public void TestIfCompanyExistOnAdd() { var mockSet = new Mock <DbSet <Company> >(); var mockContext = new Mock <CompanyDBEntities>(); mockContext.Setup(m => m.Companies).Returns(mockSet.Object); var companyContext = new CompanyDBContext(mockContext.Object); companyContext.AddCompany(new Company() { CompanyId = 1, CompanyName = "Test", Email = "*****@*****.**", LastName = "Testing", PhoneNumber = 123456 }); mockSet.Verify(m => m.Add(It.IsAny <Company>()), Times.Once()); }