[R-package] add assertions to test on lightgbm() weights (#5110)
[R-package] add assertions to test on lightgbm() weights (#5110)


henry0312/LightGBM,microsoft/LightGBM,microsoft/LightGBM,henry0312/LightGBM,henry0312/LightGBM,henry0312/LightGBM,microsoft/LightGBM,microsoft/LightGBM,microsoft/LightGBM,henry0312/LightGBM