title: Mock.Arrange what does it actually do?
body: <p>I am new to testing and new to JustMock.</p>
  <p>I have written my first test.</p>
  <pre><code>    [TestMethod]
      public void CheckifExportToCSVIsSuccessfull()
      {
          C1FlexGrid c1flexGrid = new C1FlexGrid();
          
          C1FlexGridBase c1flexGridBase = (C1FlexGridBase)(c1flexGrid);
  
          Timeslice.ComponentOneExtensions.C1FlexGridExtensions.ExportResult expected = Timeslice.ComponentOneExtensions.C1FlexGridExtensions.ExportResult.Succeeded;
  
          Mock.Arrange(() =&gt; c1flexGridBase.ExportToCSV($&quot;&quot;)).Returns(Timeslice.ComponentOneExtensions.C1FlexGridExtensions.ExportResult.Failed);
  
          // Assert 
          Assert.AreEqual(expected, c1flexGridBase.ExportToCSV($&quot;&quot;));
      }
  </code></pre>
  <p>Here is the function it is testing.</p>
  <pre><code>     public static ExportResult ExportToCSV(this C1FlexGridBase c1FlexGrid, string fileName)
      {
          c1FlexGrid.SaveGrid(fileName, FileFormatEnum.TextComma, FileFlags.IncludeFixedCells);
          return ExportResult.Succeeded;
      }
  </code></pre>
  <p>The test works as it is failing.</p>
  <p>I don't understand what the Arrange is supposed to do.</p>