Several tests of the DOM normalize() function.
test1 (two non-empty text nodes): PASSED
test2 (three non-empty text nodes): PASSED
test3 (non-empty text nodes mixed with elements): PASSED
test4 (single empty text node): PASSED
test5 (empty text node between elements): PASSED
test6 (empty text nodes before non-empty node): PASSED
test7 (empty text nodes after non-empty node): PASSED
test8 (empty text nodes between non-empty nodes): PASSED
test9 (empty and non-empty text nodes mixed with elements): PASSED
test10 (mixed cases including deeper nested text nodes): PASSED