When we develop a test case, we have one expected output and one actual output. **Assertion** helps us compare these outputs and evaluate whether a given test case is pass or fail. 

We can use assertion in JUnit after we import it into the file:

```JAVA
import static org.junit.Assert.*;
```

> All assertion methods are available in JUnit `assert` class.

#    
## Assert Methods

The JUnit provides all assert methods by default.

Let's take a look at few assert methods:

- **assertEquals**: Evaluates whether the expected and actual outputs of the test case are equal.
- **assertArrayEquals**: Evaluates whether the expected and actual arrays are equal.
- **assertNull**: Evaluates if the object is Null.
- **asserNottNull**: Evaluates if object is not Null.
- **assertSame**: Evaluates if two objects are pointing to the same object. 
- **assertNotSame**: Evaluates if two objects are not pointing to the same object. 
- **assertTrue**: Evaluates if the condition is true.
- **assertFalse**: Evaluates if the condition is false. 

## Code
Let's take a look at a few assertion examples.





import static org.junit.Assert.*;  
import org.junit.*;                

public class assertTest { 

  //assertEqual compares two strings 
    @Test
    public void assertEquslTest() {
        String stractual = "This is the testcase1";
        assertEquals("This is the testcase1", stractual);
    }
    
    //assertArrayEqualsTest compares two array
    @Test
    public void assertArrayEqualsTest() {
        int expected[] = {1,2,3,4,5};
        int actual[]   = {1,2,3,4,5};
        assertArrayEquals(expected, actual);
    }
    
    //assertFalse checks value is false
    @Test
	public void assertFalseTest() {
		boolean value = false;
		assertFalse(value);
	}

    //assertTrue checks value is true
    @Test
	public void assertTrueTest() {
		boolean value = true;
		assertTrue(value);
	}
}

import React from 'react';
import { shallow, configure } from 'enzyme';
import Adapter from 'enzyme-adapter-react-16';

configure({ adapter: new Adapter() });

import HelloWorld from './app';

var TestResult = function() {
    this.succeeded = false;
    this.reason = "";
    this.input = "";
    this.expected_output = "";
    this.actual_output = "";
}

export const executeTests = function() {

  var results = [];

  result = new TestResult();
  result.input = 'HelloWorld Component';
  result.expected_output = "span containing text 'Hello World'"

  let wrapper = shallow(<HelloWorld />);

  // Call your Challenge function here.

  let type = wrapper.type();
  let testSuccessful = true;
  let failureReason;

  if (type !== 'span') {
    testSuccessful = false;
    failureReason = "You need to render exactly one span HTML element";
  } else if (wrapper.props().children != "Hello World") {
     testSuccessful = false;
     failureReason = "You have rendered wrong message in your span element";
  }

  result.actual_output = wrapper.html();

  if (testSuccessful) {
    result.succeeded = true;
    result.reason = "Succeeded"
  } else {
    result.succeeded = false;
    result.reason = failureReason;
  }

  results.push(result);

  return results;
}


assert

React

Dart

GoJS React

Typescript React

Vue.js

`OK (4 tests)` shows that all 4 test cases are passing.

If one of these test cases fails, the output will be `Tests run: 4,  Failures: 1`.

junit.tar.gz

What are the assertions in JUnit?

Assertions in JUnit compare expected and actual outputs using methods like assertEquals, assertArrayEquals, assertNull, assertNotNull, assertSame, assertNotSame, assertTrue, and assertFalse.