SpringTestContextBeforeTestMethod failed in Maven spring-test

I try to setup a project with spring-test using TestNg in Maven. The code is like:

@ContextConfiguration(locations={"test-context.xml"})
public class AppTest extends AbstractTestNGSpringContextTests {

    @Test
    public void testApp() {
        assert true;
    }
}

A test-context.xml simply defined a bean:

<bean id="app" class="org.sonatype.mavenbook.simple.App"/>

I got error for Failed to load ApplicationContext when running mvn test from command line, seems it cannot find the test-context.xml file; however, I can get it run correctly inside Eclipse (with TestNg plugin).

So, test-context.xml is under src/test/resources/, how do I indicate this in the pom.xml so that 'mvn test' command will work?
Thanks,

UPDATE:

Thanks for the reply. Cannot load context file error was caused by I moved the file arround in different location since I though the classpath was the problem. Now I found the context file seems loaded from the Maven output, but the test is failed:

Running TestSuite
May 25, 2010 9:55:13 AM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
INFO: Loading XML bean definitions from class path resource [test-context.xml]
May 25, 2010 9:55:13 AM org.springframework.context.support.AbstractApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.support.GenericApplicationContext@171bbc9: display name [org.springframework.context.support.GenericApplicationContext@171bbc9]; startup date [Tue May 25 09:55:13 PDT 2010]; root of context hierarchy
May 25, 2010 9:55:13 AM org.springframework.context.support.AbstractApplicationContext obtainFreshBeanFactory
INFO: Bean factory for application context [org.springframework.context.support.GenericApplicationContext@171bbc9]: org.springframework.beans.factory.support.DefaultListableBeanFactory@1df8b99
May 25, 2010 9:55:13 AM org.springframework.beans.factory.support.DefaultListableBeanFactory preInstantiateSingletons
INFO: Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@1df8b99: defining beans [app,org.springframework.context.annotation.internalCommonAnnotationProcessor,org.springframework.context.annotation.internalAutowiredAnnotationProcessor,org.springframework.context.annotation.internalRequiredAnnotationProcessor]; root of factory hierarchy
Tests run: 3, Failures: 2, Errors: 0, Skipped: 1, Time elapsed: 0.63 sec <<< FAILURE!

Results :

Failed tests: 
  springTestContextBeforeTestMethod(org.sonatype.mavenbook.simple.AppTest)
  springTestContextAfterTestMethod(org.sonatype.mavenbook.simple.AppTest)

Tests run: 3, Failures: 2, Errors: 0, Skipped: 1

If I use spring-test version 3.0.2.RELEASE, the error becomes:

org.springframework.test.context.testng.AbstractTestNGSpringContextTests.springTestContextPrepareTestInstance() is depending on nonexistent method null

Here is the structure of the project:

simple
|-- pom.xml
`-- src
    |-- main
    |   `-- java
    `-- test
        |-- java
        `-- resources
            |-- test-context.xml
            `-- testng.xml

testng.xml:

<suite name="Suite" parallel="false">
  <test name="Test">
    <classes>
      <class name="org.sonatype.mavenbook.simple.AppTest"/>
    </classes>
  </test>
</suite>

test-context.xml:

 <beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans 
         http://www.springframework.org/schema/beans/spring-beans-2.0.xsd"
    default-lazy-init="true">
    <bean id="app" class="org.sonatype.mavenbook.simple.App"/>
 </beans>

In the pom.xml, I add testng, spring, and spring-test artifacts, and plugin:

<dependency>
  <groupId>org.testng</groupId>
  <artifactId>testng</artifactId>
  <version>5.1</version>
  <classifier>jdk15</classifier>
  <scope>test</scope>
</dependency>
<dependency>
  <groupId>org.springframework</groupId>
  <artifactId>spring</artifactId>
  <version>2.5.6</version>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-test</artifactId> 
    <version>2.5.6</version> 
    <scope>test</scope> 
</dependency>

<build>
<finalName>simple</finalName>
<plugins>
  <plugin>
    <artifactId>maven-compiler-plugin</artifactId>
    <configuration>
      <source>1.6</source>
      <target>1.6</target>
    </configuration>
  </plugin>
  <plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-surefire-plugin</artifactId>
    <configuration>   
      <suiteXmlFiles>
        <suiteXmlFile>src/test/resources/testng.xml</suiteXmlFile>
      </suiteXmlFiles>
    </configuration>
  </plugin>
</plugins>

Basically, I replaced 'A Simple Maven Project' Junit with TestNg, hope it works.

UPDATE:

I think I got the problem (still don't know why) –
Whenever I extends AbstractTestNGSpringContextTests or AbstractTransactionalTestNGSpringContextTests, the test will failed with this error:

Failed tests:
  springTestContextBeforeTestMethod(org.sonatype.mavenbook.simple.AppTest)
  springTestContextAfterTestMethod(org.sonatype.mavenbook.simple.AppTest)

So, eventually the error went away when I override the two methods.
I don't think this is the right way, didn't find much info from spring-test doc.
If you know spring test framework, please shred some light on this.