public void WithDirectives() { /* Given */ EnumDefinition original = @"enum ENUM { V1, V2 }"; /* When */ var modified = original .WithDirectives(new List <Directive> { "@a" }); /* Then */ Assert.Null(original.Directives); Assert.NotNull(modified.Directives); var a = Assert.Single(modified.Directives); Assert.Equal("a", a?.Name); }