Dependency 'junit:junit:4.13' not found

This error message means that the JUnit dependency with version 4.13 cannot be found in your project. To resolve this issue, you can follow these steps:

1. Check your project's build configuration or dependency management file (such as `pom.xml` for Maven or `build.gradle` for Gradle) to make sure that the JUnit dependency is correctly specified. For example, in Maven, you should have the following dependency entry:

   <dependency>
       <groupId>junit</groupId>
       <artifactId>junit</artifactId>
       <version>4.13</version>
       <scope>test</scope>
   </dependency>

2. Verify your internet connectivity to ensure that your build tool can download the required dependency from the repository.

3. If you are using an IDE, try refreshing the project or restarting the IDE to reload the dependencies.

4. If the issue persists, you can try deleting the local repository cache for JUnit and then let your build tool resolve and download the dependency again.

If you have further questions or need more assistance, please let me know!