Sometimes the Windows Path variable exceeds 2048 characters, which can lead to errors in many applications and the Windows OS itself. This is a series of tests to check this and possibly fix.

PathVariableTests.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using NUnit.Framework;

namespace PathTests
{
    [TestFixture]
    public class PathVariableTests
    {
        [Test]
        public void PathVariable_IsLessThan2048Characters()
        {
            var pathVariable = Environment.GetEnvironmentVariable("Path", EnvironmentVariableTarget.Machine);

            Console.WriteLine("Path Variable length is {0} characters",pathVariable.Length);

            Assert.That(pathVariable.Length,Is.LessThanOrEqualTo(2048));
        }

        [Test]
        public void PathVariable_DistinctValues_IsLessThan2048Characters()
        {
            var pathVariable = Environment.GetEnvironmentVariable("Path", EnvironmentVariableTarget.Machine);

            var uniquePaths = pathVariable.Split(';').Distinct().ToList();
            var pathWithUniqueOnly = string.Join(";", uniquePaths);

            Console.WriteLine("Path Variable length is {0} characters", pathVariable.Length);
            Console.WriteLine("There are {0} unique paths in the path variable", uniquePaths.Count);
            Console.WriteLine("Path Variable length with unique paths is {0} characters", pathWithUniqueOnly.Length);

            Assert.That(pathWithUniqueOnly.Length,Is.LessThanOrEqualTo(2048));
        }

        [Test]
        public void PathVariable_DistinctValuesAndPathExists_IsLessThan2048Characters()
        {
            var pathVariable = Environment.GetEnvironmentVariable("Path", EnvironmentVariableTarget.Machine);

            var uniquePaths = pathVariable.Split(';')
                .Distinct()
                 .Where(Directory.Exists)
                .ToList();
            var pathWithUniqueOnly = string.Join(";", uniquePaths);

            Console.WriteLine("Path Variable length is {0} characters", pathVariable.Length);
            Console.WriteLine("There are {0} unique paths in the path variable", uniquePaths.Count);
            Console.WriteLine("Path Variable length with unique paths is {0} characters", pathWithUniqueOnly.Length);

            Assert.That(pathWithUniqueOnly.Length, Is.LessThanOrEqualTo(2048));
        }

        [Test]
        public void PathVariable_ListPaths()
        {
            var pathVariable = Environment.GetEnvironmentVariable("Path", EnvironmentVariableTarget.Machine);

            var uniquePaths = pathVariable.Split(';').Distinct().OrderBy(p=>p).ToList();
           
            uniquePaths.ForEach(Console.WriteLine);
        }

        [Test]
        public void PathVariable_PathsInVaraible_ShouldExist()
        {
            var pathVariable = Environment.GetEnvironmentVariable("Path", EnvironmentVariableTarget.Machine);

            var pathExistence = pathVariable.Split(';')
                .Distinct()
                .Select(p=>new {Path=p,Exists = Directory.Exists(p)})
                .ToList();

            var maximumPathLength = pathExistence.Select(p => p.Path.Length).Max();
            Console.WriteLine("|Exists|{0}|", "Directory".PadRight(maximumPathLength));
            foreach (var path in pathExistence)
            {
                Console.WriteLine("|{0}|{1}|", path.Exists.ToString().PadRight(6), path.Path.PadRight(maximumPathLength));
            }

            Assert.That(pathExistence.All(p=>p.Exists),"There is at least 1 path that does not exist");
        }

        [Test]
        public void PathVariable_SetToUniquePathsThatExist()
        {
            var pathVariable = Environment.GetEnvironmentVariable("Path", EnvironmentVariableTarget.Machine);

            var pathsThatExist = pathVariable.Split(';')
                .Distinct()
                .Where(Directory.Exists)
                .ToList();

            var newPathVariable = string.Join(";", pathsThatExist);

            Console.WriteLine("Old Path Variable is: \r\n'{0}'",pathVariable);
            Console.WriteLine("----------------------------------------------------------------------------");
            Console.WriteLine("New Path Variable is: \r\n'{0}'", newPathVariable);

            // Only do this if you want to update the Path
            //Environment.SetEnvironmentVariable("Path", newPathVariable,EnvironmentVariableTarget.Machine);
        }
    }
}