Java get test resource file

How to read a text-file resource into java unit test?

When writing Java unit tests, it is often necessary to read resources, such as text files, as part of the test setup. However, accessing these resources can be challenging, especially when the resources are packaged within the Java application or library. In this scenario, the resources cannot be accessed directly as the file system path may not be known, and the resources are stored within the classpath, which is not directly accessible at runtime. The following methods provide ways to read a text-file resource into a Java unit test:

Method 1: Using ClassLoader

To read a text-file resource into Java unit test using ClassLoader, follow these steps:

1. Get the ClassLoader object from the current thread’s contextClassLoader.
2. Use the getResourceAsStream() method of the ClassLoader object to get an InputStream object for the text file.
3. Use the BufferedReader class to read the text file line by line.

import java.io.BufferedReader; import java.io.InputStream; import java.io.InputStreamReader; public class TextFileReader  public static String readTextFile(String filename)  StringBuilder result = new StringBuilder(); try (InputStream inputStream = TextFileReader.class.getClassLoader().getResourceAsStream(filename); BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream)))  String line; while ((line = reader.readLine()) != null)  result.append(line).append("\n"); > > catch (Exception e)  e.printStackTrace(); > return result.toString(); > >

In this example, we have a static method readTextFile() that takes the filename of the text file as an argument and returns its contents as a string. The method uses the ClassLoader object of the TextFileReader class to get an InputStream object for the file. It then uses a BufferedReader object to read the file line by line and append each line to a StringBuilder object. Finally, it returns the contents of the StringBuilder object as a string.

To use this method in a unit test, you can call it like this:

import org.junit.Test; import static org.junit.Assert.assertEquals; public class TextFileReaderTest  @Test public void testReadTextFile()  String expected = "Hello, world!\n"; String actual = TextFileReader.readTextFile("test.txt"); assertEquals(expected, actual); > >

In this example, we have a unit test that calls the readTextFile() method with the filename «test.txt». It then compares the expected result («Hello, world!\n») with the actual result returned by the method. If they are equal, the test passes.

Method 2: Using ClassPathResource

To read a text-file resource into a Java unit test using ClassPathResource , you can follow these steps:

1. Add the necessary dependencies to your project. For example, if you’re using Maven, add the following to your pom.xml file:

dependency> groupId>org.springframeworkgroupId> artifactId>spring-coreartifactId> version>5.3.8version> dependency>

1. Create a ClassPathResource object, passing the path of the resource file as a parameter. For example, if your resource file is located in the src/test/resources directory and is named test.txt , you can create a ClassPathResource object like this:

ClassPathResource resource = new ClassPathResource("test.txt");

1. Use the getInputStream() method of the ClassPathResource object to get an InputStream object for the resource file. You can then read the contents of the file from the InputStream . For example:

try (InputStream inputStream = resource.getInputStream())  // read the contents of the file from the input stream // . > catch (IOException e)  // handle the exception >

Here’s the complete code example:

import org.springframework.core.io.ClassPathResource; import java.io.IOException; import java.io.InputStream; public class Test  public static void main(String[] args)  ClassPathResource resource = new ClassPathResource("test.txt"); try (InputStream inputStream = resource.getInputStream())  // read the contents of the file from the input stream // . > catch (IOException e)  // handle the exception > > >

Note that the ClassPathResource class is part of the Spring Framework, so you need to add the Spring dependencies to your project in order to use it.

Method 3: Using InputStream

To read a text-file resource into a Java unit test using InputStream, follow these steps:

1. Get the InputStream object of the text-file resource using the getResourceAsStream() method of the ClassLoader class.

InputStream inputStream = getClass().getClassLoader().getResourceAsStream("filename.txt");

BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));

String line; while ((line = reader.readLine()) != null) < // process the line >

Here’s an example code snippet that demonstrates how to read a text-file resource into a Java unit test using InputStream:

import java.io.BufferedReader; import java.io.InputStream; import java.io.InputStreamReader; public class TextFileReader  public static void main(String[] args) throws Exception  InputStream inputStream = TextFileReader.class.getClassLoader().getResourceAsStream("filename.txt"); BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream)); String line; while ((line = reader.readLine()) != null)  System.out.println(line); > reader.close(); > >

In this example, replace «filename.txt» with the name of your text-file resource. The text from the file will be printed to the console.

Method 4: Using FileSystemResource

To read a text-file resource into Java unit test using FileSystemResource, you can follow these steps:

import org.springframework.core.io.FileSystemResource; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader;

FileSystemResource resource = new FileSystemResource("src/test/resources/testFile.txt");

InputStream inputStream = resource.getInputStream();

BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));

String line; while ((line = reader.readLine()) != null)  // Do something with the text >

Here’s the complete code example:

import org.springframework.core.io.FileSystemResource; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; public class TestClass  public void testMethod() throws IOException  FileSystemResource resource = new FileSystemResource("src/test/resources/testFile.txt"); InputStream inputStream = resource.getInputStream(); BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream)); String line; while ((line = reader.readLine()) != null)  // Do something with the text > > >

In this example, we first import the required classes, then create a FileSystemResource object with the file path. We then get the InputStream from the resource object, create a BufferedReader object to read the text from the InputStream, and finally read the text from the BufferedReader object.

