DM-10454: Add check that science and template have matching bands.

python/lsst/ip/diffim/subtractImages.py

@@ -695,8 +695,8 @@ def _calculateMagLim(self, exposure, nsigma=5.0, fallbackPsfSize=None):
 
     @staticmethod
     def _validateExposures(template, science):
-        """Check that the WCS of the two Exposures match, and the template bbox
-        contains the science bbox.
+        """Check that the WCS of the two Exposures match, the template bbox
+        contains the science bbox, and that the bands match.
 
         Parameters
         ----------
@@ -709,13 +709,16 @@ def _validateExposures(template, science):
         ------
         AssertionError
             Raised if the WCS of the template is not equal to the science WCS,
-            or if the science image is not fully contained in the template
-            bounding box.
+            if the science image is not fully contained in the template
+            bounding box, or if the bands do not match.
         """
         assert template.wcs == science.wcs, \
             "Template and science exposure WCS are not identical."
         templateBBox = template.getBBox()
         scienceBBox = science.getBBox()
+        assert science.filter.bandLabel == template.filter.bandLabel, \
+            "Science and template exposures have different bands: %s, %s" % \
+            (science.filter, template.filter)
 
         assert templateBBox.contains(scienceBBox), \
             "Template bbox does not contain all of the science image."

python/lsst/ip/diffim/utils.py

@@ -1139,6 +1139,8 @@ def makeTestImage(seed=5, nSrc=20, psfSize=2., noiseLevel=5.,
                   flux=None,
                   clearEdgeMask=False,
                   addMaskPlanes=None,
+                  band="g",
+                  physicalFilter="g NotACamera"
                   ):
     """Make a reproduceable PSF-convolved exposure for testing.
 
@@ -1243,6 +1245,7 @@ def makeTestImage(seed=5, nSrc=20, psfSize=2., noiseLevel=5.,
     if background is not None:
         modelExposure.image += background
     modelExposure.maskedImage /= calibration
+    modelExposure.setFilter(afwImage.FilterLabel(band, physicalFilter))
     modelExposure.info.setId(seed)
     if doApplyCalibration:
         modelExposure.maskedImage = modelExposure.photoCalib.calibrateImage(modelExposure.maskedImage)

tests/test_subtractTask.py

@@ -64,6 +64,21 @@ def test_mismatched_template(self):
         with self.assertRaises(AssertionError):
             task.run(template, science, sources)
 
+    def test_mismatched_filter(self):
+        """Test that an error is raised if the science and template have
+        different bands.
+        """
+        xSize = 200
+        ySize = 200
+        science, sources = makeTestImage(psfSize=2.4, xSize=xSize + 20, ySize=ySize + 20,
+                                         band="g", physicalFilter="g noCamera")
+        template, _ = makeTestImage(psfSize=2.4, xSize=xSize, ySize=ySize, doApplyCalibration=True,
+                                    band="not-g", physicalFilter="not-g noCamera")
+        config = subtractImages.AlardLuptonSubtractTask.ConfigClass()
+        task = subtractImages.AlardLuptonSubtractTask(config=config)
+        with self.assertRaises(AssertionError):
+            task.run(template, science, sources)
+
     def test_incomplete_template_coverage(self):
         noiseLevel = 1.
         border = 20