feat(backend): Implement MCP Protocol Handler (Story 5.1)
Implemented JSON-RPC 2.0 protocol handler for MCP communication, enabling AI agents to communicate with ColaFlow using the Model Context Protocol. **Implementation:** - JSON-RPC 2.0 data models (Request, Response, Error, ErrorCode) - MCP protocol models (Initialize, Capabilities, ClientInfo, ServerInfo) - McpProtocolHandler with method routing and error handling - Method handlers: initialize, resources/list, tools/list, tools/call - ASP.NET Core middleware for /mcp endpoint - Service registration and dependency injection setup **Testing:** - 28 unit tests covering protocol parsing, validation, and error handling - Integration tests for initialize handshake and error responses - All tests passing with >80% coverage **Changes:** - Created ColaFlow.Modules.Mcp.Contracts project - Created ColaFlow.Modules.Mcp.Domain project - Created ColaFlow.Modules.Mcp.Application project - Created ColaFlow.Modules.Mcp.Infrastructure project - Created ColaFlow.Modules.Mcp.Tests project - Registered MCP module in ColaFlow.API Program.cs - Added /mcp endpoint via middleware **Acceptance Criteria Met:** ✅ JSON-RPC 2.0 messages correctly parsed ✅ Request validation (jsonrpc: "2.0", method, params, id) ✅ Error responses conform to JSON-RPC 2.0 spec ✅ Invalid requests return proper error codes (-32700, -32600, -32601, -32602) ✅ MCP initialize method implemented ✅ Server capabilities returned (resources, tools, prompts) ✅ Protocol version negotiation works (1.0) ✅ Request routing to method handlers ✅ Unit test coverage > 80% ✅ All tests passing **Story**: docs/stories/sprint_5/story_5_1.md 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>
This commit is contained in:
Yaojia Wang
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using ColaFlow.Modules.Mcp.Application.Handlers;
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using ColaFlow.Modules.Mcp.Contracts.JsonRpc;
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using FluentAssertions;
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using Microsoft.Extensions.Logging;
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using NSubstitute;
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namespace ColaFlow.Modules.Mcp.Tests.Handlers;
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/// <summary>
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/// Unit tests for McpProtocolHandler
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/// </summary>
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public class McpProtocolHandlerTests
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{
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private readonly ILogger<McpProtocolHandler> _logger;
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private readonly List<IMcpMethodHandler> _methodHandlers;
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private readonly McpProtocolHandler _sut;
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public McpProtocolHandlerTests()
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{
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_logger = Substitute.For<ILogger<McpProtocolHandler>>();
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_methodHandlers = new List<IMcpMethodHandler>();
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_sut = new McpProtocolHandler(_logger, _methodHandlers);
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}
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[Fact]
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public async Task HandleRequestAsync_WithInvalidJsonRpc_ReturnsInvalidRequest()
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{
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// Arrange
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var request = new JsonRpcRequest
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{
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JsonRpc = "1.0", // Invalid version
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Method = "test"
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};
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// Act
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var response = await _sut.HandleRequestAsync(request, CancellationToken.None);
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// Assert
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response.Should().NotBeNull();
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response.JsonRpc.Should().Be("2.0");
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response.Error.Should().NotBeNull();
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response.Error!.Code.Should().Be((int)JsonRpcErrorCode.InvalidRequest);
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response.Result.Should().BeNull();
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}
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[Fact]
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public async Task HandleRequestAsync_WithMissingMethod_ReturnsInvalidRequest()
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{
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// Arrange
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var request = new JsonRpcRequest
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{
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JsonRpc = "2.0",
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Method = "" // Empty method
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};
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// Act
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var response = await _sut.HandleRequestAsync(request, CancellationToken.None);
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// Assert
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response.Should().NotBeNull();
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response.Error.Should().NotBeNull();
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response.Error!.Code.Should().Be((int)JsonRpcErrorCode.InvalidRequest);
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}
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[Fact]
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public async Task HandleRequestAsync_WithUnknownMethod_ReturnsMethodNotFound()
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{
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// Arrange
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var request = new JsonRpcRequest
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{
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JsonRpc = "2.0",
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Method = "unknown_method",
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Id = 1
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};
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// Act
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var response = await _sut.HandleRequestAsync(request, CancellationToken.None);
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// Assert
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response.Should().NotBeNull();
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response.JsonRpc.Should().Be("2.0");
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response.Id.Should().Be(1);
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response.Error.Should().NotBeNull();
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response.Error!.Code.Should().Be((int)JsonRpcErrorCode.MethodNotFound);
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response.Error.Message.Should().Contain("unknown_method");
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response.Result.Should().BeNull();
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}
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[Fact]
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public async Task HandleRequestAsync_WithValidMethod_ReturnsSuccess()
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{
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// Arrange
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var mockHandler = Substitute.For<IMcpMethodHandler>();
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mockHandler.MethodName.Returns("test_method");
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mockHandler.HandleAsync(Arg.Any<object?>(), Arg.Any<CancellationToken>())
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.Returns(Task.FromResult<object?>(new { result = "success" }));
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var handler = new McpProtocolHandler(_logger, new[] { mockHandler });
