If you believe that you have been terminated for some other reason that your employer does not want to tell you, you should see an employment lawyer.
Otherwise, file for unemployment. Although your employer may lawfully terminate you even though it is mistaken about failing the test, you may still show you did not do so and receive unemployment.
Depending on whether you are an "at-will" employee, you may have a case for wrongful termination. The real question may be, "What is the true reason they are terminating you?" If it is based upon an illegal reason (retaliation, discrimination, or public policy), you may have a separate cause of action. You should contact a lawyer concerning this matter.