From b1fb5a3673549920d47da01154ffb4ba0407e0a7 Mon Sep 17 00:00:00 2001
From: Kyle Conroy <kyleconroy@gmail.com>
Date: Wed, 23 Mar 2022 12:10:38 -0400
Subject: [PATCH] add tests

---
 specreduce/tests/test_background.py | 43 +++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)
 create mode 100644 specreduce/tests/test_background.py

diff --git a/specreduce/tests/test_background.py b/specreduce/tests/test_background.py
new file mode 100644
index 00000000..2b914334
--- /dev/null
+++ b/specreduce/tests/test_background.py
@@ -0,0 +1,43 @@
+import numpy as np
+
+import astropy.units as u
+from astropy.nddata import CCDData
+
+from specreduce.background import Background
+from specreduce.tracing import FlatTrace
+
+
+# Test image is comprised of 30 rows with 10 columns each. Row content
+# is row index itself. This makes it easy to predict what should be the
+# value extracted from a region centered at any arbitrary Y position.
+image = np.ones(shape=(30, 10))
+for j in range(image.shape[0]):
+    image[j, ::] *= j
+image = CCDData(image, unit=u.Jy)
+
+
+def test_background():
+    #
+    # Try combinations of extraction center, and even/odd
+    # extraction aperture sizes.
+    #
+    trace_pos = 15.0
+    trace = FlatTrace(image, trace_pos)
+    bkg_sep = 5
+    bkg_width = 2
+    # all the following should be equivalent:
+    bg1 = Background(image, [trace-bkg_sep, trace+bkg_sep], width=bkg_width)
+    bg2 = Background.two_sided(image, trace, bkg_sep, width=bkg_width)
+    bg3 = Background.two_sided(image, trace_pos, bkg_sep, width=bkg_width)
+    assert np.allclose(bg1.bkg_array, bg2.bkg_array)
+    assert np.allclose(bg1.bkg_array, bg3.bkg_array)
+
+    # test that creating a one_sided background works
+    Background.one_sided(image, trace, bkg_sep, width=bkg_width)
+
+    # test that image subtraction works
+    sub1 = image - bg1
+    sub2 = bg1.sub_image(image)
+    sub3 = bg1.sub_image()
+    assert np.allclose(sub1, sub2)
+    assert np.allclose(sub1, sub3)