add minimal unit test for reflected-light functionality

tests/test_brightness.py

@@ -0,0 +1,40 @@
+"""
+Tests for the reflected-light calculation in system.compute_all_orbits
+"""
+
+from orbitize import system
+from orbitize import DATADIR, read_input
+import os
+import numpy as np
+
+
+def test_brightness_calculation():
+
+    num_secondary_bodies = 1
+    input_file = os.path.join(DATADIR, "GJ504.csv")
+    data_table = read_input.read_file(input_file)
+    system_mass = 1.47
+    plx = 24.30
+
+    test_system = system.System(num_secondary_bodies, data_table, system_mass, plx)
+
+    params = np.array(
+        [
+            7.2774010e01,
+            4.1116819e-02,
+            5.6322372e-01,
+            3.5251172e00,
+            4.2904768e00,
+            9.4234377e-02,
+            4.5418411e01,
+            1.4317369e-03,
+            5.6322372e-01,
+            3.1016846e00,
+            4.2904768e00,
+            3.4033456e-01,
+            2.4589758e01,
+            1.4849439e00,
+        ]
+    )
+
+    ra, dec, vz, brightness = test_system.compute_all_orbits(params)