CliFx/CliFx.Analyzers.Tests/GeneralSpecs.cs

using System;
using System.Linq;
using FluentAssertions;
using Microsoft.CodeAnalysis.Diagnostics;
using Xunit;

namespace CliFx.Analyzers.Tests
{
    public class GeneralSpecs
    {
        [Fact]
        public void All_analyzers_have_unique_diagnostic_IDs()
        {
            // Arrange
            var analyzers = typeof(AnalyzerBase)
                .Assembly
                .GetTypes()
                .Where(t => !t.IsAbstract && t.IsAssignableTo(typeof(DiagnosticAnalyzer)))
                .Select(t => (DiagnosticAnalyzer) Activator.CreateInstance(t)!)
                .ToArray();

            // Act
            var diagnosticIds = analyzers
                .SelectMany(a => a.SupportedDiagnostics.Select(d => d.Id))
                .ToArray();

            // Assert
            diagnosticIds.Should().OnlyHaveUniqueItems();
        }
    }
}