tests fail when yaml files used by in spring-boot 1.2 application

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What steps will reproduce the problem?
1. create a minimal spring-boot 1.2 project (spring-boot-starter and 
spring-boot-starter-test), class App with @SpringBootApplication annotation
2. add empty file application.yaml in main/resources
3. create a new empty test and add @SpringApplicationConfiguration annotation 
and extend AbstractTestNGSpringContextTests

@SpringApplicationConfiguration (classes = App.class)
public class AppTest extends AbstractTestNGSpringContextTests {
  @Test
  public void f() {       
  }
}
4. run the test
What is the expected output? What do you see instead?
Fails with an error:
FAILED CONFIGURATION: @BeforeClass springTestContextPrepareTestInstance
java.lang.NoSuchMethodError: 
org.yaml.snakeyaml.Yaml.<init>(Lorg/yaml/snakeyaml/constructor/BaseConstructor;L
org/yaml/snakeyaml/representer/Representer;Lorg/yaml/snakeyaml/DumperOptions;Lor
g/yaml/snakeyaml/resolver/Resolver;)V

What version of the product are you using? On what operating system?
testng 6.8.21, Windows 7, Eclipse (Kepler)

Please provide any additional information below.
Workarounds:
1) use application.properties instead [and no other yaml property files]
2) downgrade to spring.boot 1.1, say 1.1.11

Original issue reported on code.google.com by nkalnber...@gmail.com on 3 Mar 2015 at 11:46