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var request = new JsonRpcRequest
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{
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JsonRpc = "2.0",
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Method = "test_method",
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Id = 1
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};
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// Act
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var response = await handler.HandleRequestAsync(request, CancellationToken.None);
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// Assert
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response.Should().NotBeNull();
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response.JsonRpc.Should().Be("2.0");
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response.Id.Should().Be(1);
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response.Error.Should().BeNull();
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response.Result.Should().NotBeNull();
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}
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[Fact]
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public async Task HandleRequestAsync_WhenHandlerThrowsArgumentException_ReturnsInvalidParams()
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{
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// Arrange
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var mockHandler = Substitute.For<IMcpMethodHandler>();
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mockHandler.MethodName.Returns("test_method");
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mockHandler.HandleAsync(Arg.Any<object?>(), Arg.Any<CancellationToken>())
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.Returns<object?>(_ => throw new ArgumentException("Invalid parameter"));
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var handler = new McpProtocolHandler(_logger, new[] { mockHandler });
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var request = new JsonRpcRequest
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{
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JsonRpc = "2.0",
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Method = "test_method",
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Id = 1
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};
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// Act
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var response = await handler.HandleRequestAsync(request, CancellationToken.None);
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// Assert
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response.Should().NotBeNull();
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response.Error.Should().NotBeNull();
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response.Error!.Code.Should().Be((int)JsonRpcErrorCode.InvalidParams);
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}
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[Fact]
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public async Task HandleRequestAsync_WhenHandlerThrowsException_ReturnsInternalError()
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{
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// Arrange
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var mockHandler = Substitute.For<IMcpMethodHandler>();
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mockHandler.MethodName.Returns("test_method");
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mockHandler.HandleAsync(Arg.Any<object?>(), Arg.Any<CancellationToken>())
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.Returns<object?>(_ => throw new InvalidOperationException("Something went wrong"));
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var handler = new McpProtocolHandler(_logger, new[] { mockHandler });
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var request = new JsonRpcRequest
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{
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JsonRpc = "2.0",
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Method = "test_method",
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Id = 1
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};
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// Act
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var response = await handler.HandleRequestAsync(request, CancellationToken.None);
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// Assert
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response.Should().NotBeNull();
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response.Error.Should().NotBeNull();
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response.Error!.Code.Should().Be((int)JsonRpcErrorCode.InternalError);
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}
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[Fact]
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public async Task HandleRequestAsync_WithStringId_PreservesIdInResponse()
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{
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// Arrange
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var mockHandler = Substitute.For<IMcpMethodHandler>();
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mockHandler.MethodName.Returns("test_method");
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mockHandler.HandleAsync(Arg.Any<object?>(), Arg.Any<CancellationToken>())
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.Returns(Task.FromResult<object?>(new { result = "success" }));
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var handler = new McpProtocolHandler(_logger, new[] { mockHandler });
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var request = new JsonRpcRequest
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{
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JsonRpc = "2.0",
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Method = "test_method",
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Id = "abc-123"
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};
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// Act
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var response = await handler.HandleRequestAsync(request, CancellationToken.None);
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// Assert
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response.Id.Should().Be("abc-123");
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}
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[Fact]
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public async Task HandleRequestAsync_WithParams_PassesParamsToHandler()
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{
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// Arrange
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var mockHandler = Substitute.For<IMcpMethodHandler>();
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mockHandler.MethodName.Returns("test_method");
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mockHandler.HandleAsync(Arg.Any<object?>(), Arg.Any<CancellationToken>())
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.Returns(Task.FromResult<object?>(new { result = "success" }));
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var handler = new McpProtocolHandler(_logger, new[] { mockHandler });
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var testParams = new { param1 = "value1", param2 = 42 };
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var request = new JsonRpcRequest
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{
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JsonRpc = "2.0",
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Method = "test_method",
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Params = testParams,
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Id = 1
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};
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// Act
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await handler.HandleRequestAsync(request, CancellationToken.None);
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// Assert
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await mockHandler.Received(1).HandleAsync(testParams, Arg.Any<CancellationToken>());
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}
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}
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