Note that you may need to handle exceptions when using these classes and methods.

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Read File and Resource in JUnit Test

This quick tutorial is going to cover how to read file and resource in JUnit test where may need to access files or resources under the src/test/resources folder.

1. Sample Project Directory Layout

Let’s take a look at a sample project directory layout of a project called junit5-tutorial which contains some JUnit 5 examples.

Sample Project Directory Layout

• src/main/java contains all application/library sources
• src/main/resources contains application/library resources
• src/test/java contain test sources
• src/test/resources test resources

In this article, we mainly focus on the test sources and resources. There are several cases that we may want to read file and resource in JUnit tests such as:

• File or resource contains the test data
• Tests are related to file operations
• Configuration files

To illustrate for how to read file and resource in JUnit test, in the above example, let’s assume that the FileUtilsTest test class in the test sources (src/test/java) will need to read a file called lorem_ipsum.txt in the test resources (src/test/resources).

2. Read File and Resource in JUnit Test Examples

2.1. Using ClassLoader’s Resource

Let’s see an example as the following:

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Получите путь к каталогу /src/test/resources в JUnit

Иногда во время модульного тестирования нам может потребоваться прочитать какой-либо файл из пути к классам или передать файл тестируемому объекту. Или у нас может быть файл в src/test/resources с данными для заглушек, которые могут использоваться такими библиотеками, как WireMock .

В этом руководстве мы покажем, как прочитать путь к каталогу / src/test/resources .

2. Зависимости Maven​

Во-первых, нам нужно добавить JUnit 5 к нашим зависимостям Maven:

 dependency>   groupId>org.junit.jupitergroupId>   artifactId>junit-jupiter-engineartifactId>   version>5.8.1version>   dependency> 

Мы можем найти последнюю версию JUnit 5 на Maven Central .

2. Использование java.io.File ​

Самый простой подход использует экземпляр класса java.io.File для чтения каталога /src/test/resources путем вызова метода getAbsolutePath() :

 String path = "src/test/resources";    File file = new File(path);   String absolutePath = file.getAbsolutePath();    System.out.println(absolutePath);    assertTrue(absolutePath.endsWith("src/test/resources")); 

Обратите внимание, что этот путь относится к текущему рабочему каталогу , то есть к каталогу проекта.

Давайте посмотрим на пример вывода при запуске теста на macOS:

 /Users/user.name/my_projects/tutorials/testing-modules/junit-5-configuration/src/test/resources 

3. Использование пути ​

Далее мы можем использовать класс Path , представленный в Java 7 .

Во-первых, нам нужно вызвать статический фабричный метод — Paths.get(). Затем мы преобразуем Path в File. В конце нам просто нужно вызвать getAbsolutePath() , как в предыдущем примере:

 Path resourceDirectory = Paths.get("src","test","resources");   String absolutePath = resourceDirectory.toFile().getAbsolutePath();    System.out.println(absolutePath);    Assert.assertTrue(absolutePath.endsWith("src/test/resources")); 

И мы получим тот же вывод, что и в предыдущем примере:

 /Users/user.name/my_projects/tutorials/testing-modules/junit-5-configuration/src/test/resources 

4. Использование ClassLoader ​

Наконец, мы также можем использовать ClassLoader :

 String resourceName = "example_resource.txt";    ClassLoader classLoader = getClass().getClassLoader();   File file = new File(classLoader.getResource(resourceName).getFile());   String absolutePath = file.getAbsolutePath();    System.out.println(absolutePath);    assertTrue(absolutePath.endsWith("/example_resource.txt")); 

И давайте посмотрим на вывод:

 /Users/user.name/my_projects/tutorials/testing-modules/junit-5-configuration/target/test-classes/example_resource.txt 

Обратите внимание, что на этот раз у нас есть файл /junit-5-configuration/target/test-classes/example-resource.txt . Он отличается, когда мы сравниваем результат с предыдущими методами.

Это связано с тем, что ClassLoader ищет ресурсы в пути к классам . В Maven скомпилированные классы и ресурсы помещаются в каталог /target/ . Вот почему на этот раз у нас есть путь к ресурсу пути к классам.

5. Вывод​

Подводя итог, в этом кратком руководстве мы обсудили, как читать каталог /src/test/resources в JUnit 5.

В зависимости от наших потребностей мы можем достичь нашей цели несколькими способами: используя классы File , Paths или ClassLoader .

Как всегда, вы можете найти все наши примеры на нашем проекте GitHub !

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