Providing data to Mock for Unit Testing

Question

The class I am doing Unit Testing scrolls each record of a DB table and sum the value in a field to the previous value. The following is the class reduced to the bone:

procedure TSumList.Sum;
var
  FSum:integer;
begin
  FSum:=0;
  FDB.First;
  while not FDB.EOF do
  begin
    FSum:=FSum+FDB.GetAmount;
    FDB.Next;
  end;
end;

FDB refers to the DB mock interface named IIDBTable.

The following is the DB mock for the dependency injection:

  IIDBTable = interface
    ['{A299D1D6-93AF-45CC-8DE2-9A4EE188C352}']
    procedure First;
    procedure Next;
    function EOF : boolean;
    function GetAmount:integer;
  end;

  TMockDBTable = class (TInterfacedObject,IDBTable)
    procedure First;
    procedure Next;
    function EOF : boolean;
    function GetAmount:integer;
  end;

Problem is I don't know how to provide data to the mock for the test. Of course I can add an extra procedure, say AddValues(aAmount:integer), that does the job but in that case I would end up with this extra procedure in production too and I don't need it.

What is the best practice for this ?

I use Spring for Delphi framework

Answer 1

You can also use DSharp mocks (or Delphi Mocks).

This will be the setup code for DSharp (Delphi Mocks should be similar)

var
  mockDBTable: Mock<IIDBTable>;
begin
  mockDBTable.Setup.WillExecute.Once.WhenCalling.First;
  mockDBTable.Setup.WillReturn(False).Exactly(5).WhenCalling.EOF;
  mockDBTable.Setup.WillReturn(True).Once.WhenCalling.EOF;
  mockDBTable.Setup.WillReturn(5).Once.WhenCalling.GetAmount;
  mockDBTable.Setup.WillReturn(4).Once.WhenCalling.GetAmount;
  mockDBTable.Setup.WillReturn(3).Once.WhenCalling.GetAmount;
  mockDBTable.Setup.WillReturn(2).Once.WhenCalling.GetAmount;
  mockDBTable.Setup.WillReturn(1).Once.WhenCalling.GetAmount;
  mockDBTable.Setup.WillExecute.Exactly(5).WhenCalling.Next;

What you do here is specify what you expect to be called and what to be returned. This saves you from manually writing a mock class and feed it with data.