Add tests for parallel execution

[mahendrakariya]

We can check for the following points in this test.

• Is execution passing?
• Are the reports getting aggregated?

For asserting that the reports are getting aggregated, a very simple check could be to parse result array in reports (xml or json) and see if the length of that array is equal to total specs in the project.

[sriv]

Closing, there are tests for parallel execution now.