Added tests to medhistory model

[coveralls]

Pull Request Test Coverage Report for Build 819

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.005%) to 82.4%

---

Totals
Change from base Build 817:	0.005%
Covered Lines:	2973
Relevant Lines:	3608

---

💛 - Coveralls

[xShaivan]

Doing documentation as well in this merge commit.