### Question:
ReflectionHelper { static Source<Object> getSourceOrFail(String name) { Source<Object> src = FluidRegistry.source(Objects.requireNonNull(name)); if (src == null) { throw new IllegalArgumentException("Unable to find the source " + name); } return src; } private  ReflectionHelper(); static void set(Object mediator, Field field, Object source); static void invokeFunction(Object mediator, Method method); static void invokeTransformationMethod(Object mediator, Method method); static Object getSourceToInject(Class<?> clazz, Type type, Source<Object> source); static void inject(Object mediator);  }### Answer:
@Test public void testGettingAMissingSource() { FluidRegistry.register("my-source", Source.empty()); Source<Object> source = ReflectionHelper.getSourceOrFail("my-source"); assertThat(source).isNotNull(); try { ReflectionHelper.getSourceOrFail("missing"); fail("The source should be missing"); } catch (IllegalArgumentException e) { } }