (groupClassId != null) {
+            executionsByResult[groupClassId] = executionsByResult[groupClassId]!! + failureExecutions
+        } else {
+            executionsByResult[objectClassId] = failureExecutions
+        }
 
         return executionsByResult.map{ (_, executions) -> substituteExecutions(executions) }
     }
@@ -52,15 +60,8 @@ data class CgMethodTestSet private constructor(
      * A separate test set is created for each combination of modified statics.
      */
     fun splitExecutionsByChangedStatics(): List<CgMethodTestSet> {
-        val successfulExecutions = executions.filter { it.result is UtExecutionSuccess }
         val executionsByStaticsUsage: Map<Set<FieldId>, List<UtExecution>> =
-            if (successfulExecutions.isNotEmpty()) {
-                successfulExecutions.groupBy {
-                    it.stateBefore.statics.keys
-                }
-            } else {
-                mapOf(executions.first().stateBefore.statics.keys to executions)
-            }
+            executions.groupBy { it.stateBefore.statics.keys }
 
         return executionsByStaticsUsage.map { (_, executions) -> substituteExecutions(executions) }
     }
diff --git a/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/model/constructor/tree/CgMethodConstructor.kt b/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/model/constructor/tree/CgMethodConstructor.kt
index de071c9eb1..92a8e0320b 100644
--- a/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/model/constructor/tree/CgMethodConstructor.kt
+++ b/utbot-framework/src/main/kotlin/org/utbot/framework/codegen/model/constructor/tree/CgMethodConstructor.kt
@@ -783,7 +783,7 @@ internal class CgMethodConstructor(val context: CgContext) : CgContextOwner by c
 
                     ifStatement(
                         CgEqualTo(expectedNestedElement, nullLiteral()),
-                        trueBranch = { assertions[assertNull](actualNestedElement).toStatement() },
+                        trueBranch = { +assertions[assertNull](actualNestedElement).toStatement() },
                         falseBranch = {
                             floatingPointArraysDeepEquals(
                                 expectedArrayInfo.getNested(),
@@ -1055,7 +1055,7 @@ internal class CgMethodConstructor(val context: CgContext) : CgContextOwner by c
                 actual.type.isPrimitive -> generateDeepEqualsAssertion(expected, actual)
                 else -> ifStatement(
                     CgEqualTo(expected, nullLiteral()),
-                    trueBranch = { testFrameworkManager.assertions[testFramework.assertNull](actual).toStatement() },
+                    trueBranch = { +testFrameworkManager.assertions[testFramework.assertNull](actual).toStatement() },
                     falseBranch = { generateDeepEqualsAssertion(expected, actual) }
                 )
             }
@@ -1188,7 +1188,8 @@ internal class CgMethodConstructor(val context: CgContext) : CgContextOwner by c
         //may be a heuristic to select a model with minimal number of internal nulls should be used
         val genericExecution = testSet.executions
             .firstOrNull { it.result is UtExecutionSuccess && (it.result as UtExecutionSuccess).model !is UtNullModel }
-            ?: testSet.executions.first()
+            ?: testSet.executions
+                .firstOrNull { it.result is UtExecutionSuccess } ?: testSet.executions.first()
 
         val statics = genericExecution.stateBefore.statics