diff --git a/src/scope/tests/test_utils.py b/src/scope/tests/test_utils.py
index 9054d4c..72c6d47 100644
--- a/src/scope/tests/test_utils.py
+++ b/src/scope/tests/test_utils.py
@@ -185,3 +185,59 @@ def test_gaussian_shifted_blue(self):
         wav_max_shifted = eval_wave[np.argmax(shifted_flux)]
         wav_max = eval_wave[np.argmax(interped_flux)]
         assert wav_max_shifted < wav_max
+
+
+class TestCrossingTime(unittest.TestCase):
+    """
+    tests the exposure time calculation.
+    """
+
+    period = 1.80988198
+    mstar = 1.458
+    e = 0.000
+    inc = 89.623
+    mplanet = 0.894
+    rstar = 1.756
+    peri = 0
+    b = 0.027
+    R = 45000
+    pix_per_res = 3.3
+    plot = False
+
+    def test_crossing_time_moremassive_star(self):
+        """
+        in a greater potential well, the crossing time is shorter.
+        """
+        low_mass_time, _, _, _ = calc_crossing_time()
+
+        high_mass_time, _, _, _ = calc_crossing_time(mstar=10 * self.mstar)
+        assert low_mass_time > high_mass_time
+
+    def test_crossing_time_moremassive_star(self):
+        """
+        on a longer period for the same star, the crossing time is longer.
+        """
+        short_period_time, _, _, _ = calc_crossing_time()
+
+        long_period_time, _, _, _ = calc_crossing_time(period=10 * self.period)
+        assert short_period_time < long_period_time
+
+    def test_crossing_time_pixel_per_res(self):
+        """
+        more pixels per resolution element, shorter time to cross the pixels.
+        """
+        _, few_pixels_per_element, _, _ = calc_crossing_time()
+
+        _, many_pixels_per_element, _, _ = calc_crossing_time(
+            pix_per_res=10 * self.pix_per_res
+        )
+        assert many_pixels_per_element < few_pixels_per_element
+
+    def test_crossing_time_resolution(self):
+        """
+        higher resolution, shorter crossing time.
+        """
+        low_resolution_time, _, _, _ = calc_crossing_time()
+
+        high_resolution_time, _, _, _ = calc_crossing_time(R=10 * self.R)
+        assert high_resolution_time < low_resolution_time
diff --git a/src/scope/utils.py b/src/scope/utils.py
index b865411..f15c7cc 100644
--- a/src/scope/utils.py
+++ b/src/scope/utils.py
@@ -205,7 +205,7 @@ def calc_doppler_shift(eval_wave, template_wave, template_flux, v):
     return shifted_flux
 
 
-def calc_exposure_time(
+def calc_crossing_time(
     period=1.80988198,
     mstar=1.458,
     e=0.000,