поправил пути

LR1/AppTesting/Program.cs

@@ -4,7 +4,7 @@ public class Program
 {
     private static void Main()
     {
-        double[] inputArray = ReadData(@"..\..\..\..\TestData\input_data.txt");
+        double[] inputArray = ReadData(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "TestData", "input_data.txt"));
         Console.WriteLine($"Input data: [{string.Join("; ", inputArray)}]");
 
         var outputData = ArrayProc(inputArray);