Add Spreadsheet tests

Tests for `fromFile` (does not work atm. => WIP), `tryGetSharedStringTable`, and `getWorkbookPart`.

tests/FsSpreadsheet.ExcelIO.Tests/Spreadsheet.fs

@@ -1,2 +1,61 @@
 module Spreadsheet
 
+open Expecto
+open FsSpreadsheet.ExcelIO
+open DocumentFormat.OpenXml
+
+
+//let testFilePath = @"C:\Repos\CSBiology\FsSpreadsheet\tests\FsSpreadsheet.ExcelIO.Tests\data\testUnit.xlsx"
+let testFilePath = System.IO.Path.Combine(__SOURCE_DIRECTORY__, "data", "testUnit.xlsx")
+// *fox = from OpenXml, to distinguish between objects from FsSpreadsheet.ExcelIO
+let ssdFox = Packaging.SpreadsheetDocument.Open(testFilePath, false)
+let wbpFox = ssdFox.WorkbookPart
+let sstpFox = wbpFox.SharedStringTablePart
+let sstFox = sstpFox.SharedStringTable
+let sstFoxInnerText = sstFox.InnerText
+
+
+//let testSsdFox2 = Packaging.SpreadsheetDocument.Open(testFilePath, false)
+
+//let testDoc = Spreadsheet.fromFile testFilePath false
+
+//testSsdFox = testDoc
+//testSsdFox = testSsdFox2
+
+
+
+[<Tests>]
+let spreadsheetTests =
+    testList "Spreadsheet" [
+        // is it even possible to test this?
+        //testList "fromFile" [
+            //testCase "is equal to testSsd" <| fun _ ->
+            //    let ssd = Spreadsheet.fromFile testFilePath false
+            //    Expect.equal testDoc ssdFox "Both testFiles differ"
+            //    testSsd.Close()
+        //]
+        testList "tryGetSharedStringTable" [
+            let sst = Spreadsheet.tryGetSharedStringTable ssdFox
+            testCase "is Some" <| fun _ ->
+                Expect.isSome sst "Is None"
+            testCase "is equal to testSstFox" <| fun _ ->
+                Expect.equal sst.Value sstFox "Differs"
+            testCase "inner text is correct" <| fun _ ->
+                Expect.equal sst.Value.InnerText sstFoxInnerText "Differs"
+        ]
+        testList "getWorkbookPart" [
+            let wbp = Spreadsheet.getWorkbookPart ssdFox
+            testCase "is equal to wbpFox" <| fun _ ->
+                Expect.equal wbp wbpFox "Differs"
+        ]
+    ]
+
+
+
+
+
+
+
+
+
+//testSsdFox.Close()