@Test
public void testLongestSubstringLength() {

    Assert.assertEquals(0, ForeignKeys.longestSubstringLength("", "abc"));
    Assert.assertEquals(0, ForeignKeys.longestSubstringLength("abc", ""));
    Assert.assertEquals(3, ForeignKeys.longestSubstringLength("abc", "abcd"));
    Assert.assertEquals(3, ForeignKeys.longestSubstringLength("abcd", "abc"));
    Assert.assertEquals(6, ForeignKeys.longestSubstringLength("abababbad", "ababba"));
    Assert.assertEquals(5, ForeignKeys.longestSubstringLength("cababababac", "dababad"));
}