Merge pull request #4 from paulirwin/master

Handle null and empty values in Jaro-Winkler

Author: jamesmblair

src/F23.StringSimilarity/JaroWinkler.cs

@@ -73,6 +73,11 @@ public JaroWinkler(double threshold)
          */
         public double Similarity(string s1, string s2)
         {
+            if (s1 == null) s1 = string.Empty;
+            if (s2 == null) s2 = string.Empty;
+
+            if (string.Equals(s1, s2)) return 1f;
+
             int[] mtp = Matches(s1, s2);
             float m = mtp[0];
             if (m == 0)

test/F23.StringSimilarity.Tests/JaroWinklerTest.cs

@@ -49,5 +49,17 @@ public void TestSimilarity()
                 precision: 6 // 0.000001
             );
         }
+
+        [Fact]
+        public void TestSimilarityBothEmpty()
+        {
+            var instance = new JaroWinkler();
+
+            Assert.Equal(
+                expected: 1,
+                actual: instance.Similarity(string.Empty, string.Empty),
+                precision: 6 // 0.000001
+            );
+        }
     }
 }