diff --git a/test/functional-tests/stack-trace-analyzer/StackTraceAnalyzer.spec.ts b/test/functional-tests/stack-trace-analyzer/StackTraceAnalyzer.spec.ts
index b4a34f36..64987716 100644
--- a/test/functional-tests/stack-trace-analyzer/StackTraceAnalyzer.spec.ts
+++ b/test/functional-tests/stack-trace-analyzer/StackTraceAnalyzer.spec.ts
@@ -151,7 +151,7 @@ describe('StackTraceAnalyzer', () => {
 
         it('should returns correct IStackTraceData - variant #1: basic-1', () => {
             astTree = NodeMocks.getProgramNode(
-                <ESTree.Statement[]>NodeUtils.convertCodeToStructure(
+                NodeUtils.convertCodeToStructure(
                     readFileAsString('./test/fixtures/stack-trace-analyzer/basic-1.js')
                 )
             );
@@ -198,7 +198,7 @@ describe('StackTraceAnalyzer', () => {
 
         it('should returns correct BlockScopeTraceData - variant #2: basic-2', () => {
             astTree = NodeMocks.getProgramNode(
-                <ESTree.Statement[]>NodeUtils.convertCodeToStructure(
+                NodeUtils.convertCodeToStructure(
                     readFileAsString('./test/fixtures/stack-trace-analyzer/basic-2.js')
                 )
             );
@@ -234,7 +234,7 @@ describe('StackTraceAnalyzer', () => {
 
         it('should returns correct BlockScopeTraceData - variant #3: deep conditions nesting', () => {
             astTree = NodeMocks.getProgramNode(
-                <ESTree.Statement[]>NodeUtils.convertCodeToStructure(
+                NodeUtils.convertCodeToStructure(
                     readFileAsString('./test/fixtures/stack-trace-analyzer/deep-conditions-nesting.js')
                 )
             );
@@ -270,7 +270,7 @@ describe('StackTraceAnalyzer', () => {
 
         it('should returns correct BlockScopeTraceData - variant #4: call before declaration', () => {
             astTree = NodeMocks.getProgramNode(
-                <ESTree.Statement[]>NodeUtils.convertCodeToStructure(
+                NodeUtils.convertCodeToStructure(
                     readFileAsString('./test/fixtures/stack-trace-analyzer/call-before-declaration.js')
                 )
             );
@@ -290,7 +290,7 @@ describe('StackTraceAnalyzer', () => {
 
         it('should returns correct BlockScopeTraceData - variant #5: call expression of object member', () => {
             astTree = NodeMocks.getProgramNode(
-                <ESTree.Statement[]>NodeUtils.convertCodeToStructure(
+                NodeUtils.convertCodeToStructure(
                     readFileAsString('./test/fixtures/stack-trace-analyzer/call-expression-of-object-member.js')
                 )
             );
@@ -346,7 +346,7 @@ describe('StackTraceAnalyzer', () => {
 
         it('should returns correct BlockScopeTraceData - variant #6: no call expressions', () => {
             astTree = NodeMocks.getProgramNode(
-                <ESTree.Statement[]>NodeUtils.convertCodeToStructure(
+                NodeUtils.convertCodeToStructure(
                     readFileAsString('./test/fixtures/stack-trace-analyzer/no-call-expressions.js')
                 )
             );
@@ -360,7 +360,7 @@ describe('StackTraceAnalyzer', () => {
 
         it('should returns correct BlockScopeTraceData - variant #7: only call expression', () => {
             astTree = NodeMocks.getProgramNode(
-                <ESTree.Statement[]>NodeUtils.convertCodeToStructure(
+                NodeUtils.convertCodeToStructure(
                     readFileAsString('./test/fixtures/stack-trace-analyzer/only-call-expression.js')
                 )
             );
@@ -374,7 +374,7 @@ describe('StackTraceAnalyzer', () => {
 
         it('should returns correct BlockScopeTraceData - variant #8: self-invoking functions', () => {
             astTree = NodeMocks.getProgramNode(
-                <ESTree.Statement[]>NodeUtils.convertCodeToStructure(
+                NodeUtils.convertCodeToStructure(
                     readFileAsString('./test/fixtures/stack-trace-analyzer/self-invoking-functions.js')
                 )
             );
@@ -406,7 +406,7 @@ describe('StackTraceAnalyzer', () => {
 
         it('should returns correct BlockScopeTraceData - variant #9: no recursion', () => {
             astTree = NodeMocks.getProgramNode(
-                <ESTree.Statement[]>NodeUtils.convertCodeToStructure(
+                NodeUtils.convertCodeToStructure(
                     readFileAsString('./test/fixtures/stack-trace-analyzer/no-recursion.js')
                 )
             );
diff --git a/test/mocks/NodeMocks.ts b/test/mocks/NodeMocks.ts
index e4cfc472..5802e8a4 100644
--- a/test/mocks/NodeMocks.ts
+++ b/test/mocks/NodeMocks.ts
@@ -1,6 +1,8 @@
 import * as escodegen from 'escodegen';
 import * as ESTree from 'estree';
 
