Generated string should contain only 0-9, a-Z characters (#131)

* make it work on MacOS

* Revert "make it work on MacOS"

This reverts commit dfa095d.

* generate string only which contain a-z, A-Z and 0-9 characters

src/benchmarks/Tests/UniqueValuesGeneratorTests.cs

@@ -45,5 +45,20 @@ private void AssertGeneratedArraysContainAlwaysSameValues<T>(int size)
                 Assert.Equal(generatedArray, anotherGeneratedArray);
             }
         }
+
+        [Fact]
+        public void GeneratedStringsContainOnlySimpleLettersAndDigits()
+        {
+            var strings = ValuesGenerator.ArrayOfUniqueValues<string>(1024);
+
+            foreach (var text in strings)
+            {
+                Assert.All(text, character => 
+                    Assert.True(
+                        char.IsDigit(character) 
+                        || (character >= 'a' && character <= 'z') 
+                        || (character >= 'A' && character <= 'Z')));
+            }
+        }
     }
 }

src/benchmarks/ValuesGenerator.cs

@@ -86,7 +86,16 @@ private static string GenerateRandomString(Random random, int minLength, int max
 
             var builder = new StringBuilder(length);
             for (int i = 0; i < length; i++)
-                builder.Append((char) random.Next(char.MinValue, char.MaxValue));
+            {
+                var rangeSelector = random.Next(0, 3);
+
+                if (rangeSelector == 0)
+                    builder.Append((char) random.Next('a', 'z'));
+                else if (rangeSelector == 1)
+                    builder.Append((char) random.Next('A', 'Z'));
+                else
+                    builder.Append((char) random.Next('0', '9'));
+            }
 
             return builder.ToString();
         }