Retaining duplicate X-axis values in a bar plot

Hi there, is it possible to retain x-axis values in a bar plot even if there are repeats? Pandas allows having index values with the same name in a dataframe, and so I have a dataframe like this:

data = {'test': [1, 2, 3]}
df = pd.DataFrame(data, index= ['a', 'b', 'a']

Then, if I make a bar plot with matplotlib using plt.bar(df['test'].index, df['test'].values), the resulting plot will contain only two bars - one on a and the other on b, whereas I expect three bars, one on each index. Any hints? Thanks for reading.