Add JUnit tests for Ui class and some methods in Parser class

src/test/java/parser/ParserTest.java

@@ -0,0 +1,29 @@
+package parser;
+
+import org.junit.Test;
+
+import java.io.ByteArrayInputStream;
+
+import static org.junit.Assert.assertEquals;
+
+public class ParserTest {
+    @Test
+    public void detectExitCommand_exitCommand_true() {
+        String exitCommand = "bye";
+        System.setIn(new ByteArrayInputStream(exitCommand.getBytes()));
+        boolean isExitCommand = new Parser().detectExitCommand(exitCommand);
+
+        assertEquals(true, isExitCommand);
+        System.setIn(System.in);
+    }
+
+    @Test
+    public void detectExitCommand_nonExitCommand_false() {
+        String nonExitCommand = "hey";
+        System.setIn(new ByteArrayInputStream(nonExitCommand.getBytes()));
+        boolean isExitCommand = new Parser().detectExitCommand(nonExitCommand);
+
+        assertEquals(false, isExitCommand);
+        System.setIn(System.in);
+    }
+}

src/test/java/stub/message/MessageStub.java

@@ -0,0 +1,9 @@
+package stub.message;
+
+import ui.message.Message;
+
+public class MessageStub extends Message {
+    public MessageStub() {
+        super("hello", ":)");
+    }
+}

src/test/java/ui/UiTest.java

@@ -0,0 +1,76 @@
+package ui;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import stub.message.MessageStub;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
+
+import static org.junit.Assert.assertEquals;
+
+public class UiTest {
+    private final ByteArrayOutputStream outContent = new ByteArrayOutputStream();
+    private final ByteArrayOutputStream errContent = new ByteArrayOutputStream();
+    private final PrintStream originalOut = System.out;
+    private final PrintStream originalErr = System.err;
+
+    @Before
+    public void setUpStreams() {
+        System.setOut(new PrintStream(outContent));
+        System.setErr(new PrintStream(errContent));
+    }
+
+    @After
+    public void restoreStreams() {
+        System.setOut(originalOut);
+        System.setErr(originalErr);
+    }
+
+    @Test
+    public void testShowWelcome() {
+        new Ui().showWelcome();
+
+        assertEquals(
+                "\t_________________________________________________\n" +
+                "\tHello! I'm Duke, what shall we do today? ٩(｡•́‿•̀｡)۶\n" +
+                "\t_________________________________________________\n",
+                outContent.toString()
+                );
+    }
+
+    @Test
+    public void testShowGoodbye() {
+        new Ui().showGoodbye();
+
+        assertEquals(
+                "\t_________________________________________________\n" +
+                        "\tBye, see you again ヾ(=´･∀･｀=)\n" +
+                        "\t_________________________________________________\n",
+                outContent.toString()
+        );
+    }
+
+    @Test
+    public void testShowMessage() {
+        new Ui().showMessage(new MessageStub());
+
+        assertEquals("\t_________________________________________________\n" +
+                "\thello :)\n" +
+                "\t_________________________________________________\n",
+                outContent.toString()
+                );
+    }
+
+    @Test
+    public void testReadInputMessage() {
+        String inputMessage = "how are you";
+        System.setIn(new ByteArrayInputStream(inputMessage.getBytes()));
+        String inputReadByUi = new Ui().readInputMessage();
+
+        assertEquals(inputMessage, inputReadByUi);
+        System.setIn(System.in);
+    }
+}