Mixing Assert and Act in AAA unit testing syntax

Is it OK to mix Assert and Act steps? Is AAA more of a guideline than a rule? Or am I missing something?

Here is my test:

[TestMethod]
public void CancelButtonSelected_DontCancelTwiceThenCancel_DialogCloses()
{
    // Arrange
    IAddAddressForm form = Substitute.For<IAddAddressForm>();
    // Indicate that when Show CancelMessage is called it 
    //  should return cancel twice (saying we want to cancel the cancel)
    //  then it should return ok
    form.ShowCancelMessage().Returns(DialogResult.Cancel, 
         DialogResult.Cancel, DialogResult.OK);

    AddAddressController controller = new AddAddressController(form);
    AddressItem item = TestHelper.CreateAddressBob();

    // Act
    EnterAddressInfo(form, controller, item);
    controller.CancelButtonSelected();
    Assert.IsTrue(form.DialogResult == DialogResult.None);

    controller.CancelButtonSelected();
    Assert.IsTrue(form.DialogResult == DialogResult.None);

    controller开发者_如何学编程.CancelButtonSelected();

    // Assert
    Assert.IsTrue(form.DialogResult == DialogResult.Cancel);
}

So I call a method 3 times. After each call, I want to make sure that we did not really cancel the dialog. Then on the third call, the dialog should be canceled.

Is this "legal" use of AAA syntax/styling?

AAA is a guideline to make your unit tests more readable. In the example you provided I would argue you have not achieved that goal.

I think the following tests make the scenario you are testing more readable.

[TestMethod]
public void CancelButtonSelected_ShouldSetDialogResultToNone_WhenFirstCancelButtonIsSelected()
{
    // Arrange
    IAddAddressForm form = ArrangeFormForCancelButtonSelectedTests();
    AddAddressController controller = ArrangeControllerForCancelButtonSelectedTests();

    // Act
    controller.CancelButtonSelected();

    // Assert
    Assert.IsTrue(form.DialogResult == DialogResult.None);
}

[TestMethod]
public void CancelButtonSelected_ShouldSetDialogResultToNone_WhenSecondCancelButtonIsSelected()
{
    // Arrange
    IAddAddressForm form = ArrangeFormForCancelButtonSelectedTests();
    AddAddressController controller = ArrangeControllerForCancelButtonSelectedTests();

    // Act
    controller.CancelButtonSelected();
    controller.CancelButtonSelected();

    // Assert
    Assert.IsTrue(form.DialogResult == DialogResult.None);

}

[TestMethod]
public void CancelButtonSelected_ShouldSetDialogResultToCancel_WhenThirdCancelButtonIsSelected()
{
    // Arrange
    IAddAddressForm form = ArrangeFormForCancelButtonSelectedTests();
    AddAddressController controller = ArrangeControllerForCancelButtonSelectedTests();

    // Act
    controller.CancelButtonSelected();
    controller.CancelButtonSelected();
    controller.CancelButtonSelected();

    // Assert
    Assert.IsTrue(form.DialogResult == DialogResult.Cancel);
}

AAA is just a guideline to make your unit tests more readable. It is perfectly OK to deviate if you have a good reason to do so. You used whitespaces and comments to separate the different phases in code to some extent, which is good. In such cases it may also be helpful to add comments explaining the story you are testing.