Fix #529

[ear7h]

Added fail tests for vm's REPL mode

[codecov]

Codecov Report

Merging #608 into master will increase coverage by 0.08%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #608      +/-   ##
==========================================
+ Coverage    82.9%   82.99%   +0.08%     
==========================================
  Files          55       55              
  Lines        7249     7249              
==========================================
+ Hits         6010     6016       +6     
+ Misses        992      988       -4     
+ Partials      247      245       -2

Impacted Files	Coverage Δ
vm/class.go	87.33% <0%> (+0.42%)	⬆️
vm/instruction.go	93.88% <0%> (+0.61%)	⬆️
vm/error.go	75.86% <0%> (+6.89%)	⬆️

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[st0012]

@ear7h Can you fix #584 with the test mechanism you built in this PR?

[ear7h]

@st0012 will do