Resolving the 'Cannot find symbol assertEquals' Error in JUnit Tests

Why does NetBeans report 'Cannot find symbol assertEquals' and '@Test' when writing unit tests?

package calculator;

import org.junit.Assert.*;
import org.junit.Test;

public class UnitTests{

    @Test
    public void checkAdd(){
        assertEquals(2, Calculator.rpnCalc(" 2 3 + "));  
    }
}

When writing unit tests in Java with JUnit, encountering the error 'Cannot find symbol assertEquals' usually indicates a problem with your import statements. This error can arise if the methods or annotations from JUnit are not correctly imported, or if the static imports are missing.

import static org.junit.Assert.assertEquals;
import org.junit.Test;

public class UnitTests{
    @Test
    public void checkAdd(){
        assertEquals(2, Calculator.rpnCalc(" 2 3 + "));  
    }
}

Causes

• Missing import for the static method assertEquals.
• Not importing the JUnit Test annotation.
• Using an incorrect version of JUnit that does not support these methods.

Solutions

• Add a static import for assertEquals by including 'import static org.junit.Assert.assertEquals;'.
• Ensure you are using the correct JUnit version (like JUnit 4 or higher).
• Import the Test annotation correctly with 'import org.junit.Test;'.
• Check your project setup to ensure JUnit library is included in your classpath.

Mistake: Not importing the static method assertEquals properly.

Solution: Use 'import static org.junit.Assert.assertEquals;' to import the assertEquals method.

Mistake: Not including the required JUnit imports.

Solution: Ensure to import both 'import org.junit.Test;' and 'import static org.junit.Assert.*;' correctly.