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Java Unit Testing in Java How to Test Using Before to not repeat yourself

Posted by Bala Selvam
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Bala Selvam
Python Development Techdegree Student 30,590 Points

Use the @Before method to instantiate a new Calculator and use that instance in each method.

I have no Idea what I am doing wrong here

com/example/CalculatorTest.java 
package com.example;

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

import static org.junit.Assert.*;

public class CalculatorTest {

    @Before
    public void setUp() throws Exception {
      calculator = new Calculator

    }

    @Test
    public void addingMultipleNumbersProducesResult() throws Exception {
        Calculator calculator = new Calculator();

        int answer = calculator.addNumbers(1 ,2, 3);

        assertEquals(6, answer);
    }

    @Test
    public void addingSingleNumberTotalsAppropriately() throws Exception {
        Calculator calculator = new Calculator();

        int answer = calculator.addNumbers(1);

        assertEquals(1, answer);
    }
}
com/example/Calculator.java 
package com.example;

public class Calculator {

    public int addNumbers(int... numbers) {
        int total = 0;
        for (int number : numbers) {
            total += number;
        }
        return total;
    }
}

1 Answer

calp
calp
10,317 Points
calp
calp
10,317 Points

You need to remove the lines in the two test methods that also create a calculator and only create the calculator once in the setup method.

To do this you will need to create an instance variable (so that all of the methods inside of the class can access it) and then initialize that variable in the setUp method. Here is the code.

package com.example;

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

import static org.junit.Assert.*;

public class CalculatorTest {
    private Calculator c;

    @Before
    public void setUp() throws Exception {
        c = new Calculator();
    }

    @Test
    public void addingMultipleNumbersProducesResult() throws Exception {
        int answer = c.addNumbers(1 ,2, 3);

        assertEquals(6, answer);
    }

    @Test
    public void addingSingleNumberTotalsAppropriately() throws Exception {
        int answer = c.addNumbers(1);

        assertEquals(1, answer);
    }
}

I have created the instance variable and called it c. I have then initialized that variable in the setUp method, removed the old Calculator variables from the two test methods and made them use the c variable.