Catch up to upstream Java 0.21 release

Author: paulirwin

src/F23.StringSimilarity/NGram.cs

@@ -56,6 +56,11 @@ public double Distance(string s0, string s1)
             int sl = s0.Length;
             int tl = s1.Length;
 
+            if (s0.Equals(s1))
+            {
+                return 0;
+            }
+
             if (sl == 0 || tl == 0)
             {
                 if (sl == tl)

test/F23.StringSimilarity.Tests/NGramTest.cs

@@ -14,6 +14,26 @@ public void TestDistance()
             var ngram = new NGram();
 
             Assert.True(ngram.Distance(s0, s1) < ngram.Distance(s0, s2));
+
+            Assert.Equal(
+                expected: 0.0,
+                actual: ngram.Distance("SIJK", "SIJK"),
+                precision: 1); // 0.0
+
+            Assert.Equal(
+                expected: 0.0,
+                actual: ngram.Distance("S", "S"),
+                precision: 1); // 0.0
+
+            Assert.Equal(
+                expected: 1.0,
+                actual: ngram.Distance("", "S"),
+                precision: 1); // 0.0
+
+            Assert.Equal(
+                expected: 1.0,
+                actual: ngram.Distance("", "SIJK"),
+                precision: 1); // 0.0
         }
     }
 }

test/F23.StringSimilarity.Tests/QGramTest.cs

@@ -23,6 +23,7 @@
  */
 
 
+using System;
 using System.Diagnostics.CodeAnalysis;
 using Xunit;
 
@@ -45,6 +46,16 @@ public void TestDistance()
             var result = instance.Distance("ABCD", "ABCE");
 
             Assert.Equal(expected: 2.0, actual: result);
+
+            Assert.Equal(
+                expected: 0.0,
+                actual: instance.Distance("S", "S"),
+                precision: 1); // 0.0
+
+            Assert.Equal(
+                expected: 0.0,
+                actual: instance.Distance("012345", "012345"),
+                precision: 1); // 0.0
         }
     }
 }