svrnty-mcp-gateway/tests/Svrnty.MCP.Gateway.Core.Tests/Interfaces/IRoutingStrategyTests.cs

using Xunit;
using Moq;
using Svrnty.MCP.Gateway.Core.Interfaces;
using Svrnty.MCP.Gateway.Core.Models;

namespace Svrnty.MCP.Gateway.Core.Tests.Interfaces;

/// <summary>
/// Unit tests for IRoutingStrategy interface following TDD approach.
/// Tests server selection logic.
/// </summary>
public class IRoutingStrategyTests
{
    [Fact]
    public async Task SelectServerAsync_WithHealthyServers_ReturnsServer()
    {
        // Arrange
        var mockStrategy = new Mock<IRoutingStrategy>();
        var servers = new List<ServerInfo>
        {
            new ServerInfo { Id = "server-1", IsHealthy = true },
            new ServerInfo { Id = "server-2", IsHealthy = true }
        };
        var context = new RoutingContext { ToolName = "test_tool" };

        mockStrategy
            .Setup(s => s.SelectServerAsync(
                It.IsAny<IEnumerable<ServerInfo>>(),
                It.IsAny<RoutingContext>(),
                It.IsAny<CancellationToken>()))
            .ReturnsAsync(servers[0]);

        // Act
        var selected = await mockStrategy.Object.SelectServerAsync(servers, context, CancellationToken.None);

        // Assert
        Assert.NotNull(selected);
        Assert.Equal("server-1", selected.Id);
        mockStrategy.Verify(s => s.SelectServerAsync(servers, context, It.IsAny<CancellationToken>()), Times.Once);
    }

    [Fact]
    public async Task SelectServerAsync_WithNoHealthyServers_ReturnsNull()
    {
        // Arrange
        var mockStrategy = new Mock<IRoutingStrategy>();
        var servers = new List<ServerInfo>
        {
            new ServerInfo { Id = "server-1", IsHealthy = false },
            new ServerInfo { Id = "server-2", IsHealthy = false }
        };
        var context = new RoutingContext { ToolName = "test_tool" };

        mockStrategy
            .Setup(s => s.SelectServerAsync(
                It.IsAny<IEnumerable<ServerInfo>>(),
                It.IsAny<RoutingContext>(),
                It.IsAny<CancellationToken>()))
            .ReturnsAsync((ServerInfo?)null);

        // Act
        var selected = await mockStrategy.Object.SelectServerAsync(servers, context, CancellationToken.None);

        // Assert
        Assert.Null(selected);
    }

    [Fact]
    public async Task SelectServerAsync_WithRoutingContext_UsesContext()
    {
        // Arrange
        var mockStrategy = new Mock<IRoutingStrategy>();
        var servers = new List<ServerInfo>
        {
            new ServerInfo { Id = "server-1", IsHealthy = true }
        };
        var context = new RoutingContext
        {
            ToolName = "specific_tool",
            ClientId = "client-123",
            Metadata = new Dictionary<string, object> { { "region", "us-east" } }
        };

        mockStrategy
            .Setup(s => s.SelectServerAsync(
                It.IsAny<IEnumerable<ServerInfo>>(),
                It.Is<RoutingContext>(c => c.ToolName == "specific_tool"),
                It.IsAny<CancellationToken>()))
            .ReturnsAsync(servers[0]);

        // Act
        var selected = await mockStrategy.Object.SelectServerAsync(servers, context, CancellationToken.None);

        // Assert
        Assert.NotNull(selected);
        mockStrategy.Verify(s => s.SelectServerAsync(
            It.IsAny<IEnumerable<ServerInfo>>(),
            It.Is<RoutingContext>(c => c.ToolName == "specific_tool"),
            It.IsAny<CancellationToken>()), Times.Once);
    }

    [Fact]
    public async Task SelectServerAsync_WithEmptyServerList_ReturnsNull()
    {
        // Arrange
        var mockStrategy = new Mock<IRoutingStrategy>();
        var servers = new List<ServerInfo>();
        var context = new RoutingContext { ToolName = "test_tool" };

        mockStrategy
            .Setup(s => s.SelectServerAsync(
                It.IsAny<IEnumerable<ServerInfo>>(),
                It.IsAny<RoutingContext>(),
                It.IsAny<CancellationToken>()))
            .ReturnsAsync((ServerInfo?)null);

        // Act
        var selected = await mockStrategy.Object.SelectServerAsync(servers, context, CancellationToken.None);

        // Assert
        Assert.Null(selected);
    }
}