Building Maintainable Software, Java Edition

Chapter 10. Automate Tests

Keep the bar green to keep the code clean.

The jUnit motto

Guideline:

• Automate tests for your codebase.

• Do this by writing automated tests using a test framework.

• This improves maintainability because automated testing makes development predictable and less risky.

In Chapter 4, we have presented isValid, a method to check whether bank account numbers comply with a checksum. That method contains a small algorithm that implements the checksum. It is easy to make mistakes in a method like this. That is why probably every programmer in the world at some point has written a little, one-off program to test the behavior of such a method, like so:

package eu.sig.training.ch10;

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

import eu.sig.training.ch04.v1.Accounts;

public class Program {
    public static void main(String[] args) throws IOException {
        BufferedReader isr =
            new BufferedReader(new InputStreamReader(System.in));
        String acct;
        do {
            System.out.println("Type a bank account number on the next line.");
            acct = isr.readLine();
            System.out.println("Bank account number '" + acct + "' is" +
                (Accounts.isValid(acct) ? "" : " not") + " valid.");
        } while (acct != null && acct.length() != 0);
    }
}

This is a Java class with a main method, so it can be run from the command line:

$ java Program Type a bank account number on the next line. 123456789 Bank account number '123456789' is valid. Type a bank account number ...