Add T.RepeatValue(int)

X10D.Tests/src/Core/CoreTests.cs

@@ -1,4 +1,4 @@
-using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
 using X10D.Core;
 
 namespace X10D.Tests.Core;
@@ -49,5 +49,28 @@ public class CoreTests
         Assert.IsNotNull(enumerable);
         Assert.AreEqual(o, enumerable.ElementAt(0));
     }
+
+    [TestMethod]
+    [DataRow(1)]
+    [DataRow("f")]
+    [DataRow(true)]
+    public void RepeatValue_ShouldContainRepeatedValue_GivenValue(object o)
+    {
+        IEnumerable<object> enumerable = o.RepeatValue(10);
+        Assert.IsNotNull(enumerable);
+
+        object[] array = enumerable.ToArray();
+        Assert.AreEqual(10, array.Length);
+        CollectionAssert.AreEqual(new[] {o, o, o, o, o, o, o, o, o, o}, array);
+    }
+
+    [TestMethod]
+    [DataRow(1)]
+    [DataRow("f")]
+    [DataRow(true)]
+    public void RepeatValue_ShouldThrow_GivenNegativeCount(object o)
+    {
+        // we must force enumeration via ToArray() to ensure the exception is thrown
+        Assert.ThrowsException<ArgumentOutOfRangeException>(() => o.RepeatValue(-1).ToArray());
     }
 }

X10D/src/Core/Extensions.cs

@@ -1,4 +1,4 @@
-namespace X10D.Core;
+namespace X10D.Core;
 
 /// <summary>
 ///     Extension methods which apply to all types.
@@ -30,4 +30,25 @@ public static class Extensions
     {
         yield return value;
     }
+
+    /// <summary>
+    ///     Returns an enumerable collection containing the current value repeated a specified number of times.
+    /// </summary>
+    /// <param name="value">The value to repeat.</param>
+    /// <param name="count">The number of times to repeat <paramref name="value" />.</param>
+    /// <typeparam name="T">The type of <paramref name="value"/>.</typeparam>
+    /// <returns>An enumerable collection containing <paramref name="value" /> repeated <paramref name="count" /> times.</returns>
+    /// <exception cref="ArgumentOutOfRangeException"><paramref name="count" /> is less than 0.</exception>
+    public static IEnumerable<T> RepeatValue<T>(this T value, int count)
+    {
+        if (count < 0)
+        {
+            throw new ArgumentOutOfRangeException(nameof(count), ExceptionMessages.CountMustBeGreaterThanOrEqualTo0);
+        }
+
+        for (var i = 0; i < count; i++)
+        {
+            yield return value;
+        }
+    }
 }