IO Retry tests

LanguageExt.Tests/IOTests/RetryTests.cs

@@ -0,0 +1,120 @@
+using System;
+using System.Threading.Tasks;
+using Xunit;
+
+namespace LanguageExt.Tests.IOTests;
+
+public class RetryTests
+{
+    [Fact]
+    public void Retry_SuccessOnFirstAttempt_ShouldReturnResultImmediately()
+    {
+        var io = IO.lift(() => 42);
+        var schedule = Schedule.Never;
+        var retryableIO = io.Retry(schedule);
+
+        var result = retryableIO.Run();
+
+        Assert.Equal(42, result);
+    }
+
+    [Fact]
+    public void Retry_FailingThenSuccess_ShouldRetryAndReturnSuccess()
+    {
+        var attempt = 0;
+        var io = IO.lift(() =>
+        {
+            attempt++;
+            if (attempt < 3) throw new Exception($"Failure {attempt}");
+            return 42;
+        });
+
+        var schedule = Schedule.recurs(2);
+        var retryableIO = io.Retry(schedule);
+
+        var result = retryableIO.Run();
+
+        Assert.Equal(42, result);
+        Assert.Equal(3, attempt);
+    }
+
+    [Fact]
+    public void Retry_ExceedsMaxRetry_ShouldThrowLastError()
+    {
+        var io = IO.lift<int>(() => throw new Exception("Persistent failure"));
+        var schedule = Schedule.recurs(2);
+        var retryableIO = io.Retry(schedule);
+
+        Assert.ThrowsAny<Exception>(() => retryableIO.Run());
+    }
+
+    [Fact]
+    public void RetryWhile_ShouldContinueWhilePredicateIsTrue()
+    {
+        var attempt = 0;
+        var io = IO.lift<int>(() =>
+        {
+            attempt++;
+            throw new Exception($"Failure {attempt}");
+        });
+
+        var retryableIO = io.RetryWhile(error => error.Message.Contains("Failure 1") || error.Message.Contains("Failure 2"));
+
+        Assert.ThrowsAny<Exception>(() => retryableIO.Run());
+
+        Assert.Equal(3, attempt);
+    }
+
+    [Fact]
+    public void RetryUntil_ShouldStopWhenPredicateReturnsTrue()
+    {
+        var attempt = 0;
+        var io = IO.lift<int>(() =>
+        {
+            attempt++;
+            throw new Exception($"Failure {attempt}");
+        });
+
+        var retryableIO = io.RetryUntil(error => error.Message.Contains("Failure 2"));
+
+        Assert.ThrowsAny<Exception>(() => retryableIO.Run());
+
+        Assert.Equal(2, attempt);
+    }
+
+    [Fact]
+    public void RetryWithSchedule_Spaced_ShouldRespectIntervalsAndStopAfterScheduleExpires()
+    {
+        var attempt = 0;
+        var io = IO.lift<int>(() =>
+        {
+            attempt++;
+            throw new Exception($"Failure {attempt}");
+        });
+
+        var schedule    = Schedule.spaced(new Duration(100)).Take(3);
+        var retryableIO = io.Retry(schedule);
+
+        Assert.ThrowsAny<Exception>(() => retryableIO.Run());
+
+        Assert.Equal(4, attempt);
+    }
+
+    [Fact]
+    public void RetryWithSchedule_ExponentialBackoff_ShouldRetryWithIncreasingIntervals()
+    {
+        var attempt = 0;
+        var io = IO.lift<int>(() =>
+        {
+            attempt++;
+            throw new Exception($"Failure {attempt}");
+        });
+
+        var schedule = Schedule.exponential(new Duration(100)).Take(3);
+        var retryableIO = io.Retry(schedule);
+
+        Assert.ThrowsAny<Exception>(() => retryableIO.Run());
+
+        Assert.Equal(4, attempt);
+    }
+}