Existing test file without test class obstruct generation #160

Description

If a test file with some name has already been created, but there is no test class in it, generating tests in this file will not be finished successfully.

To Reproduce

• Create class A
• Create file ATest without class ATest in similar package in test root
• Generate tests for A

Expected behavior

Tests are generated successfully. The content of ATest file is overwritten with generated test code.

Actual behavior

Test generation fails with error popup: "Failed to Create Class"