Improve tests

[kyarik]

• Improve formatting of queries in tests.
• Improve test descriptions.
• Compare uninitialized variables against undefined. Comparing against null will pass whether the variables were assigned the request/response object or left undefined. However, the intention of the expectation is to check that uninitialized variables were assigned a value (i.e., not undefined).
• Remove duplicated test it('will send request and response when using thunk'). There is already another test which tests that the options function is passed the request and response: it('provides an options function with arguments').