How to set environment variables in JUnit 5 for test case?

From this other SO answer https://stackoverflow.com/a/59635733/2185719:

There is JUnit Pioneer, a "JUnit 5 extension pack".

jUnit Pioneer offers an annotation that sets environment variables for a test. For example:

@Test @SetEnvironmentVariable(key = "PATH", value = "") void testPath_isEmpty() { assertThat(System.getenv("PATH")).isEmpty(); } 

You can't within the actual java process because these environmental values using getenv are immutable.

One way would be to start another vm or another process where you could introduce your new environment value.

Another way would be to switch to System.getProperty, but be sure you understand the differences.

https://www.baeldung.com/java-system-get-property-vs-system-getenv

Here is a little testcode:

public class EnvironmentVarsTest { private static int counter = 0; @BeforeEach public void setUp() { counter = counter + 1; System.setProperty("simple_test_env_property", String.valueOf(counter)); } @Test public void testFirst() { printOutValues(); } @Test public void testSecond() { printOutValues(); } private void printOutValues() { System.out.println("--------------------"); System.out.println("val=" + counter); System.out.println("envval=" + System.getProperty("simple_test_env_property")); } } 

Simple solution if you use Gradle, you can add following to your build.gradle

test { environment "ENV_VAR_NAME", "ENV_VAR_VALUE" } 

Link to Gradle doc: https://docs.gradle.org/current/dsl/org.gradle.api.tasks.testing.Test.html#org.gradle.api.tasks.testing.Test:environment

This can be achieved with https://github.com/webcompere/system-stubs/tree/master/system-stubs-jupiter

 @ExtendWith(SystemStubsExtension.class) class TestClass { @SystemStub private EnvironmentVariables environmentVariables = new EnvironmentVariables("demoVar", "val"); @Test void test() { // can use the environment assertThat(System.getenv("demoVar")).isEqualTo("val"); // can also change the environment environmentVariables.set("foo", "bar"); // environment variables restored to previous state when // test ends } } 

Here is a solution using Kotlin DSL (build.gradle.kts):

tasks.withType<Test> { environment["myFirst"] = "bunny" // OR environment( "mySecond" to "7249", "myThird" to "curtain" ) } 

The environment variables will be available both in the tests and in the main code:

val name = System.getenv().get("myFirst") 

Sidenote: You can also disable/enable your tests based on environment variables:

@Test @EnabledIfEnvironmentVariable(named = "myFirst", matches = "bunny", disabledReason = "Oh no") public void myTest() { // ... } 

The common practice is to use System properties instead of environment variables. In this case you will run your java/maven/gradle command or whatever you use to run your tests with option -D demoVar="{your_value}". for maven goal:

 maven clean install -DdemoVar="test" 

for java jar:

 java -jar xxx.jar -DdemoVar="test" 

You will be able to get it from code with System.getProperty("demoVar").

If you really need to use environment variable, use OS functionality. For linux:

demoVar="test" mvn clean install 

For windows PowerShell:

$env:demoVar = 'test'; mvn clean install