util.concurrent, like nearly all our packages, has two .gwt.xml files: one
    for prod and one for tests. However, unlike our other packages, as of this
    writing it has test supersource but no prod supersource.

    GWT happens to use the prod .gwt.xml, so it looks for no supersource for
    tests, either. This causes it to fail to find AtomicLongMapTest.

### Build Commands

```bash
mvn compile                              # Compile
mvn test                                 # Run all tests
mvn test -Dtest=SuggesterTest           # Run specific test
mvn package                              # Package JAR
mvn formatter:format license:format     # Format code and apply licenses
mvn clean jacoco:prepare-agent test jacoco:report  # Generate coverage report
```

### Adding New Features

import org.junit.Ignore;

/**
 * A generic JUnit test which tests operations on a NavigableMap. Can't be invoked directly; please
 * see {@code NavigableMapTestSuiteBuilder}.
 *
 * @author Jesse Wilson
 * @author Louis Wasserman
 */
@GwtIncompatible
@Ignore("test runners must not instantiate and run this directly, only via suites we build")
// @Ignore affects the Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.

import org.junit.Ignore;

/**
 * A generic JUnit test which tests operations on a NavigableMap. Can't be invoked directly; please
 * see {@code NavigableMapTestSuiteBuilder}.
 *
 * @author Jesse Wilson
 * @author Louis Wasserman
 */
@GwtIncompatible
@Ignore("test runners must not instantiate and run this directly, only via suites we build")
// @Ignore affects the Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.

		}
		return
	}
}

// DetectTestLeak -  snapshots the currently running goroutines and returns a
// function to be run at the end of tests to see whether any
// goroutines leaked.
// Usage: `defer DetectTestLeak(t)()` in beginning line of benchmarks or unit tests.
func DetectTestLeak(t TestErrHandler) func() {
	initialStackSnapShot := NewLeakDetect()
	return func() {
		initialStackSnapShot.DetectLeak(t)
	}
}

It also includes what has changed, how validations are now more correct and strict, possible caveats, etc.

You can read it to understand better what has changed.

## Tests { #tests }

Make sure you have [tests](../tutorial/testing.md) for your app and you run them on continuous integration (CI).

This way, you can do the upgrade and make sure everything is still working as expected.

    }

    @Nested
    @DisplayName("Interface Method Contract Tests")
    class InterfaceMethodTests {

        @Test
        @DisplayName("Should fixup host with FQDN")
        void testFixupHost() {
            String fqdn = "server.example.com";

            // Test with mock
            doNothing().when(mockReferralData).fixupHost(fqdn);
            mockReferralData.fixupHost(fqdn);

import org.junit.Ignore;

/**
 * Base class for multiset collection tests.
 *
 * @author Jared Levy
 */
@GwtCompatible
@Ignore("test runners must not instantiate and run this directly, only via suites we build")
// @Ignore affects the Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.
@SuppressWarnings("JUnit4ClassUsedInJUnit3")

            } else {
                task.jvmArgs("-XX:+UseG1GC");
            }
        });

        // TODO: fix usages of IT tests depending on Tests methods so this extension is not necessary
        GradleUtils.extendSourceSet(project, SourceSet.TEST_SOURCE_SET_NAME, SOURCE_SET_NAME);

        // add alias task that is easier to type

import java.util.Collection;
import org.junit.Ignore;

/**
 * Tests {@link java.util.Set#hashCode}.
 *
 * @author George van den Driessche
 */
@GwtCompatible
@Ignore("test runners must not instantiate and run this directly, only via suites we build")
// @Ignore affects the Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.
@SuppressWarnings("JUnit4ClassUsedInJUnit3")