Fixed broken unit tests: test_mssqlcliclient.py and test_completion_refresher.py

[geleems]

Fixed broken unit tests (test_mssqlcliclient.py and test_completion_refresher.py)

Failed unit tests in test_mssqlcliclient.py

• test_schema_table_views_and_columns_query
  • Cause: client.get_views() failed to retrieve list of views since it uses query with where clause WHERE table_type = 'View' that returns nothing on case-sensitive database
  • Fix: Remove the where clause and look up INFORMATION_SCHEMA.VIEWS instead of INFORMATION_SCHEMA.TABLES

Failed unit tests in test_completion_refresher.py

• test_ctor

  • Causes:
    • refresher.refreshers.keys() returns only 5 refresher names defined in completion_refresher.py
    • set comparison should have been used instead of list comparison to verify if all elements of A are in B and all elements of B are in A
  • Fix
    • Update the expected_handlers with appropriate refreshers
    • Use set comparison instead of list

• test_refresh_with_callbacks

  • Cause: it used wrong mock object for mssqlcliclient which blows up when mssqlcliclient.connect_to_database() is called.
  • Fix: Create and use mock object for mssqlcliclient with connect_to_database() implementation.

Changed use unit test framework unittest since class type unit test that extends unittest.TestCase (such as test_mssqlcliclient.py) are a lot more convenient to run and manage.

[pensivebrian]

Can you also add a little more to the description? What the issue was, and how the PR fixes the issue?

[pensivebrian]

Please update the main description about the issue and how this PR fixes the issues.