+import { TStatement } from '../../src/types/TStatement';
+
 import { NodeType } from '../../src/enums/NodeType';
 
 export class NodeMocks {
@@ -8,7 +10,7 @@ export class NodeMocks {
      * @param bodyNodes
      * @returns {ESTree.Program}
      */
-    public static getProgramNode (bodyNodes: ESTree.Statement[] = []): ESTree.Program {
+    public static getProgramNode (bodyNodes: TStatement[] = []): ESTree.Program {
         return {
             type: NodeType.Program,
             body: bodyNodes,
diff --git a/test/unit-tests/NodeUtils.spec.ts b/test/unit-tests/NodeUtils.spec.ts
index 5f920bf2..f66b8e8a 100644
--- a/test/unit-tests/NodeUtils.spec.ts
+++ b/test/unit-tests/NodeUtils.spec.ts
@@ -27,7 +27,7 @@ describe('NodeUtils', () => {
         });
     });
 
-    describe('appendNode (blockScopeNode: TNodeWithBlockStatement[], nodeBodyStatements: TStatement[])', () => {
+    describe('appendNode (blockScopeNode: TNodeWithBlockStatement[], nodeBodyStatements: TStatement[]): void', () => {
         let blockStatementNode: ESTree.BlockStatement,
             expectedBlockStatementNode: ESTree.BlockStatement,
             expectedExpressionStatementNode: ESTree.ExpressionStatement,
@@ -198,7 +198,7 @@ describe('NodeUtils', () => {
         });
     });
 
-    describe('insertNodeAtIndex (blockScopeNode: TNodeWithBlockStatement[], nodeBodyStatements: TStatement[], index: number): TNodeWithBlockStatement[]', () => {
+    describe('insertNodeAtIndex (blockScopeNode: TNodeWithBlockStatement[], nodeBodyStatements: TStatement[], index: number): void', () => {
         let blockStatementNode: ESTree.BlockStatement,
             expectedBlockStatementNode: ESTree.BlockStatement,
             expressionStatementNode1: ESTree.ExpressionStatement,
@@ -296,7 +296,7 @@ describe('NodeUtils', () => {
         });
     });
 
-    describe('prependNode (blockScopeNode: TNodeWithBlockStatement[], nodeBodyStatements: TStatement[]): TNodeWithBlockStatement[]', () => {
+    describe('prependNode (blockScopeNode: TNodeWithBlockStatement[], nodeBodyStatements: TStatement[]): void', () => {
         let blockStatementNode: ESTree.BlockStatement,
             expectedBlockStatementNode: ESTree.BlockStatement,
             expressionStatementNode1: ESTree.ExpressionStatement,
diff --git a/test/unit-tests/custom-nodes/CustomNodeAppender.spec.ts b/test/unit-tests/custom-nodes/CustomNodeAppender.spec.ts
index 3c00eb02..38d65f5e 100644
--- a/test/unit-tests/custom-nodes/CustomNodeAppender.spec.ts
+++ b/test/unit-tests/custom-nodes/CustomNodeAppender.spec.ts
@@ -13,7 +13,7 @@ import { StackTraceAnalyzer } from '../../../src/stack-trace-analyzer/StackTrace
 const assert: any = chai.assert;
 
 describe('CustomNodeAppender', () => {
-    describe('appendNode (blockScopeStackTraceData: IStackTraceData[], blockScopeNode: TNodeWithBlockStatement, nodeBodyStatements: TStatement[], index: number = 0)', () => {
+    describe('appendNode (blockScopeStackTraceData: IStackTraceData[], blockScopeNode: TNodeWithBlockStatement, nodeBodyStatements: TStatement[], index: number = 0): void', () => {
         let astTree: ESTree.Program,
             expectedAstTree: ESTree.Program,
             node: TStatement[],