Nunit Test Dependent Commits - By ID

Question

I have a method that does two commits - here is a simplified version of it:

    public void methodA(objectA objA, List<objectB> objB) 
    {
         _repoA.AddAsync(objA);
         var id = _repoA.SaveChanges();
         if(id > 0) {
            foreach (var ob in objB)
            {
              ob.objAId = id;
              _repoB.AddRange(ob);
            }
           _repoB.SaveChanges();
         }
   }

How do I get/set the id in my unit test to see if my list's objAId is set and that it actually contains two object - right now as I cannot set/get id in first commit my test fails:

[Fact]
    public async void test()
    {
        var objA = new ObjA(null);
        var objB = new List<ObjB>
        {
           new ObjB(null, null, "Test"),
           new ObjB(null, null, "Test2")
        });

        var result = await _sut.methodA(objA, objB);

        Assert.NotNull(result);
        _mockFieldRepository.Verify(x => x.InsertAsync(It.IsAny<MyObjectA>()), Times.Once);
        _mockFieldOptionRepository.Verify(x => x.InsertAsync(It.IsAny<MyObjectB>()), Times.Once); //fails here
        _mockFieldOptionRepository.Verify(x => x.InsertAsync(It.Is<MyObjectB>(p => p.Id > 0 && p.objAId == objA.Id))); //fails here

    }