1.  ***test test***
2.  ___test test___
3.  *test **test***
4.  **test *test***
5.  ***test* test**
6.  ***test** test*
7.  ***test* test**
8.  **test *test***
9.  *test **test***
10. _test __test___
11. __test _test___
12. ___test_ test__
13. ___test__ test_
14. ___test_ test__
15. __test _test___
16. _test __test___

Incorrect nesting:

1. *test **test* test**
2. _test __test_ test__
3. **test *test** test*
4. __test _test__ test_
5. *test  *test* test*
6. _test  _test_ test_
7. **test **test** test**
8. __test __test__ test__

No emphasis:

1. test* test *test
2. test** test **test
3. test_ test _test
4. test__ test __test

Middle-word emphasis (asterisks):

1.  *a*b
2.   a*b*
3.   a*b*c
4. **a**b
5.   a**b**
6.   a**b**c

Middle-word emphasis (underscore):

1.  _a_b
2.   a_b_
3.   a_b_c
4. __a__b
5.   a__b__
6.   a__b__c
7.   my_precious_file.txt

Tricky Cases:

1.  E**. **Test** TestTestTest
2.  E**. **Test** Test Test Test

Overlong emphasis:

Name: ____________  
Organization: ____  
Region/Country: __

_____Cut here_____

____Cut here____