add partial class test

InterfaceGenerator.Tests/PartialClassTests.cs

@@ -0,0 +1,16 @@
+using System;
+using FluentAssertions;
+using InterfaceGenerator.Tests.Partial;
+using Xunit;
+
+namespace InterfaceGenerator.Tests;
+
+public class PartialClassTests
+{
+    [Fact]
+    public void GeneratesMethodFromOtherParts()
+    {
+        var tInterface = typeof(IPartialClass);
+        tInterface.GetMethods().Should().Contain(x => x.Name == nameof(PartialClass.SomeMethodThatShouldGenerate));
+    }
+}