Added comment and test

Signed-off-by: Emmanuel Bigeon <emmanuel@bigeon.fr>

gclc/src/test/java/net/bigeon/gclc/command/base/EchoCommandTest.java

@@ -0,0 +1,44 @@
+package net.bigeon.gclc.command.base;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.fail;
+
+import java.io.IOException;
+
+import org.junit.Test;
+
+import net.bigeon.gclc.exception.CommandRunException;
+import net.bigeon.gclc.utils.PipedConsoleOutput;
+
+public class EchoCommandTest {
+
+    @Test
+    public void testExecute() throws IOException, CommandRunException {
+        final EchoCommand echo = new EchoCommand("echo");
+        assertNotNull("Help tip should be specified", echo.tip());
+        assertNotNull("Usage should be specified", echo.usageDetail());
+
+        try (PipedConsoleOutput out = new PipedConsoleOutput()) {
+            echo.execute(out, null);
+            assertEquals("Echo should print a line", "", out.readNextLine());
+
+            echo.execute(out, null, "Message");
+            assertEquals("Echo should print argument", "Message", out.readNextLine());
+
+            echo.execute(out, null, "Message {0}", "with parameter");
+            assertEquals("Echo should format string and print", "Message with parameter",
+                    out.readNextLine());
+        }
+
+        final PipedConsoleOutput out = new PipedConsoleOutput();
+        out.close();
+        try {
+            echo.execute(out, null);
+            fail("Should not be able to print in closed outputs");
+        } catch (final CommandRunException e) {
+            // expected
+        }
+    }
+
+}