Add test for limiting magnitude estimate

tests/models/test_measurements.py

@@ -83,7 +83,31 @@ def test_measurements_attributes(measurer, ptf_datastore, test_config):
     m.flux_apertures[m.best_aperture] = original_flux
     new_im.zp.dzp = original_zp_err
 
-    # TODO: add test for limiting magnitude (issue #143)
+    #test for limiting magnitude
+    srcList = ptf_datastore.sources
+    limMagEst, snrs, mags, grad, intercept = srcList.estimate_lim_mag(aperture=1)
+
+    #Skip the lim mag test if using PSF photometry (i.e. if limMagEst==None)
+    if limMagEst != None:
+        #if interactive testing enabled, make and save a Magnitude vs SNR plot
+        if os.getenv('INTERACTIVE') is not None: 
+            xdata = np.linspace(np.log(3),np.log(20),1000)
+            plt.plot(snrs,mags,linewidth=0,marker='o',c='midnightblue')
+            plt.plot(xdata, grad * xdata + intercept, c='firebrick')
+            plt.xlabel('log SNR')
+            plt.ylabel('magnitude')
+            plt.title('Limiting magntiude = {:.2f} mag'.format(limMagEst))
+            ymin,ymax = plt.gca().get_ylim()
+            plt.vlines(x=np.log(5),ymin=ymin,ymax=ymax)
+            plt.hlines(y=limMagEst,xmin=np.log(3),xmax=np.log(20))
+            plt.xlim(np.log(3),np.log(20))
+            plt.ylim(ymin,ymax)
+            plt.savefig('plots/snr_mag_plot.png')
+            plt.show()
+
+        #check the limiting magnitude is consistent with previous runs
+        assert limMagEst == pytest.approx(20.668, abs=0.05)
+
 
 
 def test_filtering_measurements(ptf_datastore):