How should a developer write unit tests for a private method in an Apex class?

[Reference:Testing Apex Code, , , Below is the formatted response for the provided question, adhering to the specified format and requirements. The question falls under the Salesforce Platform and Declarative Features topic, as it involves securing SOQL queries against injection vulnerabilities in the context of Visualforce, which is a key concept in the Salesforce Platform Developer I certification. The answer is based on official Salesforce Platform Developer I documentation, with a comprehensive explanation and references to relevant Salesforce documentation. Since the question asks for two correct answers, the response will identify both and explain why they are safe, as well as why the others are not., , ]