Understanding the concept of a Stub with an example

Question

I recently received some feedback about some tests we wrote a long time ago from a contractor for a legacy application. I am confused with the terminology that he used and I won't get chance to talk to him again for another month (when I will speak to him). Please see the code below:

 [TestMethod]
        public void Is_Correct_Months()
        {
            IService service = new Service();

            DataTable t1 = service.GetMonths();
            DataTable t2 = BuildExpectedTable();

            Assert.IsNotNull(t1);
            Assert.AreEqual(t1.Rows.Count, t2.Rows.Count);

            for (int i = 0; i <= 2; i++)
            {
                Assert.AreEqual(t1.Rows[i][0], t2.Rows[i][0]);
                Assert.AreEqual(t1.Rows[i][1], t2.Rows[i][1]);
            }
        }

        public DataTable BuildExpectedTable()
        {
            DataTable dt = new DataTable();
            //Add column names to datatable
            dt.Columns.Add("Column1", typeof(string));
            dt.Rows.Add("January");
            dt.Rows.Add("May");
            dt.Rows.Add("December");
            return dt;
        }

Question: Is the BuildExpectedTable method a Stub or not in this case? Is it a bad idea to Assert against BuildExpectedTable (as I have done)?

Now see the code below:

 var mockCalculator = new Moq.Mock<ICalculator>();
            mockChangeCalculator.SetupProperty(client => client.Number1, 400).SetupProperty(client => client.Number2, 200);

This is obviously a mock. Question: Could it ever be construed as a Stub?

Now see the code below:

int[] values = new int[] { 1, 3, 5, 9 };
 
    IEnumerable<int> processed = ProcessInput(values);
 
    int[] expected = new int[] { 1, 9, 25, 81 };
    CollectionAssert.AreEqual(expected, processed);

Question: Is expected a stub in this case?

Update

[TestMethod]
            public void Is_Correct_Months()
            {
                IService service = new Service();

                DataTable t1 = service.GetMonths();

                DataTable dt2 = new DataTable();
                //Add column names to datatable
                dt.Columns.Add("Column1", typeof(string));
                dt.Rows.Add("January");
                dt.Rows.Add("May");
                dt.Rows.Add("December");

                Assert.IsNotNull(t1);
                Assert.AreEqual(t1.Rows.Count, t2.Rows.Count);

                for (int i = 0; i <= 2; i++)
                {
                    Assert.AreEqual(t1.Rows[i][0], t2.Rows[i][0]);
                    Assert.AreEqual(t1.Rows[i][1], t2.Rows[i][1]);
                }
            }