Delphi Unit Testing : Writing a simple spy for the CUT

Question

I'm searching for a way to easily and concisely write a spy for the DUnitX testing framework under Delphi.

In the past, I've used very ugly ways of doing that using :

[TestFixture]
Test = class(TObject)
public
  [test]
  procedure Test1;
end;

TMyClass = class(TObject)
protected
  procedure MyProcedure; virtual;
end;

TMyTestClass = class(TMyClass)
protected
  fMyProcedureCalled : Boolean;
  procedure MyProcedure; override;
end

procedure TMyTestClass.MyProcedure;
begin
   fMyProcedureCalled := true;
   inherited;
end;

procedure Test.Test1;
var aObj : TMyTestClass;
begin
   TMyTestClass.Create;
   Assert.IsTrue(aObj.fMyProcedureCalled);
end;

All of this code to check if a procedure was called. That's too verbose!

Is there a way to write a spy that would help me reduce that code?

Answer 1

Sounds like a use case for a mock (I am using the term mock here because most frameworks refer to their various kinds of test doubles as mock)

In the following example I am using DUnit but it should not make any difference for DUnitX. I am also using the mocking feature from Spring4D 1.2 (I did not check if Delphi Mocks supports this)

unit MyClass;

interface

type
  TMyClass = class
  private
    fCounter: Integer;
  protected
    procedure MyProcedure; virtual;
  public
    property Counter: Integer read fCounter;
  end;

implementation

procedure TMyClass.MyProcedure;
begin
  Inc(fCounter);
end;

end.

program Tests;

uses
  TestFramework,
  TestInsight.DUnit,
  Spring.Mocking,
  MyClass in 'MyClass.pas';

type
  TMyClass = class(MyClass.TMyClass)
  public
    // just to make it accessible for the test
    procedure MyProcedure; override;
  end;

  TMyTest = class(TTestCase)
  published
    procedure Test1;
  end;

procedure TMyClass.MyProcedure;
begin
  inherited;
end;

procedure TMyTest.Test1;
var
  // the mock is getting auto initialized on its first use
  // and defaults to TMockBehavior.Dynamic which means it lets all calls happen
  m: Mock<TMyClass>;
  o: TMyClass;
begin
  // set this to true to actually call the "real" method
  m.CallBase := True;
  // do something with o
  o := m;
  o.MyProcedure;

  // check if the expected call actually did happen
  m.Received(Times.Once).MyProcedure;

  // to prove that it actually did call the "real" method
  CheckEquals(1, o.Counter);
end;

begin
  RegisterTest(TMyTest.Suite);
  RunRegisteredTests();
end.

Keep in mind though that this only works for virtual methods.