Junit Testing Tips - Constructor Is Called Earlier Executing Exam Methods

Even though nigh all Java programmers either utilisation JUnit or TestNG for in that place unit of measurement testing withdraw along amongst approximately mock object generation libraries e.g. Mockito, but non everyone spends fourth dimension together with seek to acquire subtle details of these testing libraries, at to the lowest degree non inwards proportion of whatsoever pop framework like vending motorcar implementation every bit a coding exercise. If you lot aspect at closely, I bring initialized vending motorcar inwards the degree body, which is executed every bit role of the constructor.

I was assuming i instance of the vending motorcar is shared betwixt all examine methods, every bit I was non using @Before together with @After, JUnit four annotation for setup() together with tearDown().

In the kickoff test, i item from Inventory is consumed together with inwards minute examine approximately other item, but when you lot assert count of items based upon the previous test, it volition fail, because you lot are testing a dissimilar vending motorcar instance, which has dissimilar inventory.

So always, recall that JUnit calls the constructor of examine degree earlier executing the examine method. You tin verify it past times putting a System.out.println message inwards the constructor itself. Btw, if you lot are simply starting amongst JUnit or bring used it quite a long ago, together with then I propose you lot to kickoff refresh your concepts past times going through JUnit together with Mockito Crash Course. 

JUnit has already come upwards a long means amongst enhancements inwards JUnit 4.0 together with JUnit 5.0, the latest unloosen of JUnit.

Code Written inwards Constructor is Executed earlier each Test Method

a constructor.

In the output section, you lot tin encounter that message from constructor has appeared ii times, i for each examine case. This proves that the constructor of JUnit examine class is executed earlier each examine method.

import java.util.List;

import org.junit.Test;

import static org.junit.Assert.;

/**

  *

  * @author Javin

  */

public class VendingMachineTest {

    private VendingMachine motorcar = new VendingMachine();

  

    public VendingMachineTest(){

        System.out.println("JUnit Framework calls Constructor of examine degree earlier executing examine methods");

    }

    @Test

    public void buyDrinkWithExactAmount(){

        int toll = machine.choose(Item.COKE);

        assertEquals(70, price);

        assertEquals(Item.COKE, machine.currentItem);

      

        machine.insert(Coin.QUARTER);

        machine.insert(Coin.QUARTER);

        machine.insert(Coin.DIME);

        machine.insert(Coin.DIME);

        assertEquals(70, machine.balance);

        assertEquals(7, (int) machine.coinInvertory.getCount(Coin.DIME));

        assertEquals(7, (int) machine.coinInvertory.getCount(Coin.QUARTER));

      

        Item i = machine.dispense();

        assertEquals(Item.COKE, i);

        assertEquals(4, (int) machine.itemInvertory.getCount(i));

      

        List alter = machine.getChange();

        assertTrue(change.isEmpty());

      

      

    }

  

    @Test

    public void buyDrinkWithMoreAmount(){

        int toll = machine.choose(Item.SPRITE);

        assertEquals(90, price);

        assertEquals(Item.SPRITE, machine.currentItem);

      

        machine.insert(Coin.QUARTER);

        machine.insert(Coin.QUARTER);

        machine.insert(Coin.QUARTER);

        machine.insert(Coin.QUARTER);

      

        assertEquals(100, machine.balance);

        assertEquals(9, (int) machine.coinInvertory.getCount(Coin.QUARTER));

      

        Item i = machine.dispense();

        assertEquals(Item.SPRITE, i);

        assertEquals(4, machine.itemInvertory.getCount(i));

        //this was failing, because past times default VM initialize inventory amongst v items

        assertEquals(4, machine.itemInvertory.getCount(Item.COKE));

      

        List alter = machine.getChange();

        assertEquals(1, change.size());

        assertEquals(Coin.DIME, change.get(0));

        assertEquals(4, machine.coinInvertory.getCount(Coin.DIME));

             

    }

Output:

Testsuite: test.VendingMachineTest

JUnit Framework calls Constructor of examine class before executing examine methods

JUnit Framework calls Constructor of examine class before executing examine methods

Tests run: 2, Failures: 1, Errors: 0, Time elapsed: 1.421 sec

Result

------------- ---------------- ---------------

Testcase: buyDrinkWithMoreAmount(test.VendingMachineTest):      FAILED

expected:<4> but was:<5>

junit.framework.AssertionFailedError: expected:<4> but was:<5>

        at test.VendingMachineTest.buyDrinkWithMoreAmount(VendingMachineTest.java:63)

That's all guys. I experience this is a worth knowing special if you lot are using JUnit for writing unit of measurement examine inwards your Java project. Sometimes, nosotros bring a põrnikas inwards unit of measurement examine itself, but nosotros suspect our code. So it must for all Java developers to know the nitty-gritty of JUnit testing framework every bit well.

Further Learning
Unit Testing In Java With JUnit
JUnit together with Mockito Crash Course
Learn Unit Testing amongst JUnit & Mockito inwards thirty Steps

Thanks for reading this article therefore far. If you lot similar this JUnit tips together with then delight portion amongst your friends together with colleagues. If you lot bring whatsoever questions or feedback together with then delight driblet a note.

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