UnitTest.cs

void Should_Insert_Entity()
{
    // Arrange
    var entity = new Account
    {
        Id = "1",
        Name = "first_Account",
        IsActive = true,
        CreatedOn = DateTime.UtcNow
    };
            
    // Act
    var result = _repository.Insert(entity);
                        
    // Assert
    var accounts = _repository.GetMany(x => true);   
    accounts.Count.Should()
    .Be(1);
}