diff --git a/scikits/image/io/tests/test_colormixer.py b/scikits/image/io/tests/test_colormixer.py
new file mode 100644
index 00000000..6ea620eb
--- /dev/null
+++ b/scikits/image/io/tests/test_colormixer.py
@@ -0,0 +1,49 @@
+from numpy.testing import *
+import numpy as np
+
+import scikits.image.io._plugins._colormixer as cm
+
+class ColorMixerTest(object):
+    def setup(self):
+        self.state = np.ones((18, 33, 3), dtype=np.uint8) * 200
+        self.img = np.zeros_like(self.state)
+
+    def test_basic(self):
+        self.op(self.img, self.state, 0, self.positive)
+        assert_array_equal(self.img[..., 0],
+                           self.py_op(self.state[..., 0], self.positive))
+
+    def test_clip(self):
+        self.op(self.img, self.state, 0, self.positive_clip)
+        assert_array_equal(self.img[..., 0],
+                           np.ones_like(self.img[..., 0]) * 255)
+
+    def test_negative(self):
+        self.op(self.img, self.state, 0, self.negative)
+        assert_array_equal(self.img[..., 0],
+                           self.py_op(self.state[..., 0], self.negative))
+
+    def test_negative_clip(self):
+        self.op(self.img, self.state, 0, self.negative_clip)
+        assert_array_equal(self.img[..., 0],
+                           np.zeros_like(self.img[..., 0]))
+
+class TestColorMixerAdd(ColorMixerTest):
+    op = cm.add
+    py_op = np.add
+    positive = 50
+    positive_clip = 56
+    negative = -50
+    negative_clip = -220
+
+class TestColorMixerMul(ColorMixerTest):
+    op = cm.multiply
+    py_op = np.multiply
+    positive = 1.2
+    positive_clip = 2
+    negative = 0.5
+    negative_clip = -0.5
+
+
+if __name__ == "__main__":
+    run_module_suite()