This is how I resolved it.
Just about everything in my add-in runs from the Click method of a button in the UI. I have changed all those Click methods to consist only of a simple, parameterless call.
I then created a new file (Partial Class) called EntryPoint that had lots of very short Friend Subs, each of which was usually one or two calls to parameterised worker functions, so that all the Click methods just called into this file. So, for example, there's a function that opens a standard document and calls a "save as" into our DMS. The function takes a parameter of which document to open, and there are a couple of dozen standard documents that we use.
So I have
Private Sub btnMemo_Click(ByVal Ctrl As Microsoft.Office.Core.CommandBarButton, ByRef CancelDefault As Boolean) Handles btnMemo.Click
DocMemo()
End Sub
in the ThisAddin and then
Friend Sub DocMemo()
OpenDocByNumber("Prec", 8862, 1)
End Sub
in my new EntryPoints file.
I add a new AddInUtilities file which has
Public Interface IAddInUtilities
#If DEBUG Then
Sub DocMemo()
#End If
End Interface
Public Class AddInUtilities
Implements IAddInUtilities
Private Addin as ThisAddIn
#If DEBUG Then
Public Sub DocMemo() Implements IAddInUtilities.DocMemo
Addin.DocMemo()
End Sub
#End If
Friend Sub New(ByRef theAddin as ThisAddIn)
Addin=theAddin
End Sub
End Class
I go to the ThisAddIn file and add in
Private utilities As AddInUtilities
Protected Overrides Function RequestComAddInAutomationService() As Object If utilities Is Nothing Then utilities = New AddInUtilities(Me) End If Return utilities End Function
And now it's possible to test the DocMemo() function in EntryPoints using NUnit, something like this:
Public Class Numbering
Private appWord As Word.Application
Private objMacros As Object
Public Sub LaunchWord()
appWord = New Word.Application
appWord.Visible = True
Dim AddIn As COMAddIn = Nothing
Dim AddInUtilities As IAddInUtilities
For Each tempAddin As COMAddIn In appWord.COMAddIns
If tempAddin.Description = "CobbettsMacrosVsto" Then
AddIn = tempAddin
End If
Next
AddInUtilities = AddIn.Object
objMacros = AddInUtilities.TestObject
End Sub
Public Sub DocMemo()
objMacros.DocMemo()
End Sub
Public Sub TearDown()
appWord.Quit(False)
End Sub
End Class
The only thing you can't then unit test are the actual Click events, because you're calling into EntryPoints in a different way, ie through the RequestComAddInAutomationService interface rather than through the event handlers.
But it works!
