To run unit test via Maven, issue this command : 
mvn test
This will run the entire unit tests in your project.

Case Study

Create two unit tests and run it via Maven. See a simple Java class for testing :
package com.mkyong.core;

public class App {
 public static void main(String[] args) {

  System.out.println(getHelloWorld());

 }

 public static String getHelloWorld() {

  return "Hello World";

 }

 public static String getHelloWorld2() {

  return "Hello World 2";

 }
}

Unit Test 1

Unit test for getHelloWorld() method.
package com.mkyong.core;

import junit.framework.Assert;
import org.junit.Test;

public class TestApp1 {

 @Test
 public void testPrintHelloWorld() {

  Assert.assertEquals(App.getHelloWorld(), "Hello World");

 }

}

Unit Test 2

Unit test for getHelloWorld2() method.
package com.mkyong.core;

import junit.framework.Assert;
import org.junit.Test;

public class TestApp2 {

 @Test
 public void testPrintHelloWorld2() {

  Assert.assertEquals(App.getHelloWorld2(), "Hello World 2");

 }

}

Run Unit Test

See below examples to run unit test with Maven.
Example 1
To run the entire unit test (TestApp1 and TestApp2), issue this command :
mvn test
Example 2
To run single test (TestApp1), issue this command :
mvn -Dtest=TestApp1 test
Example 3
To run single test (TestApp2), issue this command :
mvn -Dtest=TestApp2 test
Note
For more “mvn test” examples, refer to this maven-test plugin documentation.