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.

    Our workaround is to tell GWT that util.concurrent and all other packages
    have prod supersource, even if they have none. GWT is happy to ignore us

        // Verify stack trace is available
        StackTraceElement[] stackTrace = runtimeException.getStackTrace();
        assertNotNull(stackTrace);
        assertTrue(stackTrace.length > 0);

        // Verify the cause's stack trace is also available
        StackTraceElement[] causeStackTrace = runtimeException.getCause().getStackTrace();
        assertNotNull(causeStackTrace);
        assertTrue(causeStackTrace.length > 0);
    }

        // Verify stack trace exists
        StackTraceElement[] stackTrace = exception.getStackTrace();
        assertNotNull(stackTrace);
        assertTrue(stackTrace.length > 0);

        // Verify cause's stack trace is also available
        StackTraceElement[] causeStackTrace = exception.getCause().getStackTrace();
        assertNotNull(causeStackTrace);
        assertTrue(causeStackTrace.length > 0);
    }

    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.

    Our workaround is to tell GWT that util.concurrent and all other packages
    have prod supersource, even if they have none. GWT is happy to ignore us

    assertSame(EXCEPTION, record.getThrown());
  }

  public void testConcurrentModification() throws Exception {
    // Tests for the absence of a bug where logging while iterating over the
    // stored log records causes a ConcurrentModificationException
    assertTrue(handler.getStoredLogRecords().isEmpty());
    ExampleClassUnderTest.foo();
    ExampleClassUnderTest.foo();
    for (LogRecord unused : handler.getStoredLogRecords()) {

                    return (int) misses.incrementAndGet();
                  }
                });

    // To start, fill up the cache.
    // Each miss both increments the counter and causes the map to grow by one,
    // so until evictions begin, the size of the map is the greatest return
    // value seen so far
    while (cache.getUnchecked(nextRandomKey()) < maximumSize) {}

    requests.set(0);

    assertThat(getCausalChain(ex)).containsExactly(ex, re, iae, sue).inOrder();
    assertSame(sue, Iterables.getOnlyElement(getCausalChain(sue)));

    List<Throwable> causes = getCausalChain(ex);
    assertThrows(UnsupportedOperationException.class, () -> causes.add(new RuntimeException()));
  }

  public void testGetCasualChainNull() {
    assertThrows(NullPointerException.class, () -> getCausalChain(null));
  }

### Usage scanner

    checkFromStringCase("google.com:25\t", 1, null, 99, false);
    checkFromStringCase("google.com:0x25 ", 1, null, 99, false);
  }

  public void testFromStringUnparseableNonsense() {
    // Some nonsense that causes parse failures.
    checkFromStringCase("[goo.gl]", 1, null, 99, false);
    checkFromStringCase("[goo.gl]:80", 1, null, 99, false);
    checkFromStringCase("[", 1, null, 99, false);

    checkFromStringCase("google.com:25\t", 1, null, 99, false);
    checkFromStringCase("google.com:0x25 ", 1, null, 99, false);
  }

  public void testFromStringUnparseableNonsense() {
    // Some nonsense that causes parse failures.
    checkFromStringCase("[goo.gl]", 1, null, 99, false);
    checkFromStringCase("[goo.gl]:80", 1, null, 99, false);
    checkFromStringCase("[", 1, null, 99, false);