reference_image testing

Author: andrewrgarcia

tests/test_images/test_ema.png renamed to tests/reference_images/ema01.png

@@ -1,7 +1,23 @@
+import os
+import os.path
+import glob
 import mplfinance as mpf
 import pandas as pd   
+import matplotlib.pyplot as plt
+from   matplotlib.testing.compare import compare_images
 
-def test_ema():
+print('mpf.__version__ =',mpf.__version__)                 # for the record
+print('mpf.__file__ =',mpf.__file__)                       # for the record
+print("plt.rcParams['backend'] =",plt.rcParams['backend']) # for the record
+
+base='ema'
+tdir = os.path.join('tests','test_images')
+refd = os.path.join('tests','reference_images')
+
+IMGCOMP_TOLERANCE = 10.0  # this works fine for linux
+# IMGCOMP_TOLERANCE = 11.0  # required for a windows pass. (really 10.25 may do it).
+
+def create_ema_image(tname):
 
     df = pd.read_csv('./examples/data/yahoofinance-GOOG-20040819-20180120.csv', parse_dates=True)
     df.index = pd.DatetimeIndex(df['Date'])
@@ -20,8 +36,30 @@ def test_ema():
                          ylabel='calculated', secondary_y=False)
     ]
 
+    # plot and save in `tname` path
     mpf.plot(df, ylabel="mpf ema", type='ohlc',
-             ema=25, addplot=ap, panel_ratios=(1, 1)
+             ema=25, addplot=ap, panel_ratios=(1, 1), savefig=tname
     )
 
+
+def test_ema():
+
+    fname = base+'01.png'
+    tname = os.path.join(tdir,fname)
+    rname = os.path.join(refd,fname)
+
+    create_ema_image(tname)
+
+    tsize = os.path.getsize(tname)
+    print(glob.glob(tname),'[',tsize,'bytes',']')
+
+    rsize = os.path.getsize(rname)
+    print(glob.glob(rname),'[',rsize,'bytes',']')
+
+    result = compare_images(rname,tname,tol=IMGCOMP_TOLERANCE)
+    if result is not None:
+        print('result=',result)
+    assert result is None
+
+
 test_ema()