public void Persist_RetainsSemVer2Version() { // Arrange var fileSystem = new Mock <IFileSystem>(); fileSystem .Setup(x => x.FileExists(CacheFileName)) .Returns(false); var memoryStream = new MemoryStream(); fileSystem .Setup(x => x.CreateFile(CacheFileName)) .Returns(memoryStream); var actual = new ServerPackageStore(fileSystem.Object, CacheFileName); actual.Store(new ServerPackage { Id = PackageId, Version = SemVer2Version }); // Act actual.Persist(); // Assert var content = Encoding.UTF8.GetString(memoryStream.ToArray()); Assert.Contains(SemVer2VersionString, content); }