How do you handle InvalidUseOfMatchersException in Mockito

Understanding the Exception

The `InvalidUseOfMatchersException` is thrown when Mockito detects that you are using a combination of raw values and argument matchers in a method call. For example, if a method takes two parameters and you use a raw value for one parameter and an argument matcher (like `any()`, `eq()`, etc.) for the other, Mockito will throw this exception.

Example of Incorrect Usage

java
// Incorrect usage: Mixing raw value with matcher
doNothing().when(cmd).dnsCheck(HOST, any(InetAddressFactory.class));

In this example, `HOST` is a raw value, and `any(InetAddressFactory.class)` is an argument matcher. This combination is not allowed.

Correcting the Exception

To fix the `InvalidUseOfMatchersException`, you must ensure that either all parameters are raw values or all parameters are argument matchers. Here are the correct ways to handle it:

Using All Argument Matchers

If you want to use argument matchers, you should use them for all parameters:

java
// Correct usage: Using all matchers
doNothing().when(cmd).dnsCheck(anyString(), any(InetAddressFactory.class));

In this corrected version, both parameters are specified using argument matchers (`anyString()` and `any(InetAddressFactory.class)`).

Using All Raw Values

Alternatively, you can use raw values for all parameters:

java
// Correct usage: Using all raw values
doNothing().when(cmd).dnsCheck(HOST, new InetAddressFactory());

Here, both parameters are raw values (`HOST` and a new instance of `InetAddressFactory`).

Additional Tips

- Avoid Mixing Matchers and Raw Values: Always ensure that you are consistent in using either all matchers or all raw values in a method call.
- Use `eq()` for Specific Values: If you need to match a specific value, use `eq()` to wrap it as a matcher. For example, `eq(HOST)` instead of just `HOST`.
- Check Mockito Version: Ensure you are using a compatible version of Mockito. Some features or behaviors might change between versions.

By following these guidelines, you can effectively handle and resolve the `InvalidUseOfMatchersException` in your Mockito tests.