unit testing.

## Adding Guava Testlib to your build

Guava testlib's Maven group ID is `com.google.guava` and its artifact ID is `guava-testlib`.

To add a dependency on Guava testlib using Maven, use the following:

```xml
<dependency>
  <groupId>com.google.guava</groupId>
  <artifactId>guava-testlib</artifactId>
  <version>33.3.1-jre</version>
  <scope>test</scope>
</dependency>
```

<?xml version="1.0" encoding="UTF-8"?>
<metadata>
  <groupId>org.apache.maven.its</groupId>
  <artifactId>a</artifactId>
  <version>0.1</version>
  <versioning>
    <versions>
      <version>0.1</version>
    </versions>
    <lastUpdated>20091023222756</lastUpdated>
  </versioning>

<project>
  <modelVersion>4.0.0</modelVersion>
  <groupId>maven-test</groupId>
  <artifactId>t06-d</artifactId>
  <packaging>jar</packaging>
  <version>1.0</version>

<project>
  <modelVersion>4.0.0</modelVersion>
  <groupId>maven-test</groupId>
  <artifactId>t06-d</artifactId>
  <packaging>jar</packaging>
  <version>1.1</version>

<project>
  <modelVersion>4.0.0</modelVersion>
  <groupId>maven-test</groupId>
  <artifactId>t07-d</artifactId>
  <packaging>jar</packaging>
  <version>1.1</version>

<project>
  <modelVersion>4.0.0</modelVersion>
  <groupId>maven-test</groupId>
  <artifactId>t10-b</artifactId>
  <packaging>jar</packaging>
  <version>1.0</version>

<project>
  <parent>
    <artifactId>p0</artifactId>
    <groupId>maven</groupId>
    <version>1.0</version>
    <relativePath>../../pom.xml</relativePath>
  </parent>
  <modelVersion>4.0.0</modelVersion>
  <artifactId>p1</artifactId>

                // Compute goal coordinates
                String groupId, artifactId, version, goal;
                String[] p = mojo.getGoal().trim().split(":");
                if (p.length == 3) {
                    // <groupId>:<artifactId>:<goal>
                    groupId = p[0];
                    artifactId = p[1];
                    version = null;
                    goal = p[2];

    }

    @Test
    void testMissingGroupId() throws Exception {
        SimpleProblemCollector result = validate("missing-groupId-pom.xml");

        assertViolations(result, 0, 1, 0);

        assertEquals("'groupId' is missing.", result.getErrors().get(0));
    }

    @Test
    void testInvalidCoordinateIds() throws Exception {

            + "  <groupId>thegroup</groupId>\n"
            + "  <artifactId>base1</artifactId>\n"
            + "  <version>1</version>\n"
            + "  <packaging>pom</packaging>\n"
            + "  <dependencyManagement>\n"
            + "    <dependencies>\n"
            + "      <dependency>\n"
            + "        <groupId>thegroup</groupId>\n"
            + "        <artifactId>base2</artifactId>\n"