Fix Contacts tests

[vne]

Correctly define sendSignedTransaction in web3.eth mock to fix the contracts tests that throw web3 error

Related Issue

Presumably, #139 is related. Please, note that this PR addresses only Contracts tests issues, so after merging Travis will still fail because of failing Kafka tests (see PR https://github.com/DAVFoundation/dav-js/pull/140).

Motivation and Context

Contracts tests were failing.

How Has This Been Tested?

npm run jest

$ node -v v10.15.3 $ npm -v 6.4.1

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Enhancement that improves upon existing functionality

Checklist:

• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [x] I have read the CONTRIBUTING document.
• [x] I have added tests to cover my changes.
• [ ] All new and existing tests passed.

[mariolo1985]

hey @vne thanks for fixing issues related to #139 and the failing jest tests 👍