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

Posted by Varun Manoj
Varun Manoj
1,541 Points

Hi there, I get a null result for the tests that I run. Why does this happen?

I was wondering whether this is because the calculator object has no constructor?

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

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

import static org.junit.Assert.*;

public class CalculatorTest {

  Calculator calculator;

    @Before
    public void setUp() throws Exception {

       Calculator calculator = new Calculator();
    }

    @Test
    public void addingMultipleNumbersProducesResult() throws Exception {


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

        assertEquals(6, answer);
    }

    @Test
    public void addingSingleNumberTotalsAppropriately() throws Exception {


        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

Geovanie Alvarez
Geovanie Alvarez
21,500 Points
Geovanie Alvarez
Geovanie Alvarez
21,500 Points

You are duplicating the same variable

Calculator calculator;  // <-------- here

    @Before
    public void setUp() throws Exception {

       Calculator calculator = new Calculator();  // <-------- and here
    }

change to this instead

Calculator calculator; // <-------- here

    @Before
    public void setUp() throws Exception {
      calculator = new Calculator();  // <-------- and here
    }