preserve-order controls the method execution order

1. Preserve-order is set to true, methods are executed in order f3, f1, f2

	<test name="TestSuite" preserve-order="true">
		<classes>
			<class name="com.testng.annotations.test.ClassName">
				<methods>
					<include name="f3"></include>
					<include name="f1"></include>
					<include name="f2"></include>
				</methods>
			</class>
		</classes>
	</test>

2. Preserve-order is set to false, methods are executed in order f1, f2, f3

	
<test name="TestSuite" preserve-order="false">
<classes>
<class name="com.testng.annotations.test.ClassName">
<methods>
<include name="f3"></include>
<include name="f1"></include>
<include name="f2"></include>
</methods>
</class>
</classes>
</test>

3. The default is false, that is, the methods are executed in the order f1, f2, f3