diff --git a/scikits/image/io/tests/test_colormixer.py b/scikits/image/io/_plugins/tests/test_colormixer.py
similarity index 100%
rename from scikits/image/io/tests/test_colormixer.py
rename to scikits/image/io/_plugins/tests/test_colormixer.py
diff --git a/scikits/image/io/_plugins/tests/test_histograms.py b/scikits/image/io/_plugins/tests/test_histograms.py
new file mode 100644
index 00000000..f1cbe1c5
--- /dev/null
+++ b/scikits/image/io/_plugins/tests/test_histograms.py
@@ -0,0 +1,16 @@
+from numpy.testing import *
+import numpy as np
+
+import scikits.image.io._plugins._colormixer as cm
+from scikits.image.io._plugins._histograms import histograms
+
+class TestHistogram:
+    def test_basic(self):
+        img = np.ones((50, 50, 3), dtype=np.uint8)
+        r, g, b, v = histograms(img, 255)
+
+        for band in (r, g, b, v):
+            yield assert_equal, band.sum(), 50*50
+
+if __name__ == "__main__":
+    run_module_suite()