public void WriteResults_Should_WriteAnEntry_When_NoFileExists() { var streamFactory = new Mock<IStreamFactory>(); var memoryStream = new TestStreamContents(); streamFactory.Setup(s => s.GetStream("c:\\dir\\testname.json")).Returns(memoryStream); var target = new OutputWriter("c:\\dir", streamFactory.Object); target.WriteResults("testname", "label", 42); Assert.AreEqual(@"{ ""benchmarkname"": ""testname"", ""data"": [[""label"", 42]] }", memoryStream.Contents); }