Update test asserts on stubs to use sinon asserts

[moniika]

The basics

• I branched from develop
• My pull request is against develop
• My code follows the style guide

The details

Resolves

n/a

Proposed Changes

Updates test asserts on stubs to use sinon asserts

Reason for Changes

• Better assert messages
• In some cases, clearer intention

Test Coverage

Ran mocha tests

Tested on:

• Desktop Chrome

Additional Information

Used the following regex to perform cleanup:

Search	Replace
chai\.assert\((.+)\.called(Once|Twice|Thrice)\);	sinon\.assert\.called$2\($1\);
chai\.assert\.isTrue\((.+)\.called(Once|Twice|Thrice)\);	sinon\.assert\.called$2\($1\);
chai\.assert\((.+)\.notCalled\);	sinon\.assert\.notCalled\($1\);
chai\.assert\.isTrue\((.+)\.notCalled\);	sinon\.assert\.notCalled\($1\); [no occurrences]
chai\.assert\.isFalse\((.+)\.notCalled\);	sinon\.assert\.isCalled\($1\); [no occurrences]
chai\.assert\.isFalse\((.+)\.calledOnce\);	sinon\.assert\.notCalled\($1\); [separately checked to confirm intention]