maven - How to set env variable from within junit test case? -

i followed how set env variables maven run test correctly? , configured pom :

<plugin>    <groupid>org.apache.maven.plugins</groupid>    <artifactid>maven-surefire-plugin</artifactid>    <version>2.15</version>    <configuration>        <systempropertyvariables>            <sendgrid_username>username</sendgrid_username>            <sendgrid_password>password</sendgrid_password>        </systempropertyvariables>    </configuration> </plugin> 

when run mvn test command, giving following error,

error in custom provider, java.lang.illegalstateexception: sendgrid_password env variable must set. 

what doing wrong ?

when doing research find answer, found out following : processbuilder can used set env processes spawned it. dont know whether processbuilder helps in case not spawning processes. project maven project , run test mvn test command.

can body explains me how set env situations (i.e., maven + junit )

i able set properties problem how set environment variable program expecting env variable.

if read documentation correctly, configuration use is:

 <environmentvariables>        <sendgrid_username>username</sendgrid_username>        <sendgrid_password>password</sendgrid_password>  </environmentvariables> 

could issue?

source: http://maven.apache.org/surefire/maven-surefire-plugin/test-mojo.html#environmentvariables