@Test
  public void testQualifierFilterNoCase() throws IOException {
    String filterString = "QualifierFilter(=, 'regexstringnocase:pre*')";
    QualifierFilter qualifierFilter = doTestFilter(filterString, QualifierFilter.class);
    assertEquals(CompareOperator.EQUAL, qualifierFilter.getCompareOperator());
    assertTrue(qualifierFilter.getComparator() instanceof RegexStringComparator);
    RegexStringComparator regexStringComparator =
      (RegexStringComparator) qualifierFilter.getComparator();
    assertEquals("pre*", new String(regexStringComparator.getValue(), StandardCharsets.UTF_8));
    int regexComparatorFlags = regexStringComparator.getEngine().getFlags();
    assertEquals(Pattern.CASE_INSENSITIVE | Pattern.DOTALL, regexComparatorFlags);
  }
This class tests ParseFilter.java It tests the entire work flow from when a string is given by
the user and how it is parsed to construct the corresponding Filter object
hbase-server/src/test/java/org/apache/hadoop/hbase/filter/TestParseFilter.java