I think the method was added for easier migration to JUnit 4 tooling, and occasionally this exception pops up on older code bases that use JUnit 3.8. The Eclipse JUnit 4 test runner would appear to switch back to calling the junit.framework.* code when running JUnit 3.8 tests.
If you do not see it in your project dependencies then one of the libraries might be using 3.8. If you cannot remove the library from there then try using the @RunWith(JUnit4.class) annotation.
SO I'm guessing you still have JUnit 3.8.1 lurking about on your classpath, and it's clashing with the Eclipse test runner. Either get rid of that JAR, or "upgrade" it to 3.8.2.
The getExpected() method on junit.framework.ComparisonFailure was only added in JUnit 3.8.2 (remember, junit.framework package is from JUnit 3.8, whereas JUnit 4 uses org.junit). The method wasn't there in 3.8.1, which is the most common version of 3.x still out there.