Getting Error in XML testng file while running the test case in a suite

Question

I am trying to run a testng xml file in a suite.But when i run file
as run as testng suite i am getting below error in console

org.testng.TestNGException: org.xml.sax.SAXParseException; lineNumber: 37; columnNumber: 9; The content of element type "suite" must match "(groups?,(listeners|packages|test|parameter|method-selectors|suite-files)*)".
at org.testng.TestNG.parseSuite(TestNG.java:327)
at org.testng.TestNG.initializeSuitesAndJarFile(TestNG.java:348)
at org.testng.TestNG.initializeEverything(TestNG.java:995)
at org.testng.remote.support.RemoteTestNG6_12.initialize(RemoteTestNG6_12.java:22)
at org.testng.remote.AbstractRemoteTestNG.run(AbstractRemoteTestNG.java:97)
at org.testng.remote.RemoteTestNG.initAndRun(RemoteTestNG.java:251)
at org.testng.remote.RemoteTestNG.main(RemoteTestNG.java:77)

Caused by: org.xml.sax.SAXParseException; lineNumber: 37; columnNumber: 9; The content of element type "suite" must match "(groups?,(listeners|packages|test|parameter|method-selectors|suite-files)*)". at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.createSAXParseException(ErrorHandlerWrapper.java:203) at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.error(ErrorHandlerWrapper.java:134) at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:396) at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:327) at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:284) at com.sun.org.apache.xerces.internal.impl.dtd.XMLDTDValidator.handleEndElement(XMLDTDValidator.java:1994) at com.sun.org.apache.xerces.internal.impl.dtd.XMLDTDValidator.endElement(XMLDTDValidator.java:879) at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanEndElement(XMLDocumentFragmentScannerImpl.java:1783) at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:2970) at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:606) at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(XMLNSDocumentScannerImpl.java:118) at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:510) at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:848) at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:777) at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:141) at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1213) at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:643) at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl.parse(SAXParserImpl.java:327) at javax.xml.parsers.SAXParser.parse(SAXParser.java:195) at org.testng.xml.XMLParser.parse(XMLParser.java:38) at org.testng.xml.SuiteXmlParser.parse(SuiteXmlParser.java:16) at org.testng.xml.SuiteXmlParser.parse(SuiteXmlParser.java:9) at org.testng.xml.Parser.parse(Parser.java:152) at org.testng.xml.Parser.parse(Parser.java:233) at org.testng.TestNG.parseSuite(TestNG.java:295) ... 6 more

Since i am new to automation testing i am not able to find out why is the issue arises.I checked with all syntax error and i feel that it
is correct.But i am not able to solve this issue.This is my xml file which i am trying to run but getting error

    <?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE suite SYSTEM "http://testng.org/testng-1.0.dtd" >
    <suite name="Merck Production Smoke Test Automation Test Suite">
    <parameter name="appURL" value="https://webqws.sial.com"/>
    <parameter name="browserType" value="chrome"/>   
    <listeners>
    <listener class-name="customListener.TestNGCustomReportListener"> 
    </listener>
    <listener class-name="customListener.Customreporter"/>
    </listeners>
    <!--  --> <test name="Merck Production Suite - Automation Scripts 
    Execution - US">
    <parameter name="countryName" value="United States"/>      
    <classes>
    <class name="testScript.Merck_Web_eCommerce_SmokeTest"/>   
    </classes>    
    </test> -->    
    <test name="Merck Production Suite - Automation Scripts Execution - UK">    
    <parameter name="countryName" value="United Kingdom"/>    
    <classes>    
    <class name="testScript.Merck_Web_eCommerce_SmokeTest"/>    
    </classes>     
    </test>    
    <!-- <test name="Merck Production Suite - Automation Scripts Execution - 
   INDIA">
   <parameter name="countryName" value="India"/>   
   <classes>
   <class name="testScript.Merck_Web_eCommerce_SmokeTest"/>
   </classes>   
   </test>  -->    
   </suite>

Answer 1

(most probable) Problem reasons:

1. Unmatched closing --> in your xml file.

   Solution: Delete it.

2. (After fixing 1., I still had:) "invalid DTD"(!), like here.

   Solution: Use https!;) (in <!DOCTYPE suite SYSTEM "https://testng.org/testng-1.0.dtd" >)