diff --git a/ParseTree/ParseTree.Src/Nodes/OperationNode.cs b/ParseTree/ParseTree.Src/Nodes/OperationNode.cs
index b176098..26a1137 100644
--- a/ParseTree/ParseTree.Src/Nodes/OperationNode.cs
+++ b/ParseTree/ParseTree.Src/Nodes/OperationNode.cs
@@ -24,7 +24,7 @@ public override string ToString()
     {
         if (LeftChild is not null && RightChild is not null)
         {
-            return $"( {operation} {LeftChild.ToString()} {RightChild.ToString()})";
+            return $"({operation} {LeftChild.ToString()} {RightChild.ToString()})";
         }
         throw new IncorrectTreeException();
     }
diff --git a/ParseTree/ParseTree.Src/Operation.cs b/ParseTree/ParseTree.Src/Operation.cs
index 006b49f..b5b2174 100644
--- a/ParseTree/ParseTree.Src/Operation.cs
+++ b/ParseTree/ParseTree.Src/Operation.cs
@@ -2,8 +2,20 @@
 
 namespace ParseTree.Dependencies;
 
+/// <summary>
+/// Class implementing arithmetic operations based on char input
+/// </summary>
 class Operation
 {
+    /// <summary>
+    /// Do the arithmetic operation corresponding to char
+    /// </summary>
+    /// <param name="operation">Char '*', '+', '-' or '/'</param>
+    /// <param name="operandLeft">Left operand</param>
+    /// <param name="operandRight">Right operand</param>
+    /// <returns>Result of the operation</returns>
+    /// <exception cref="DivideByZeroException">Thrown if operandRight is 0 and operation is '/'</exception>
+    /// <exception cref="IncorrectExpressionException">thrown if argument operation is something different to '*', '+', '-' or '/'</exception>
     public static double Calculate(char operation, double operandLeft, double operandRight)
     {
         switch (operation)
diff --git a/ParseTree/ParseTree.Src/Tree.cs b/ParseTree/ParseTree.Src/Tree.cs
index 0053de2..50f3452 100644
--- a/ParseTree/ParseTree.Src/Tree.cs
+++ b/ParseTree/ParseTree.Src/Tree.cs
@@ -44,6 +44,7 @@ private static INode Parse(string expression, ref int index)
         if (currentChar == '(')
         {
             ++index;
+            SkipSpaces(expression, ref index);
             newNode = new OperationNode(expression[index]);
             ++index;
             newNode.LeftChild = Parse(expression, ref index);
diff --git a/ParseTree/ParseTree.Tests/ParseTree.Tests.cs b/ParseTree/ParseTree.Tests/ParseTree.Tests.cs
index 5883500..f51bf49 100644
--- a/ParseTree/ParseTree.Tests/ParseTree.Tests.cs
+++ b/ParseTree/ParseTree.Tests/ParseTree.Tests.cs
@@ -5,7 +5,7 @@ namespace ParseTree.Tests;
 
 public class Tests
 {
-    [TestCase("(* (+ 1 1) 2)", 4)]
+    [TestCase("(  * (+ 1 1 ) 2 )", 4)]
     [TestCase("5", 5)]
     [TestCase("(/ 5 2)", 2.5)]
     public void TestEvaluation(string expression, double expectedResult)
@@ -24,5 +24,16 @@ public void IncorrectInputTest(string expression)
     {
         Assert.Throws<IncorrectExpressionException>(() => new Tree(expression));
     }
+
+    [TestCase("(* (+ 1 1) 2)")]
+    [TestCase("5")]
+    [TestCase("(/ 5 2)")]
+    public void ToStringTests(string expression)
+    {
+        var tree = new Tree(expression);
+        var result = tree.ToString();
+
+        Assert.That(result, Is.EqualTo(expression));
+    }
 }
  
\ No newline at end of file