gistfile1.java

    private final Set<AssertionError> assertionErrors = Sets.newHashSet();

    @BeforeTest
    public void assertErrorTrap() {
        assertionErrors.clear();
        Thread.setDefaultUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() {
            @Override
            public void uncaughtException(Thread t, Throwable e) {
                if (e instanceof AssertionError) {
                    assertionErrors.add((AssertionError) e);
                }
            }
        });
    }

    @AfterTest
    public void checkThreadAssertions() {
        assertEquals(assertionErrors.size(), 0, "Background threads should not fail assertions");
    }