Get the Path of the /src/test/resources Directory in JUnit

JUnit is a popular testing framework that helps in writing unit tests for Java applications. Sometimes, we have configuration files or test data stored in the /src/test/resources directory. In this article, we will learn how to retrieve the path of files or the directory itself from the /src/test/resources folder in JUnit tests using different approaches.

Setting Up the Maven Project

To begin, let's set up a simple Maven project. Use the following command to create a Maven project, and cd into the project directory:

mvn archetype:generate -DgroupId=com.mycompany.app -DartifactId=my-app -DarchetypeArtifactId=maven-archetype-quickstart -DarchetypeVersion=1.5 -DinteractiveMode=false
cd my-app

Create a JSON File under the /src/test/resources Directory

We will create a sample test-data.json file inside the /src/test/resources directory so we can access the file path in one of our tests later.

Filename: src/test/resources/test-data.json

{
  "test": {
    "key": "value"
  }
}

Accessing the Path Using Different Approaches

1. Using the ClassLoader Method

JUnit provides a ClassLoader with helper methods to access files from the classpath. We will update the AppTest.java file to access the file path of test-data.json using ClassLoader.

Filename: src/test/java/com/mycompany/app/AppTest.java

package com.mycompany.app;

import org.junit.jupiter.api.Test;
import java.io.File;
import java.net.URL;

public class AppTest {

    @Test
    public void testGetResourcePath() {
        // Get the resource using the ClassLoader
        URL resourceUrl = getClass().getClassLoader().getResource("test-data.json");

        // Convert URL to File to get the absolute path
        File resourceFile = new File(resourceUrl.getPath());
        System.out.println("Path to test-data.json: " + resourceFile.getAbsolutePath());
    }
}

Run the test:

Run the test using the below command:

mvn test

Output:

This approach uses the classpath to access the resource file and prints its absolute path.

2. Using java.io.File

You can directly access the file using the File class from the java.io package. In this case, we will specify the relative path and then convert it to an absolute path.

Filename: src/test/java/com/mycompany/app/AppTest.java

package com.mycompany.app;

import org.junit.jupiter.api.Test;
import java.io.File;

import static org.junit.jupiter.api.Assertions.assertTrue;

public class AppTest {

    @Test
    void testGetResourcePath() {
        // Use File class to get the file path
        File file = new File("src/test/resources/test-data.json");

        // Verify if the file exists and print its absolute path
        assertTrue(file.exists(), "File should exist in the given path");
        System.out.println("File path: " + file.getAbsolutePath());
    }
}

Output:

This method checks if the file exists at the given relative path and prints its absolute path.

3. Using Path from java.nio.file.Paths

Another way to handle file paths more efficiently is to use the Path class from the java.nio.file package. This approach makes the code more readable by using a comma-separated list of path elements.

Filename: src/test/java/com/mycompany/app/AppTest.java

package com.mycompany.app;

import org.junit.jupiter.api.Test;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

import static org.junit.jupiter.api.Assertions.assertTrue;

public class AppTest {

    @Test
    void testGetResourcePath() {
        // Use Path class to access the file path
        Path path = Paths.get("src", "test", "resources", "test-data.json");

        // Verify if the file exists using the Path and print its absolute path
        assertTrue(Files.exists(path), "File should exist using Path");
        System.out.println("Path: " + path.toAbsolutePath());
    }
}

Output:

This approach uses java.nio.file.Paths to access and print the absolute path.

Getting the Path of the /src/test/resources Directory

If you want to retrieve the path of the /src/test/resources directory itself rather than a specific file, you can use the File class to get the directory's absolute path.

@Test
void testGetResourcesDirectoryPath() {
    String resourcesPath = new File("src/test/resources").getAbsolutePath();
    System.out.println("Path to /src/test/resources: " + resourcesPath);
    assertTrue(new File(resourcesPath).exists(), "Resources directory should exist");
}

This prints the absolute path to the /src/test/resources directory.

Conclusion

In this article, we explored three different methods to get the path of files in the /src/test/resources directory in a JUnit test that are, using ClassLoader, java.io.File, and java.nio.file.Paths. Additionally, we demonstrated how to retrieve the path of the directory itself. These approaches are essential when working with test resources in JUnit.