如何在 Java 中生成 JUnit 测试用例？

Question

I am practising JUnit test cases and currently working on a problem which is as follows:

• To read HTML from any website say " http://www.google.com " ( Candidate can use any API of inbuilt APIs in Java like URLConnection ).
• Print on console the HTML from the URL above and save it to a file ( web-content.txt) in local machine.
• Write JUnit test cases for the above program.

I've successfully achieved first steps but when I am running JUnit Test Case its showing Failure.

ReadFile.java

package com.test;

import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.Reader;
import java.net.HttpURLConnection;
import java.net.URL;

public class ReadFile 
{
    static void display(String input,OutputStream fos)
    {
        try
        {
            URL url = new URL(input);
            HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
            InputStream stream = new BufferedInputStream(urlConnection.getInputStream());
            Reader reader = new InputStreamReader(stream);
            int data=0;
            while((data=reader.read())!=-1)
            {
                System.out.print((char)data);
                fos.write((char)data);
            }
        }
        catch(Exception e)
        {
            System.out.println(e);
        }
    }
    public static void main(String[] args) 
    {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        String input =null;
        FileOutputStream fos =null;
        System.out.println("Please enter any url");
        try
        {
            input = reader.readLine();
            fos = new FileOutputStream("src/web-context.txt");
            display(input,fos);
        }
        catch(Exception e)
        {
            System.out.println(e);
        }
    }
}

ReadFileTest.java

package com.test;

import static org.junit.Assert.*;

import java.io.ByteArrayOutputStream;

import org.junit.Test;

public class ReadFileTest {

    @Test
    public void test() {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        ReadFile.display("http://google.co.in", baos);
        assertTrue(baos.toString().contains("http://google.co.in"));
    }

}

I am getting following error while running JUnit Test in Eclipse:

java.lang.AssertionError java.lang.AssertionError at org.junit.Assert.fail(Assert.java:86) at org.junit.Assert.assertTrue(Assert.java:41) at org.junit.Assert.assertTrue(Assert.java:52) at com.test.ReadFileTest.test(ReadFileTest.java:15) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown

I want that the JUnit Test Case will return true.

Answer 1

What's not working here is :

assertTrue(baos.toString().contains("http://google.co.in"));

and what would work is

assertTrue(baos.toString().contains("google.co.in")); // note the difference

Answer 2

Make something like that:

static String display(String input) {
    try {
        URL url = new URL(input);
        HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
        InputStream stream = new BufferedInputStream(urlConnection.getInputStream());
        Reader reader = new InputStreamReader(stream);
        int data = 0;
        StringBuilder builder = new StringBuilder();
        while ((data = reader.read()) != -1) {
            builder.append((char) data);
        }
        return builder.toString();
    } catch(Exception e) {
        e.printStackTrace();
        return null;
    }
}

I don't know why you use ByteArrayOutputStream

And now for your test case:

@Test
public void test() {
    String data = ReadFile.display("http://google.co.in");
    assertTrue(data != null);
    assertTrue(data.contains("http://google.co.in"));
}