add unit test with the original problem.

tests/test_pixel.py

@@ -21,7 +21,6 @@
 import time
 import os
 import fitsio
-import copy
 
 from piff_test_helper import get_script_name, timer, CaptureLog
 
@@ -1790,6 +1789,83 @@ def test_convert_func():
         print('fitted params = ',star1.fit.params)
         np.testing.assert_allclose(star1.fit.params, model_im.array.ravel(), rtol=2.e-3)
 
+@timer
+def test_convergence_centering_failed():
+
+    # Before https://rubinobs.atlassian.net/browse/DM-49152, it was
+    # running an infinite number of time. Reason is because fitting center
+    # looks to fail in some cases. So now it should converge if center fail.
+    # It should converged now and exclude properly stars that were not
+    # able to be get a good center fit and then being reflux. If centering,
+    # is fixed, this test might need to be removed.
+
+    piffConfig = {
+        'type': 'Simple',
+        'model': {
+            'type': 'PixelGrid',
+            'scale': 0.2,
+            'size': 25,
+            'interp': 'Lanczos(11)'
+        },
+        'interp': {
+            'type': 'BasisPolynomial',
+            'order': 1,
+            'solver': 'scipy'
+        },
+        'outliers': {
+            'type': 'Chisq',
+            'nsigma': 4.0,
+            'max_remove': 0.05
+        },
+        'max_iter': 30
+    }
+
+    starData = fitsio.read('input/testStarsRubin.fits')
+    image = starData["IMAGE"][0]
+    weight = starData["WEIGHT"][0]
+    x = starData["X"][0]
+    y = starData["Y"][0]
+    xmin = starData["XMIN"][0]
+    xmax = starData["XMAX"][0]
+    ymin = starData["YMIN"][0]
+    ymax = starData["YMAX"][0]
+
+    nstars = len(x)
+    stars = []
+
+    gswcs = galsim.PixelScale(0.20038369063248057)
+    wcs = {0: gswcs}
+    pointing = None
+
+    stars = []
+
+    for i in range(nstars):
+
+        bds = galsim.BoundsI(
+                    galsim.PositionI(xmin[i], ymin[i]),
+                    galsim.PositionI(xmax[i], ymax[i])
+                )
+        gsImage = galsim.Image(bds, wcs=gswcs, dtype=float)
+        gsImage.array[:] = image[i]
+
+        gsWeight = galsim.Image(bds, wcs=gswcs, dtype=float)
+        gsWeight.array[:] = weight[i]
+
+        image_pos = galsim.PositionD(x[i], y[i])
+        data = piff.StarData(
+            gsImage,
+            image_pos,
+            weight=gsWeight,
+            pointing=pointing
+        )
+        stars.append(piff.Star(data, None))
+
+
+    piffResult = piff.PSF.process(piffConfig)
+    piffResult.fit(stars, wcs, pointing)
+
+    assert piffResult.niter == 6, 'Maximum number of iterations in this example must be 6.'
+    assert np.shape(piffResult.stars[28].fit.A) == (0, 625), 'Centroid failed for this star, expected shape of A is (0,625)'
 
 if __name__ == '__main__':
     #import cProfile, pstats