问多浏览器上的TestNG并行执行总是只考虑单个浏览器

EN

<?xml version="1.0" encoding="UTF-8"?>
<suite name="Parallel Tests" verbose="1" thread-count="10" parallel="tests">
    <tests> 
        <test name="Test1">
            <parameters>
                <parameter name="platform" value="Windows" />
                <parameter name="browser" value="chrome" />
                <parameter name="version" value="8" />
            </parameters>
            <classes>
                <class name="com.tribune.uiautomation.testscripts.TestEngine"/>
            </classes>
        </test> <!-- Test -->

        <test name="Test2">
            <parameters>
                <parameter name="platform" value="Windows" />
                <parameter name="browser" value="firefox" />
                <parameter name="version" value="8" />
            </parameters>
            <classes>
                <class name="com.tribune.uiautomation.testscripts.TestEngine"/>
            </classes>
        </test> <!-- Test -->

    </tests>    
</suite> <!-- Suite -->

@BeforeTest
    @Parameters("browser")
    public void beforeTest(String browser){
        try{    
            Property.BrowserName = browser;
            System.out.println("BrowserName got from XML is "+Property.BrowserName);
}

@test
public void Execute test() {

//code for launching browser & performing tests...
}

log4j:WARN [] should be System.out or System.err.
log4j:WARN Using previously set target, System.out by default.
[TestNG] Running:
  D:\Selenium_Projects\WorkSpace_Personal\TribuneWebScriptLess\TestNG.xml

BrowserName got from XML is chrome
BrowserName got from XML is firefox

//from here onwards it is considering only firefox browser only (i.e. both the tests mentioned in TestNG.xml are running in firefox only)