How to access fields of a TTestCase in a TTestSetup class

Question

I am creating unit tests with DUnit. I have a class that takes quite a long time to initialize.

I derive a class TMyTestSetup from TTestSetup and override its Setup method. This SetUp method is only called once for all the tests in my TTestCase. I put the Initialization process in the TMyTestSetup.SetUp routine to increase performance.

My problem is how can I access the object I want to initialize, which is a field of my TMyTest in the TestSetup class? Is the only way to do it declaring it globally?

untested short example:

TMyTestSetup = class(TTestSetup)
  protected
    procedure SetUp; override;
end;

TMyTest = class(TTestcase)
public
    fTakes4Ever2Init : TInits4Ever2Init;
published
  procedure Test1;     
end;

implementation

procedure TMyTestSetup.Setup;
begin
   // How can I access fTakes4Ever2Init from here?
  fTakes4Ever2Init.create // This is the call that takes long
end;

procedure TMyTest.Test1;
begin
  fTakes4Ever2Init.DoSomething;
end;

initialization
  RegisterTest(TMyTestSetup.Create(TMyTest.Suite));

Answer 1

The trick is to use a public class variable in the TMyTestSetup class.

Like this (tested and working, complete) example:

unit TestTestUnit;

interface

uses
  TestFramework, TestExtensions;

type
  TInits4Ever2Init = class
  private
    FValue: integer;
  public
    constructor Create;
    procedure   DoSomething1;
    procedure   DoSomething2;
    procedure   DoSomething3;
  end;

type
  TMyTestSetup = class(TTestSetup)
  public class var
    fTakes4Ever2Init: TInits4Ever2Init;
  protected
    procedure SetUp; override;
  end;

  TMyTest = class(TTestCase)
  published
    procedure Test1;
    procedure Test2;
    procedure Test3;
  end;

implementation

uses
  SysUtils, Windows;

{ TMyTestSetup }

procedure TMyTestSetup.Setup;
begin
  fTakes4Ever2Init := TInits4Ever2Init.create; // This is the call that takes long
end;

{ TMyTest }

procedure TMyTest.Test1;
begin
  TMyTestSetup.fTakes4Ever2Init.DoSomething1;
end;

procedure TMyTest.Test2;
begin
  TMyTestSetup.fTakes4Ever2Init.DoSomething2;
end;

procedure TMyTest.Test3;
begin
  TMyTestSetup.fTakes4Ever2Init.DoSomething3;
end;

{ TInits4Ever2Init }

constructor TInits4Ever2Init.Create;
begin
  inherited Create;

  // FValue and Format('%p, %d', [Pointer(Self), FValue])) are to confirm
  //   that we are talking to the same object for all the tests,
  //   but that the object is different each time we run the test suite.

  Randomize;
  FValue := Random(10000);

  OutputDebugString(pAnsiChar('-- TInits4Ever2Init.Create: '
    + Format('%p, %d', [Pointer(Self), FValue])));
end;

procedure TInits4Ever2Init.DoSomething1;
begin
  OutputDebugString(pAnsiChar('-- TInits4Ever2Init.DoSomething1: '
    + Format('%p, %d', [Pointer(Self), FValue])));
end;

procedure TInits4Ever2Init.DoSomething2;
begin
  OutputDebugString(pAnsiChar('-- TInits4Ever2Init.DoSomething2: '
    + Format('%p, %d', [Pointer(Self), FValue])));
end;

procedure TInits4Ever2Init.DoSomething3;
begin
  OutputDebugString(pAnsiChar('-- TInits4Ever2Init.DoSomething3: '
    + Format('%p, %d', [Pointer(Self), FValue])));
end;

initialization
  RegisterTest(TMyTestSetup.Create(TMyTest.Suite));
end.

As the comments in the sample indicate, I have used a randomised private variable, and some debug trace output, to confirm that each test call with the test suite is to the same copy of the target object, but that we are getting a different copy of the target object each time the test suite is run.

Answer 2

You can derive a new Test Suite class from TTestSuite class, and override its SetUp and TearDown methods, then you can add your test cases to this particular test suite, and register the suite.

This way, Setup and TearDown methods of your test suite class will be called once, and SetUp and TearDown methods of each test case will be called for every test method defined in that test case.

Execution order will be like this:

TestSuite.SetUp;

-- TestCase1.Setup;
---- TestCase1.Test1;
-- TestCase1.TearDown;
-- TestCase1.Setup;
---- TestCase1.Test2;
-- TestCase1.TearDown;

-- TestCase2.Setup;
---- TestCase2.Test1;
-- TestCase2.TearDown;
-- TestCase2.Setup;
---- TestCase2.Test2;
-- TestCase2.TearDown;

-- TestCaseN.Setup;
---- TestCaseN.Test1;
-- TestCaseN.TearDown;
-- TestCaseN.Setup;
---- TestCaseN.Test2;
-- TestCaseN.TearDown;

TestSuite.TearDown;

Answer 3

Having just one published method, which in turn call all your other test methods is the lazy but quicker way of having the Setup and TearDown procedure called only once.

Answer 4

You can't initialize TTestCase fields for a whole test suite, and here is an explanation why:

unit Tests3;

interface

uses
  TestFramework, TestExtensions, Windows, Forms, Dialogs, Controls, Classes,
  SysUtils, Variants, Graphics, Messages;

type
  TMyTestCase = class(TTestCase)
  private
    FValue: Integer;
  published
    procedure Test1;
    procedure Test2;
  end;

implementation

{ TMyTestCase }

procedure TMyTestCase.Test1;
begin
  FValue:= 99;
  ShowMessage(Format('%p, %d', [Pointer(Self), FValue]));
end;

procedure TMyTestCase.Test2;
begin
  ShowMessage(Format('%p, %d', [Pointer(Self), FValue]));
end;

initialization
  RegisterTest(TMyTestCase.Suite);
end.

If you run the above unit test you will see that the 'Self' addresses shown in Test1 and Test2 methods are different. That means that TMyTestCase object instances are different for Test1 and Test2 calls.

Consequently, any fields you may declare in TMyTestCase class are volatile between test method's calls.

To perform "global" initialization you should declare your object globally, not as TMyTestCase field.