26 test0(S s,  U val, S expected)  in test0()  function
38     test0(S(""), 'a', S(""));  in test()
40     test0(S("a"), 'a', S(""));  in test()
41     test0(S("a"), 'b', S("a"));  in test()
43     test0(S("ab"), 'a', S("b"));  in test()
44     test0(S("ab"), 'b', S("a"));  in test()
45     test0(S("ab"), 'c', S("ab"));  in test()
46     test0(S("aa"), 'a', S(""));  in test()
47     test0(S("aa"), 'c', S("aa"));  in test()
49     test0(S("abc"), 'a', S("bc"));  in test()
50     test0(S("abc"), 'b', S("ac"));  in test()
51     test0(S("abc"), 'c', S("ab"));  in test()
52     test0(S("abc"), 'd', S("abc"));  in test()
54     test0(S("aab"), 'a', S("b"));  in test()
55     test0(S("aab"), 'b', S("aa"));  in test()
56     test0(S("aab"), 'c', S("aab"));  in test()
57     test0(S("abb"), 'a', S("bb"));  in test()
58     test0(S("abb"), 'b', S("a"));  in test()
59     test0(S("abb"), 'c', S("abb"));  in test()
60     test0(S("aaa"), 'a', S(""));  in test()
61     test0(S("aaa"), 'b', S("aaa"));  in test()
65     test0(S("aba"), opt(),    S("aba"));  in test()
66     test0(S("aba"), opt('a'), S("b"));  in test()
67     test0(S("aba"), opt('b'), S("aa"));  in test()
68     test0(S("aba"), opt('c'), S("aba"));  in test()