Junit-测试不同的类

Question

Hi I'm trying to get my head around Junit testing and I can't find a way to test another class without copy pasting parts of it in. say I want to test this:

import java.io.*;

public class Calculator {

public static void main(String[] args) {
    String s1 = getInput("Enter a numeric value: ");
    String s2 = getInput("Enter a numeric value: ");
    String op = getInput("Enter 1=ADD, 2=Subtract, 3=Multiply, 4=Divide ");

    int opInt = Integer.parseInt(op);
    double result = 0;

    switch (opInt) {
    case 1:
        result = addValues(s1, s2);
        break;
    case 2:
        result = subtractValues(s1, s2);
        break;
    case 3:
        result = multiplyValues(s1, s2);
        break;
    case 4:
        result = divideValues(s1, s2);
        break;

    default:
        System.out.println("You entered an incorrect value");
        return;
    }

    System.out.println("The answer is " + result);

}

private static double divideValues(String s1, String s2) {
    double d1 = Double.parseDouble(s1);
    double d2 = Double.parseDouble(s2);
    double result = d1 / d2;
    return result;
}

private static double multiplyValues(String s1, String s2) {
    double d1 = Double.parseDouble(s1);
    double d2 = Double.parseDouble(s2);
    double result = d1 * d2;
    return result;
}

private static double subtractValues(String s1, String s2) {
    double d1 = Double.parseDouble(s1);
    double d2 = Double.parseDouble(s2);
    double result = d1 - d2;
    return result;
}

private static double addValues(String s1, String s2) {
    double d1 = Double.parseDouble(s1);
    double d2 = Double.parseDouble(s2);
    double result = d1 + d2;
    return result;
}

private static String getInput(String prompt) {
    BufferedReader stdin = new BufferedReader(
            new InputStreamReader(System.in));

    System.out.print(prompt);
    System.out.flush();

    try {
        return stdin.readLine();
    } catch (Exception e) {
        return "error: " + e.getMessage();
    }
}

Is there any way I can set up the JUnit case test to check parts of this without copy and pasting it in for every test or modifying the orginal class. am I missing something or is this something Junit can't do?

Here is what I'm at so far:

import static org.junit.Assert.*;

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

import org.junit.Test;


public class CalculatorTest {

Calculator mycalculator = new Calculator();

@Test
public void test1( ) {
    mycalculator;
    assertEquals(d1 + d2, 20);
}

}

Answer 1

The design of your class doesn't really lend itself to automated testing.

• The only methods in the class are private static, meaning that they can only be accessed from other static methods inside this class (though it is possible to use Reflection to overcome this if you absolutely must have private static members.)
• Parts of the class require user input / intervention, which makes it difficult to test them automatically.
• Your class isn't object-oriented. It is written more like a functional program (eg C), with a main body and global functions, rather than written as an object that provides functionality.

Try something like this instead:

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

public class Calculator {

    // TODO: Move enum to another file
    public static enum OperatorType {
        ADD,
        SUBTRACT,
        MULTIPLY,
        DIVIDE
    }

    public double calculateResult(double operand1, double operand2, OperatorType operator) {
        double result = 0;;
        switch (operator) {
            case ADD:
                result = addValues(operand1, operand2);
                break;
            case DIVIDE:
                result = subtractValues(operand1, operand2);
                break;
            case MULTIPLY:
                result = multiplyValues(operand1, operand2);
                break;
            case SUBTRACT:
                result = subtractValues(operand1, operand2);
                break;
            default:
                break;
        }

        return result;
    }

    public double divideValues(double d1, double d2) {
        double result;
        if (d2 != 0) {
            result = d1 / d2;
        } else {
            // Avoid divide-by-zero error (could also throw it if preferred)
            result = 0;
        }
        return result;
    }

    public double multiplyValues(double d1, double d2) {
        double result = d1 * d2;
        return result;
    }

    public double subtractValues(double d1, double d2) {
        double result = d1 - d2;
        return result;
    }

    public double addValues(double d1, double d2) {
        double result = d1 + d2;
        return result;
    }

    public static void main(String[] args) {
        // Get and validate user input
        String s1 = getInput("Enter a numeric value: ");
        String s2 = getInput("Enter a numeric value: ");
        String op = getInput("Enter 1=ADD, 2=Subtract, 3=Multiply, 4=Divide ");

