Testing console based applications/programs - Java

Question

All,

I have written a PhoneBook application in Java that is command line based. The application basically asks for some details of user like Name, Age, Address and p

Answer 1

This takes a basic looping console application and makes it testable, using the ideas from oxbow_lakes' answer.

The class-proper:

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintStream;

public class TestableLoopingConsoleExample {

   public static final String INPUT_LINE_PREFIX = "> ";
   public static final String EXIT_COMMAND = "exit";
   public static final String RESPONSE_PLACEHOLDER = "...response goes here...";
   public static final String EXIT_RESPONSE = "Exiting.";

   public static void main(String[] cmdLineParams_ignored) throws IOException {
      BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
      PrintStream out = new PrintStream(System.out);
      PrintStream err = new PrintStream(System.err);

      try {
         new TestableLoopingConsoleExample().main(cmdLineParams_ignored, in, out);
      } catch (Exception e) {  //For real use, catch only the exactly expected types
         err.println(e.toString());
      }
   }

...continued...

   public void main(String[] cmdLineParams_ignored, BufferedReader in, PrintStream out)
         throws IOException {

      System.out.println("Enter some text, or '" + EXIT_COMMAND + "' to quit");

      while (true) {

         out.print(INPUT_LINE_PREFIX);
         String input = in.readLine();
         out.println(input);

         if (input.length() == EXIT_COMMAND.length() &&
            input.toLowerCase().equals(EXIT_COMMAND)) {

            out.println(EXIT_RESPONSE);
            return;
         }

         out.println(RESPONSE_PLACEHOLDER);
      }
   }
}

The test (JUnit4):

import static org.junit.Assert.assertEquals;
import static testableloopingconsoleapp.TestableLoopingConsoleExample.EXIT_COMMAND;
import static testableloopingconsoleapp.TestableLoopingConsoleExample.EXIT_RESPONSE;
import static testableloopingconsoleapp.TestableLoopingConsoleExample.INPUT_LINE_PREFIX;
import static testableloopingconsoleapp.TestableLoopingConsoleExample.RESPONSE_PLACEHOLDER; 

import org.junit.Before;
import org.junit.Test; 

import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.PrintStream;
import java.io.StringReader; 

public class TestableLoopingConsoleExampleTest { 

  private final ByteArrayOutputStream out = new ByteArrayOutputStream();
  private final ByteArrayOutputStream err = new ByteArrayOutputStream(); 

  @Before
  public final void resetOutputStreams() {
     out.reset();
     err.reset();
  } 

...continued...

  @Test
  public void testableMain_validInputFromString_outputAsExpected() throws Exception {
     String line1 = "input line 1\n";
     String line2 = "input line 2\n";
     String line3 = "input line 3\n";
     String exitLine = EXIT_COMMAND + "\n"; 

     BufferedReader in = new BufferedReader(new StringReader(
         line1 + line2 + line3 + exitLine
     ));
     String expectedOutput =
         INPUT_LINE_PREFIX + line1 +
         RESPONSE_PLACEHOLDER + "\n" +
         INPUT_LINE_PREFIX + line2 +
         RESPONSE_PLACEHOLDER + "\n" +
         INPUT_LINE_PREFIX + line3 +
         RESPONSE_PLACEHOLDER + "\n" +
         INPUT_LINE_PREFIX + exitLine +
         EXIT_RESPONSE + "\n"; 

     String[] ignoredCommandLineParams = null; 

     new TestableLoopingConsoleExample().main(ignoredCommandLineParams, in, new PrintStream(out)); 

     assertEquals(expectedOutput, out.toString());
  } 

}