What is <scope> under <dependency> in pom.xml for?

Looking at documentation http://maven.apache.org/surefire/maven-surefire-plugin/examples/testng.html, we can see <scope> tag under <dependency>

What is that and how can we use it for running test?

The <scope> element can take 6 values: compile, provided, runtime, test, system and import.

This scope is used to limit the transitivity of a dependency, and also to affect the classpath used for various build tasks.

> compile > This is the default scope, used if none is specified. Compile dependencies are available in all classpaths of a project. Furthermore, those dependencies are propagated to dependent projects.

> provided

> This is much like compile, but indicates you expect the JDK or a container to provide the dependency at runtime. For example, when building a web application for the Java Enterprise Edition, you would set the dependency on the Servlet API and related Java EE APIs to scope provided because the web container provides those classes. This scope is only available on the compilation and test classpath, and is not transitive.

>runtime

>This scope indicates that the dependency is not required for compilation, but is for execution. It is in the runtime and test classpaths, but not the compile classpath.

>test

>This scope indicates that the dependency is not required for normal use of the application, and is only available for the test compilation and execution phases.

>system

>This scope is similar to provided except that you have to provide the JAR which contains it explicitly. The artifact is always available and is not looked up in a repository.

>import (only available in Maven 2.0.9 or later)

>This scope is only used on a dependency of type pom in the section. It indicates that the specified POM should be replaced with the dependencies in that POM's section. Since they are replaced, dependencies with a scope of import do not actually participate in limiting the transitivity of a dependency.

To answer the second part of your question: > How can we use it for running test?

Note that the test scope allows to use dependencies only for the test phase.

Read the documentation for full details.

added good images with explain scopes

Six Dependency scopes:

• compile: default scope, classpath is available for both src/main and src/test
• test: classpath is available for src/test
• provided: like complie but provided by JDK or a container at runtime
• runtime: not required for compilation only require at runtime
• system: provided locally provide classpath
• import: can only import other POMs into the <dependencyManagement/>, only available in Maven 2.0.9 or later. It is not always practical to change parent, many projects already specify a parent project to manage their organization standards. dependencyManagement allows us to add parent project without making parent, it's like multiple inheritance.

Scope tag is always use to limit the transitive dependencies and availability of the jar at class path level.If we don't provide any scope then the default scope will work i.e. Compile .

.pom dependency scope can contain:

• compile - available at Compile-time and Run-time
• provided - available at Compile-time. (this dependency should be provided by outer container like OS...)
• runtime - available at Run-time
• test - test compilation and run time
• system - is similar to provided but exposes <systemPath>path/some.jar</systemPath> to point on .jar
• import - is available from Maven v2.0.9 for <type>pom</type> and it should be replaced by effective dependency from this file <dependencyManagement/>

If we don't provide any scope then the default scope is compile, If you want to confirm, simply go to Effective pom tab in eclipse editor, it will show you as compile.