ceph-volume: data_allocate_fraction: arg_validators tests

Add tests for argument validator. Check for Nan, <=0.0 and > 1.0

Signed-off-by: Jonas Pfefferle <pepperjo@japf.ch>

src/ceph-volume/ceph_volume/tests/util/test_arg_validators.py

@@ -87,3 +87,30 @@ class TestValidDevice(object):
     def test_path_is_invalid(self, fake_call):
         with pytest.raises(argparse.ArgumentError):
             self.validator('/device/does/not/exist')
+
+
+class TestValidFraction(object):
+
+    def setup(self):
+        self.validator = arg_validators.ValidFraction()
+
+    def test_fraction_is_valid(self, fake_call):
+        result = self.validator('0.8')
+        assert result == 0.8
+
+    def test_fraction_is_nan(self, fake_call):
+        with pytest.raises(argparse.ArgumentError):
+            self.validator('NaN')
+
+    def test_fraction_is_negative(self, fake_call):
+        with pytest.raises(argparse.ArgumentError):
+            self.validator('-1.0')
+
+    def test_fraction_is_zero(self, fake_call):
+        with pytest.raises(argparse.ArgumentError):
+            self.validator('0.0')
+
+    def test_fraction_is_greater_one(self, fake_call):
+        with pytest.raises(argparse.ArgumentError):
+            self.validator('1.1')
+