SampleCode for OTP validation

// Using notification Pane

initiateDriver(extentReport); //To open the test App
try {
    Thread.sleep(10000);
} catch (InterruptedException e) {
    e.printStackTrace();
}

driver.openNotifications();//Open notification Panel
//To Fetch the Messaging/OTP related notification
System.out.println(driver.findElementByXPath("//*[@resource-id='android:id/big_text'  and contains(@text,'Your one time password')]").getText());
driver.navigate().back();// Close navigation pannel




// Using Messaging app

//Initialize the driver
initiateDriver(extentReport);//To Launch the Original App needs to be tested
try {
    Thread.sleep(10000);
} catch (InterruptedException e) {
    e.printStackTrace();
}
//Opening Messaging App
driver.startActivity("com.google.android.apps.messaging",".ui.ConversationListActivity");
driver.findElement(By.xpath("(//*[@resource-id='com.google.android.apps.messaging:id/conversation_snippet' " +
        "and" +
        " contains(@text,'Dear Subscriber ENG vs NZ')])[1]")).click();

try {
    Thread.sleep(3000);
} catch (InterruptedException e) {
    e.printStackTrace();
}
int msgSize= driver.findElements(By.xpath("//*[@resource-id='com.google.android.apps" +
        ".messaging:id/message_text']")).size();

System.out.println(driver.findElement(By.xpath("(//*[@resource-id='com.google.android.apps" +
        ".messaging:id/message_text'])["+msgSize+"]")).getText());  //Fetching the message with a particular type of Text

driver.startActivity("com.android.dialer","com.motorola.dialer.app.ExtendedDialtactsActivity"); // Switching back to Test ap