c# - Mocking OpenXML with Moq -

how should test following getworksheetpart method:

public class exceldocument : iexceldocument {     private readonly string _filepath;      public exceldocument(string filepath)     {         _filepath = filepath;     }      public worksheetpart getworksheetpart(ispreadsheetdocument exceldoc, string sheetname)     {         sheet sheet = exceldoc.getsheet(sheetname);         if (sheet == null)         {             throw new argumentexception(                 string.format("no sheet named {0} found in spreadsheet {1}",                     sheetname, _filepath), "sheetname");         }         return exceldoc.getpartbyid(sheet.id);     } } 

where iexceldocument , wrapper's spreadsheetdocumentwrapper interfaces are:

public interface iexceldocument {     worksheetpart getworksheetpart(ispreadsheetdocument exceldoc, string sheetname); }  public interface ispreadsheetdocument {     sheet getsheet(string name);      worksheetpart getpartbyid(string id); } 

here wrapper itself.

public class spreadsheetdocumentwrapper : ispreadsheetdocument {     private spreadsheetdocument exceldoc;      public spreadsheetdocumentwrapper(spreadsheetdocument exceldoc)     {         this.exceldoc = exceldoc;     }      public sheet getsheet(string sheetname)     {         return exceldoc.workbookpart.workbook.descendants<sheet>()                    .singleordefault(s => s.name == sheetname);     }      public worksheetpart getpartbyid(string id)     {         return (worksheetpart)exceldoc.workbookpart.getpartbyid(id);     } } 

finally, test tried implement getworksheetpart. issue not sure how test functionality. idea worksheetpart given sheet name , spreadsheet document.

public class test {     [testclass()]     public class excelupdatelogictests     {         [testmethod()]         public void excel_getworkseetparttest()         {             mock<ispreadsheetdocument> mockspreadhseet = new mock<ispreadsheetdocument>();             sheet sheet = new sheet();             string id = "1";             sheet.name = "sheet";             sheet.id = id;              mockspreadhseet.setup(doc => doc.getsheet("sheet")).returns(sheet);              mockspreadhseet.setup(doc => doc.getpartbyid(id)).returns(????);              mock<iexceldocument> mockexceldocument = new mock<iexceldocument>();             worksheetpart mockworkseet = mockexceldocument.object                 .getworksheetpart(mockspreadhseet.object, "sheet");              assert.istrue(mockworkseet.getidofpart(mockworkseet) == id);         }     } } 

here general openxml structure tree spreadsheets:

                spreadsheet                       |                           workbookpart                /         |             \    workbook workbookstylespart worksheetpart          |          |               |     sheets     stylesheet        worksheet         |                        /        \          (refers               sheetdata        columns      worksheetparts)            |                                 rows 

since exceldocument system under test there no need mock iexceldocument. should mock/stub/fake dependencies needed test sut

now able test pass this...

public class test {     [testclass()]     public class excelupdatelogictests {         [testmethod()]         public void given_sheetname_exceldocument_should_getworkseetpart() {             //arrange             var stream = new memorystream();//avoid having use actual file on disk             var spreadsheetdocument = spreadsheetdocument.create(stream, spreadsheetdocumenttype.workbook);              // add workbookpart.             workbookpart workbookpart = spreadsheetdocument.addworkbookpart();             workbookpart.workbook = new workbook();              // add worksheetpart.             worksheetpart worksheetpart = workbookpart.addnewpart<worksheetpart>();             worksheetpart.worksheet = new worksheet(new sheetdata());              // add sheets list.             sheets sheets = spreadsheetdocument.workbookpart.workbook.appendchild<sheets>(new sheets());              // append new worksheet , associate workbook.             string expectedid = workbookpart.getidofpart(worksheetpart);             string sheetname = "mysheet";              sheet sheet = new sheet() {                 id = expectedid,                 sheetid = 1,                 name = sheetname             };             sheets.append(sheet);              var wrapper = new spreadsheetdocumentwrapper(spreadsheetdocument);              string fakefilepath = "path";             var sut = new exceldocument(fakefilepath);              //act             worksheetpart result = sut.getworksheetpart(wrapper, sheetname);              //assert             assert.isnotnull(result);             var actualid = workbookpart.getidofpart(result);             assert.areequal(expectedid, actualid);         }     } } 

the process of doing raised questions current design.

if whole point of creating abstraction hide implementation details , reduce tight coupling on external framework make things easier mock , test having create actual spreadsheetdocument , wrapping test seems redundant.

a lot of parts of framework difficult mock given internal generation. hide behind other abstractions, given not know enough end goal of system cannot advise design structure should taking.