        // TODO: Handle NumberFormatExceptions here
        double operand1 = Double.parseDouble(s1);
        double operand2 = Double.parseDouble(s2);
        OperatorType operator;

        int opInt = Integer.parseInt(op);
        switch (opInt) {
            case 1:
                operator = OperatorType.ADD;
                break;
            case 2:
                operator = OperatorType.SUBTRACT;
                break;
            case 3:
                operator = OperatorType.MULTIPLY;
                break;
            case 4:
                operator = OperatorType.DIVIDE;
                break;

            default:
                System.out.println("You entered an incorrect value");
                return;
        }

        // Use class to calculate result
        Calculator calculator = new Calculator();
        double result = calculator.calculateResult(operand1, operand2, operator);

        // Output results
        System.out.println("The answer is " + result);
    }

    private static String getInput(String prompt) {
        BufferedReader stdin = new BufferedReader(new InputStreamReader(System.in));

        System.out.print(prompt);
        System.out.flush();

        try {
            return stdin.readLine();
        } catch (Exception e) {
            return "error: " + e.getMessage();
        }
    }
}

• All of your individual mathematical operations are public methods of the Calculator class, which can be tested individually.
• The main mathematical logic, which takes two operands and an operator, is in another public method, which can be tested too.
• User input and output stays in the main method, as it is the logic (not the user input/output) that you want to test with automated testing.
• All type casting for input remains in the main method. Your methods should operate on the correct data types, not take Strings as input and then try to parse those. Leave the parsing (and error-handling for the parsing) in the main method.

Answer 2

1. Displose of all static methods.
2. In your main create instance of Calculator and run calculate method.
3. Now you can test Calcultor calculate method with JUnit

Restricting scope to package will enable you to test this class, if test class will be in same package (but in test source)

public class Calculator {

public static void main(String[] args) {
    String s1 = getInput("Enter a numeric value: ");
    String s2 = getInput("Enter a numeric value: ");
    String op = getInput("Enter 1=ADD, 2=Subtract, 3=Multiply, 4=Divide ");

new Calculator().calculate(s1, s2, op);
}

public void calculate(String s1, String s2, String op)
    int opInt = Integer.parseInt(op);
    double result = 0;

    switch (opInt) {
    case 1:
        result = addValues(s1, s2);
        break;
    case 2:
        result = subtractValues(s1, s2);
        break;
    case 3:
        result = multiplyValues(s1, s2);
        break;
    case 4:
        result = divideValues(s1, s2);
        break;

    default:
        System.out.println("You entered an incorrect value");
        return;
    }

    System.out.println("The answer is " + result);

}

 double divideValues(String s1, String s2) {
    double d1 = Double.parseDouble(s1);
    double d2 = Double.parseDouble(s2);
    double result = d1 / d2;
    return result;
}

 double multiplyValues(String s1, String s2) {
    double d1 = Double.parseDouble(s1);
    double d2 = Double.parseDouble(s2);
    double result = d1 * d2;
    return result;
}

 double subtractValues(String s1, String s2) {
    double d1 = Double.parseDouble(s1);
    double d2 = Double.parseDouble(s2);
    double result = d1 - d2;
    return result;
}

 double addValues(String s1, String s2) {
    double d1 = Double.parseDouble(s1);
    double d2 = Double.parseDouble(s2);
    double result = d1 + d2;
    return result;
}

 String getInput(String prompt) {
    BufferedReader stdin = new BufferedReader(
            new InputStreamReader(System.in));

    System.out.print(prompt);
    System.out.flush();

    try {
        return stdin.readLine();
    } catch (Exception e) {
        return "error: " + e.getMessage();
    }
}

Answer 3

In JUnit testing you can include classes in your test file. There is no need to copy and paste code from a class and put it in the test file. It would look more like:

Calculator c = new Calculator();

c.myFunction();

You can add assert statements into your test function as well to confirm that you are getting the correct results from the function call.

I have only done JUnit tests using Eclipse, but essentially you create a new JUnit file (just like you would a Class), and that automatically sets up the basic structure of the file. Then from there you can add in however many tests you want. You may import whatever classes you need as well.