test: increasing unit tests coverage

[kosegor]

Description

closes: #484

---

Author Checklist

All items are required. Please add a note to the item if the item is not applicable and
please add links to any relevant follow up issues.

I have...

• included the correct type prefix in the PR title
• added ! to the type prefix if API or client breaking change
• added appropriate labels to the PR
• targeted the correct branch (see PR Targeting)
• provided a link to the relevant issue or specification
• added a changelog entry to CHANGELOG.md
• included comments for documenting Go code
• updated the relevant documentation or specification
• reviewed "Files changed" and left comments if necessary
• confirmed all CI checks have passed

Reviewers Checklist

All items are required. Please add a note if the item is not applicable and please add
your handle next to the items reviewed if you only reviewed selected items.

I have...

• confirmed the correct type prefix in the PR title
• confirmed all author checklist items have been addressed
• reviewed state machine logic
• reviewed API design and naming
• reviewed documentation is accurate
• reviewed tests and test coverage
• manually tested (if applicable)

[codecov]

Codecov Report

Merging #1962 (faebe07) into main (b0f1cfb) will increase coverage by 6.95%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1962      +/-   ##
==========================================
+ Coverage   68.43%   75.38%   +6.95%     
==========================================
  Files         100      100              
  Lines        8021     8025       +4     
==========================================
+ Hits         5489     6050     +561     
+ Misses       2110     1589     -521     
+ Partials      422      386      -36     

Impacted Files	Coverage Δ
x/leverage/types/msgs.go	100.00% <100.00%> (+90.90%)	⬆️
x/leverage/types/params.go	98.21% <100.00%> (+75.69%)	⬆️

... and 10 files with indirect coverage changes

[toteki]

Good work - I left a couple comments but it should be good to merge overall