Added basic test for DatabaseHelper

Refs #7
Added test for DatabaseHelper_getSong()

Refs #7
Cleaned up the imports for the tests

Refs #7
Cleaned up the tests

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Added song for tests

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Added test for DatabeseHelper_addToDatabaseFromUrl()

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Added DatabaseHelper_getSongsMatching()

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Added another test for DatabaseHelper_addToDatabaseFromUrl()

Refs #7
Added tests for DatabaseHelper_deleteSong()

Refs #7
Added tests for DatabaseHelper_deleteAllSong()

Refs #7