feat: add resilient reconnect and catch-up replay

tests/SuiteLink.Client.Tests/Internal/SuiteLinkRetryDelayCalculatorTests.cs

@@ -0,0 +1,52 @@
+using SuiteLink.Client.Internal;
+
+namespace SuiteLink.Client.Tests.Internal;
+
+public sealed class SuiteLinkRetryDelayCalculatorTests
+{
+    [Fact]
+    public void GetDelay_UsesImmediateThenExponentialCap()
+    {
+        var policy = new SuiteLinkRetryPolicy(
+            initialDelay: TimeSpan.FromSeconds(1),
+            multiplier: 2.0,
+            maxDelay: TimeSpan.FromSeconds(30),
+            useJitter: false);
+
+        Assert.Equal(TimeSpan.Zero, SuiteLinkRetryDelayCalculator.GetDelay(policy, 0));
+        Assert.Equal(TimeSpan.FromSeconds(1), SuiteLinkRetryDelayCalculator.GetDelay(policy, 1));
+        Assert.Equal(TimeSpan.FromSeconds(2), SuiteLinkRetryDelayCalculator.GetDelay(policy, 2));
+        Assert.Equal(TimeSpan.FromSeconds(4), SuiteLinkRetryDelayCalculator.GetDelay(policy, 3));
+    }
+
+    [Theory]
+    [InlineData(-1, 2.0, 30)]
+    [InlineData(1, 0.0, 30)]
+    [InlineData(1, -1.0, 30)]
+    [InlineData(1, 2.0, -1)]
+    public void RetryPolicy_InvalidArguments_Throw(
+        int initialDelaySeconds,
+        double multiplier,
+        int maxDelaySeconds)
+    {
+        Assert.ThrowsAny<ArgumentOutOfRangeException>(() => new SuiteLinkRetryPolicy(
+            initialDelay: TimeSpan.FromSeconds(initialDelaySeconds),
+            multiplier: multiplier,
+            maxDelay: TimeSpan.FromSeconds(maxDelaySeconds),
+            useJitter: false));
+    }
+
+    [Fact]
+    public void GetDelay_WithJitterEnabled_StaysWithinCap()
+    {
+        var policy = new SuiteLinkRetryPolicy(
+            initialDelay: TimeSpan.FromSeconds(2),
+            multiplier: 2.0,
+            maxDelay: TimeSpan.FromSeconds(10),
+            useJitter: true);
+
+        var delay = SuiteLinkRetryDelayCalculator.GetDelay(policy, 3, () => 0.5);
+
+        Assert.InRange(delay, TimeSpan.Zero, TimeSpan.FromSeconds(10));
+    }
+}