Feat/tanlang/add unit test to models layer

[LinZexiao]

关联的Issues (Related Issues)

close filecoin-project/venus#5235

改动 (Proposed Changes)

附注 (Additional Info)

自查清单 (Checklist)

在你认为本 PR 满足被审阅的标准之前，需要确保 / Before you mark the PR ready for review, please make sure that:

• 符合Venus项目管理规范中关于PR的相关标准 / The PR follows the PR standards set out in the Venus project management guidelines
• 具有清晰明确的commit message / All commits have a clear commit message.
• 包含相关的的测试用例或者不需要新增测试用例 / This PR has tests for new functionality or change in behaviour or not need to add new tests.
• 包含相关的的指南以及文档或者不需要新增文档 / This PR has updated usage guidelines and documentation or not need
• 通过必要的检查项 / All checks are green

[codecov-commenter]

Codecov Report

Merging #200 (ceb9a68) into master (77893b4) will increase coverage by 4.60%.
The diff coverage is 71.94%.

@@            Coverage Diff             @@
##           master     #200      +/-   ##
==========================================
+ Coverage   20.20%   24.80%   +4.60%     
==========================================
  Files         176      176              
  Lines       18541    18671     +130     
==========================================
+ Hits         3746     4632     +886     
+ Misses      14327    13476     -851     
- Partials      468      563      +95     

Flag	Coverage Δ
unittests	24.80% <71.94%> (+4.60%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
models/mysql/testing.go	72.72% <69.74%> (-27.28%)	⬇️
models/mysql/db.go	54.06% <82.35%> (+49.19%)	⬆️
models/mysql/cid_info.go	78.57% <100.00%> (+78.57%)	⬆️
paychmgr/simple.go	80.49% <0.00%> (+2.04%)	⬆️
models/badger/db.go	40.96% <0.00%> (+7.22%)	⬆️
models/badger/storage_ask.go	65.11% <0.00%> (+16.27%)	⬆️
models/badger/retrieval_ask.go	65.11% <0.00%> (+16.27%)	⬆️
models/badger/storage_deal.go	72.83% <0.00%> (+19.75%)	⬆️
models/badger/retrieval_deal.go	62.33% <0.00%> (+23.37%)	⬆️
... and 7 more

[hunjixin]

LGTM