add custom output test

test/TensorFlowNET.Keras.UnitTest/OutputTest.cs

@@ -0,0 +1,55 @@
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using static Tensorflow.Binding;
+using static Tensorflow.KerasApi;
+using Tensorflow.Keras;
+
+namespace Tensorflow.Keras.UnitTest
+{
+    [TestClass]
+    public class OutputTest
+    {
+        [TestMethod]
+        public void OutputRedirectTest()
+        {
+            using var newOutput = new System.IO.StringWriter();
+            tf_output_redirect = newOutput;
+            var model = keras.Sequential();
+            model.add(keras.Input(shape: 16));
+            model.summary();
+            string output = newOutput.ToString();
+            Assert.IsTrue(output.StartsWith("Model: sequential"));
+            tf_output_redirect = null; // don't forget to change it to null !!!!
+        }
+
+        [TestMethod]
+        public void SwitchOutputsTest()
+        {
+            using var newOutput = new System.IO.StringWriter();
+            var model = keras.Sequential();
+            model.add(keras.Input(shape: 16));
+            model.summary(); // Console.Out
+
+            tf_output_redirect = newOutput; // change to the custom one
+            model.summary();
+            string firstOutput = newOutput.ToString();
+            Assert.IsTrue(firstOutput.StartsWith("Model: sequential"));
+
+            // if tf_output_reditect is StringWriter, calling "set" will make the writer clear.
+            tf_output_redirect = null; // null means Console.Out
+            model.summary();
+
+            tf_output_redirect = newOutput; // again, to test whether the newOutput is clear.
+            model.summary();
+            string secondOutput = newOutput.ToString();
+            Assert.IsTrue(secondOutput.StartsWith("Model: sequential"));
+
+            Assert.IsTrue(firstOutput == secondOutput);
+            tf_output_redirect = null; // don't forget to change it to null !!!!
+        }
+    }
+}