Currently, if a container is not on the classpath when the test suite is executed, Arquillian fails with a NullPointerException:

java.lang.NullPointerException
at org.jboss.arquillian.impl.DeployableTestBuilder.build(DeployableTestBuilder.java:88)
at org.jboss.arquillian.impl.DeployableTestBuilder.build(DeployableTestBuilder.java:77)
at org.jboss.arquillian.junit.Arquillian.<init>(Arquillian.java:93)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at org.junit.internal.builders.AnnotatedBuilder.buildRunner(AnnotatedBuilder.java:31)
at org.junit.internal.builders.AnnotatedBuilder.runnerForClass(AnnotatedBuilder.java:24)
at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:57)
at org.junit.internal.builders.AllDefaultPossibilitiesBuilder.runnerForClass(AllDefaultPossibilitiesBuilder.java:29)

Arquillian should instead fail the test, reporting that no container implementation is present on the classpath.