Unit test added for Variable node

[UgurAldanmaz]

This unit test is testing the thrown exception is
NLogConfigurationException or not when variable node is written to wrong
place.

For #1128

Configuration validation will be done at #1174

[codecov-io]

Current coverage is 73.54%

Merging #1173 into master will decrease coverage by -0.08% as of 7c4cea4

@@            master   #1173   diff @@
======================================
  Files          265     265       
  Stmts        15057   15057       
  Branches      1651    1652     +1
  Methods          0       0       
======================================
- Hit          11086   11073    -13
- Partial        417     420     +3
- Missed        3554    3564    +10

Review entire Coverage Diff as of 7c4cea4

---

Uncovered Suggestions

1. +0.08% via ...nternal/AspHelper.cs#206...218
2. +0.08% via ...nternal/AspHelper.cs#188...200
3. +0.08% via ...nternal/AspHelper.cs#170...182
4. See 7 more...

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[304NotModified]

Thanks! Can you also make a variant where the <variable> is after the <target>?

[s-sreenath]

Thanks! Can you also make a variant where the is after the ?

+1

[UgurAldanmaz]

Sure. I made it using InlineData and Theory :)

[UgurAldanmaz]

There are problems with Mono reference and Theory attribute (for Silverlight).

I am going to remove Theory attribute but I am not sure about Mono error. It is not related to this commit.

[s-sreenath]

@UgurAldanmaz may be you just need to surround with conditional statements.

[304NotModified]

Fixes #1128

[304NotModified]

Thanks! It had been merged!

[UgurAldanmaz]

Thanks! I am closing related issue.