Deduplicate target frameworks

In the ApproveApi test, read the target frameworks directly from the FluentAssertions.csproj file instead of copying them all as InlineData.

This should future proof when new target frameworks are added/removed from the main project.

Tests/Approval.Tests/ApiApproval.cs

@@ -5,6 +5,8 @@
 using System.Runtime.CompilerServices;
 using System.Text;
 using System.Threading.Tasks;
+using System.Xml.Linq;
+using System.Xml.XPath;
 using DiffPlex.DiffBuilder;
 using DiffPlex.DiffBuilder.Model;
 using PublicApiGenerator;
@@ -18,12 +20,7 @@ namespace Approval.Tests;
 public class ApiApproval
 {
     [Theory]
-    [InlineData("net47")]
-    [InlineData("net6.0")]
-    [InlineData("netstandard2.0")]
-    [InlineData("netstandard2.1")]
-    [InlineData("netcoreapp2.1")]
-    [InlineData("netcoreapp3.0")]
+    [ClassData(typeof(TargetFrameworksTheoryData))]
     public Task ApproveApi(string frameworkVersion)
     {
         string codeBase = Assembly.GetExecutingAssembly().Location;
@@ -75,4 +72,18 @@ public static Task<CompareResult> OnlyIncludeChanges(string received, string ver
         var compareResult = CompareResult.NotEqual(builder.ToString());
         return Task.FromResult(compareResult);
     }
+
+    private class TargetFrameworksTheoryData : TheoryData<string>
+    {
+        public TargetFrameworksTheoryData()
+        {
+            var csproj = Path.Combine(GetSourceDirectory(), Path.Combine("..", "..", "Src", "FluentAssertions", "FluentAssertions.csproj"));
+            var project = XDocument.Load(csproj);
+            var targetFrameworks = project.XPathSelectElement("/Project/PropertyGroup/TargetFrameworks");
+            foreach (string targetFramework in targetFrameworks!.Value.Split(';'))
+            {
+                Add(targetFramework);
+            }
+        }
+    }
 }