def test_otsu_coins_image_as_float():
    coins = skimage.img_as_float(data.coins())
    assert 0.41 < threshold_otsu(coins) < 0.42

def test_otsu_lena_image():
    assert threshold_otsu(data.lena()) == 141

def test_otsu_camera_image():
    assert threshold_otsu(data.camera()) == 87

def test_otsu_coins_image():
    assert threshold_otsu(data.coins()) == 107

 def test_otsu_negative_int(self):
     image = self.image - 2
     assert threshold_otsu(image) == 0

 def test_otsu_float_image(self):
     image = np.float64(self.image)
     assert 2 <= threshold_otsu(image) < 3

 def test_otsu(self):
     assert threshold_otsu(self.image) == 2

def test_otsu_camera_image():
    camera = skimage.img_as_ubyte(data.camera())
    assert 86 < threshold_otsu(camera) < 88

def test_otsu_lena_image():
    lena = skimage.img_as_ubyte(data.lena())
    assert 140 < threshold_otsu(lena) < 142

def test_otsu_coins_image():
    coins = skimage.img_as_ubyte(data.coins())
    assert 106 < threshold_otsu(coins) < 108

def test_otsu_astro_image():
    img = skimage.img_as_ubyte(data.astronaut())
    assert 109 < threshold_otsu(img) < 111