@Test
    public void testHead() {
        assertMetrics("head:0","a","a");
        assertMetrics("head:0","y","a");
        assertMetrics("head:1","a","x a");
        assertMetrics("head:2","a b c","x x a b c");
        assertMetrics("head:2","a b c","x x c x x a b");
        assertMetrics("head:2", "a b c", "x x c x x x x x x x x x x x x x x x a b");
    }
Tests of calculation of all the string match metrics.
Add true as the fourth parameter to assertMetrics to see a trace of what the test is doing.

@author bratseth
searchlib/src/test/java/com/yahoo/searchlib/ranking/features/fieldmatch/test/FieldMatchMetricsTestCase.java