Texas Whistleblower Protects State, Local Government Employees
Texas has a limited whistleblower protection. Texas Government Code Sec. 554 protects public employees who report violations of law to the appropriate law enforcement agency. See statute. The Texas Whistleblower Act provides for a 90 days deadline in which to file suit. It also requires an employee to first file a grievance if the state or local agency provides for a grievance procedure. If the employee files a grievance, then the duration of the grievance will toll the statute of limitations (ie, toll the deadline).
The good faith report of the violation of law would need to be made to the appropriate law enforcement agency. The report would need to be related to the reporting employee's official duties.
There is no equivalent statute for private employees. But, as I wrote earlier, a private employee would be protected if they were required to violate a criminal statute.
So, if you are a private employer, report your employer for violating some criminal law and get fired, then you have no protection. If you are a state or local government employee and are fired because you reported your employer for violating some law, then you can file suit.