Client (server) tests

[mprudnik]

• [x] tests and linter show no problems (npm t)
• [x] tests are added/updated for bug fixes and new features
• [x] code is properly formatted (npm run fmt)
• [ ] description of changes is added in CHANGELOG.md
• [ ] update .d.ts typings

[tshemsedinov]

       connection.on('message', (data, isBinary) => {
-        if (isBinary) this.binary(client, data);
+        if (isBinary) this.binary(client, new Uint8Array(data));
         else this.message(client, data);
       });

[mprudnik]

@tshemsedinov Tests are passing now. Could you please review how the tests are written before landing this PR? The idea was to use only client code to test it separately, create mock server for each case and run a basic success case scenario.

[mprudnik]

@tshemsedinov Yes, ready

[tshemsedinov]

@mprudnik Landed, Thanks!