diff --git a/skimage/feature/tests/test_blob.py b/skimage/feature/tests/test_blob.py
index 10167214..a46c442b 100644
--- a/skimage/feature/tests/test_blob.py
+++ b/skimage/feature/tests/test_blob.py
@@ -2,11 +2,13 @@ import numpy as np
 from skimage.draw import circle
 from skimage.feature import blob_dog, blob_log, blob_doh
 import math
+from numpy.testing import assert_raises
 
 
 def test_blob_dog():
     r2 = math.sqrt(2)
     img = np.ones((512, 512))
+    img3 = np.ones((5, 5, 5))
 
     xs, ys = circle(400, 130, 5)
     img[xs, ys] = 255
@@ -37,10 +39,13 @@ def test_blob_dog():
     assert abs(b[1] - 350) <= thresh
     assert abs(radius(b) - 45) <= thresh
 
+    assert_raises(ValueError, blob_dog, img3)
+
 
 def test_blob_log():
     r2 = math.sqrt(2)
     img = np.ones((512, 512))
+    img3 = np.ones((5, 5, 5))
 
     xs, ys = circle(400, 130, 5)
     img[xs, ys] = 255
@@ -80,9 +85,40 @@ def test_blob_log():
     assert abs(b[1] - 350) <= thresh
     assert abs(radius(b) - 30) <= thresh
 
+    # Testing log scale
+    blobs = blob_log(
+        img,
+        min_sigma=5,
+        max_sigma=20,
+        threshold=1,
+        log_scale=True)
+
+    b = s[0]
+    assert abs(b[0] - 400) <= thresh
+    assert abs(b[1] - 130) <= thresh
+    assert abs(radius(b) - 5) <= thresh
+
+    b = s[1]
+    assert abs(b[0] - 160) <= thresh
+    assert abs(b[1] - 50) <= thresh
+    assert abs(radius(b) - 15) <= thresh
+
+    b = s[2]
+    assert abs(b[0] - 100) <= thresh
+    assert abs(b[1] - 300) <= thresh
+    assert abs(radius(b) - 25) <= thresh
+
+    b = s[3]
+    assert abs(b[0] - 200) <= thresh
+    assert abs(b[1] - 350) <= thresh
+    assert abs(radius(b) - 30) <= thresh
+
+    assert_raises(ValueError, blob_log, img3)
+
 
 def test_blob_doh():
     img = np.ones((512, 512), dtype=np.uint8)
+    img3 = np.ones((5, 5, 5))
 
     xs, ys = circle(400, 130, 20)
     img[xs, ys] = 255
@@ -126,3 +162,53 @@ def test_blob_doh():
     assert abs(b[0] - 200) <= thresh
     assert abs(b[1] - 350) <= thresh
     assert abs(radius(b) - 50) <= thresh
+
+    # Testing log scale
+    blobs = blob_doh(
+        img,
+        min_sigma=1,
+        max_sigma=60,
+        num_sigma=10,
+        log_scale=True,
+        threshold=.05)
+
+    b = s[0]
+    assert abs(b[0] - 400) <= thresh
+    assert abs(b[1] - 130) <= thresh
+    assert abs(radius(b) - 20) <= thresh
+
+    b = s[1]
+    assert abs(b[0] - 460) <= thresh
+    assert abs(b[1] - 50) <= thresh
+    assert abs(radius(b) - 30) <= thresh
+
+    b = s[2]
+    assert abs(b[0] - 100) <= thresh
+    assert abs(b[1] - 300) <= thresh
+    assert abs(radius(b) - 40) <= thresh
+
+    b = s[3]
+    assert abs(b[0] - 200) <= thresh
+    assert abs(b[1] - 350) <= thresh
+    assert abs(radius(b) - 50) <= thresh
+
+    assert_raises(ValueError, blob_doh, img3)
+
+
+def test_blob_overlap():
+    img = np.ones((512, 512), dtype=np.uint8)
+
+    xs, ys = circle(100, 100, 20)
+    img[xs, ys] = 255
+
+    xs, ys = circle(120, 100, 30)
+    img[xs, ys] = 255
+
+    blobs = blob_doh(
+        img,
+        min_sigma=1,
+        max_sigma=60,
+        num_sigma=10,
+        threshold=.05)
+
+    assert len(blobs) == 1