Tests for double and decimal CellValue ctors (#906)

* change cellvalue ctors to use CultureInfo.InvariantCulture
* add culture test for double and decimal CellValue ctor

Author: tomjebo

test/DocumentFormat.OpenXml.Tests/Common/CultureHelper.cs

@@ -0,0 +1,29 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Linq;
+using System.Text;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace DocumentFormat.OpenXml.Tests.Common
+{
+    internal readonly struct CultureInfoTester : IDisposable
+    {
+        private readonly CultureInfo _old;
+
+        public CultureInfoTester(string desired)
+        {
+            _old = Thread.CurrentThread.CurrentCulture;
+            Thread.CurrentThread.CurrentCulture = new CultureInfo(desired);
+        }
+
+        public void Dispose()
+        {
+            Thread.CurrentThread.CurrentCulture = _old;
+        }
+    }
+}

test/DocumentFormat.OpenXml.Tests/Spreadsheet/CellValueTests.cs

@@ -2,8 +2,11 @@
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
 using DocumentFormat.OpenXml.Spreadsheet;
+using DocumentFormat.OpenXml.Tests.Common;
 using System;
 using System.Collections.Generic;
+using System.Globalization;
+using System.Threading;
 using Xunit;
 
 namespace DocumentFormat.OpenXml.Tests
@@ -74,6 +77,30 @@ public void CellDoubleTest(double num)
             Assert.Equal(num, result);
         }
 
+        [InlineData("fr-FR")]
+        [InlineData("de-DE")]
+        [InlineData("zh-CH")]
+        [InlineData("ru-RU")]
+        [InlineData("en-US")]
+        [InlineData("tr-TR")]
+        [InlineData("ar-EG")]
+        [InlineData("fa-IR")]
+        [Theory]
+        public void CellDoubleCultureTest(string culture)
+        {
+            // Change current culture
+            using (new CultureInfoTester(culture))
+            {
+                // Set to a double value
+                double num = 103.2;
+                var value = new CellValue(num);
+
+                // Ensure that thread culture is not used.
+                Assert.Equal("103.2", value.Text);
+                Assert.Equal("103.2", value.InnerText);
+            }
+        }
+
         [InlineData("987.6E+30", 9.876E+32)]
         [InlineData("-12.34E-20", -1.234E-19)]
         [Theory]
@@ -180,6 +207,30 @@ public void CellDecimalTestNegative(string input)
             Assert.False(value.TryGetDecimal(out _));
         }
 
+        [InlineData("fr-FR")]
+        [InlineData("de-DE")]
+        [InlineData("zh-CH")]
+        [InlineData("ru-RU")]
+        [InlineData("en-US")]
+        [InlineData("tr-TR")]
+        [InlineData("ar-EG")]
+        [InlineData("fa-IR")]
+        [Theory]
+        public void CellDecimalCultureTest(string culture)
+        {
+            // Change current culture
+            using (new CultureInfoTester(culture))
+            {
+                // Set to a decimal value
+                decimal num = 6049.9M;
+                var value = new CellValue(num);
+
+                // Ensure that thread culture is not used.
+                Assert.Equal("6049.9", value.Text);
+                Assert.Equal("6049.9", value.InnerText);
+            }
+        }
+
         [InlineData("0", false)]
         [InlineData("false", false)]
         [InlineData("1", true)]