Legal Question in Employment Law in California

The employer is entitled to set and change hours, duties, titles, compensation, benefits, leaves, vacations, holidays, etc. In general, unless an employee is civil service, in a union, or has a written employment contract, they are an 'at will' employee that can be disciplined or fired any time for any reason, with or without �cause� or explanation, other than for illegal discrimination, harassment or retaliation under the ADA [age], Civil Rights [race, sex, ethnic, religion, pregnancy, etc], Whistle-blower, or similar statutes. The employee's goal should be to keep the employer happy. That would include testing when asked.