Enhance [EditText] tests

[hyochan]

Description

As [Button] tests are refactored in #375, I've applied similar changes to [EditText]. These changes are going to apply to every refactored component from now.

Tests

Enhance tests in [EditText] with all scenarios covered.

Checklist

Before you create this PR confirms that it meets all requirements listed below by checking the relevant checkboxes ([x]). This will ensure a smooth and quick review process.

• [x] I read the Contributor Guide and followed the process outlined there for submitting PRs.
• [x] Run yarn test or yarn test -u if you need to update snapshot.
• [x] Run yarn lint
• [x] I am willing to follow-up on review comments in a timely manner.

[codecov[bot]]

Codecov Report

Merging #376 (8d6b322) into master (77f4597) will increase coverage by 0.65%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #376      +/-   ##
==========================================
+ Coverage   73.44%   74.10%   +0.65%     
==========================================
  Files          36       36              
  Lines         919      919              
  Branches      256      256              
==========================================
+ Hits          675      681       +6     
  Misses        188      188              
+ Partials       56       50       -6