chore: remove NIO from tests (#903)

* Remove swift-nio dependencies from tests and add pure Swift HttpTestServer

Replaces NIO-based test servers with a new HttpTestServer implemented using Foundation and POSIX sockets, eliminating the need for swift-nio and related packages in test targets. Updates all affected test files to use the new server and refactors test logic for compatibility. This simplifies test dependencies and improves portability.

* refactor: consolidate HTTP test server implementations

Consolidates two duplicate HTTP test server implementations into a single
shared utility that can be used by both OTLP exporter tests and URLSession
instrumentation tests.

Changes:
- Create unified HttpTestServer in Tests/Shared/TestUtils that combines
  functionality from both previous implementations
- Uses POSIX sockets directly, maintaining independence from external
  dependencies (no NIO, Swifter, etc.)
- Supports OTLP test requirements: request recording, protobuf binary
  payloads, header verification
- Supports URLSession test requirements: path-based responses, success/error
  callbacks, configuration options
- Add SharedTestUtils target to Package.swift for shared test utilities
- Update both test targets to depend on SharedTestUtils
- Remove duplicate implementations from ExportersTests and
  InstrumentationTests
- Update test files to import SharedTestUtils and use consistent API

Benefits:
- Eliminates code duplication between test suites
- Provides consistent HTTP mocking functionality
- Makes it easier to maintain and extend test infrastructure
- All OTLP HTTP exporter tests (16) passing successfully

Note: URLSession tests have 4 pre-existing failures in error handling
that are unrelated to this refactoring.

* Handle /error path in HttpTestServer without config

Added logic to HttpTestServer to properly handle requests to paths starting with /error when no config is provided, simulating a network error by closing the connection without a response.

* Remove unused Darwin import from HttpTestServer.swift

The Darwin import was not used in HttpTestServer.swift

* fix: add Linux compatibility to HTTP test server

- Add conditional imports for Glibc/Musl to support Linux builds
- Replace macOS-specific CFSwapInt16BigToHost with portable ntohs for byte order conversion
- Fix shutdown() calls to use platform-specific namespaces (Darwin/Glibc/Musl)
- Fix minor code warnings (unused variable, boolean test)

The HTTP test server now compiles and runs correctly on both macOS and Linux platforms,
maintaining full backward compatibility while enabling cross-platform support.

This change is required for the test suite to pass in Linux CI environments.

* fix: resolve additional Linux type compatibility issues

- Fix SOCK_STREAM type conversion on Linux (cast __socket_type to Int32)
- Fix SHUT_RDWR type conversion on Linux (cast Int to Int32)

These changes ensure proper type compatibility between macOS and Linux socket APIs.

* fix: Add platform-specific handling for socket creation and warnings

- Add conditional compilation for Darwin vs Linux socket() call
- macOS uses SOCK_STREAM directly, Linux needs Int32(SOCK_STREAM.rawValue)
- Silence unused result warnings for fcntl and withCString calls
- Maintain full compatibility with both OTLP and URLSession tests

* fix: Clear received requests when stopping HttpTestServer

- Ensures clean state when restarting server
- Prevents potential memory leaks from accumulated requests
- Maintains consistency with initialization state

---------

Co-authored-by: Bryce Buchanan <[email protected]>

Author: martin308

Package.swift

@@ -37,6 +37,11 @@ let package = Package(
     .package(url: "https://github.com/apple/swift-metrics.git", from: "2.7.0")
   ],
   targets: [
+    .target(
+      name: "SharedTestUtils",
+      dependencies: [],
+      path: "Tests/Shared/TestUtils"
+    ),
     .target(
       name: "OTelSwiftLog",
       dependencies: [
@@ -147,9 +152,7 @@ let package = Package(
       dependencies: [
         "OpenTelemetryProtocolExporterGrpc",
         "OpenTelemetryProtocolExporterHttp",
-        .product(name: "NIO", package: "swift-nio"),
-        .product(name: "NIOHTTP1", package: "swift-nio"),
-        .product(name: "NIOTestUtils", package: "swift-nio")
+        "SharedTestUtils",
       ],
       path: "Tests/ExportersTests/OpenTelemetryProtocol"
     ),
@@ -308,8 +311,7 @@ extension Package {
           name: "URLSessionInstrumentationTests",
           dependencies: [
             "URLSessionInstrumentation",
-            .product(name: "NIO", package: "swift-nio"),
-            .product(name: "NIOHTTP1", package: "swift-nio")
+            "SharedTestUtils",
           ],
           path: "Tests/InstrumentationTests/URLSessionTests"
         ),

Tests/ExportersTests/OpenTelemetryProtocol/OtlpHTTPExporterBaseTests.swift

@@ -9,9 +9,6 @@
     import FoundationNetworking
   #endif
   import Logging
-  import NIO
-  import NIOHTTP1
-  import NIOTestUtils
   import OpenTelemetryApi
   import OpenTelemetryProtocolExporterCommon
   @testable import OpenTelemetryProtocolExporterHttp

Tests/ExportersTests/OpenTelemetryProtocol/OtlpHTTPMetricsExporterTest.swift

@@ -5,27 +5,23 @@
 
 import Foundation
 import Logging
-import NIO
-import NIOHTTP1
-import NIOTestUtils
 import OpenTelemetryApi
 import OpenTelemetryProtocolExporterCommon
 @testable import OpenTelemetryProtocolExporterHttp
 @testable import OpenTelemetrySdk
 import XCTest
+import SharedTestUtils
 
 class OtlpHttpMetricsExporterTest: XCTestCase {
-  var testServer: NIOHTTP1TestServer!
-  var group: MultiThreadedEventLoopGroup!
+  var testServer: HttpTestServer!
 
   override func setUp() {
-    group = MultiThreadedEventLoopGroup(numberOfThreads: 1)
-    testServer = NIOHTTP1TestServer(group: group)
+    testServer = HttpTestServer()
+    XCTAssertNoThrow(try testServer.start())
   }
 
   override func tearDown() {
     XCTAssertNoThrow(try testServer.stop())
-    XCTAssertNoThrow(try group.syncShutdownGracefully())
   }
 
   // The shutdown() function is a no-op, This test is just here to make codecov happy
@@ -51,7 +47,9 @@ class OtlpHttpMetricsExporterTest: XCTestCase {
       XCTAssertEqual("headerValue", head.headers.first(name: "headerName"))
     })
 
-    XCTAssertNotNil(try testServer.receiveBodyAndVerify())
+    XCTAssertNoThrow(try testServer.receiveBodyAndVerify { _ in 
+      // Body verified
+    })
     XCTAssertNoThrow(try testServer.receiveEnd())
   }
 
@@ -80,10 +78,9 @@ class OtlpHttpMetricsExporterTest: XCTestCase {
     })
 
     XCTAssertNoThrow(try testServer.receiveBodyAndVerify { body in
-      var contentsBuffer = ByteBuffer(buffer: body)
-      let contents = contentsBuffer.readString(length: contentsBuffer.readableBytes)!
+      let bodyString = String(decoding: body, as: UTF8.self)
       for metricDescription in metricDescriptions {
-        XCTAssertTrue(contents.contains(metricDescription))
+        XCTAssertTrue(bodyString.contains(metricDescription))
       }
     })
 
@@ -115,10 +112,9 @@ class OtlpHttpMetricsExporterTest: XCTestCase {
     })
 
     XCTAssertNoThrow(try testServer.receiveBodyAndVerify { body in
-      var contentsBuffer = ByteBuffer(buffer: body)
-      let contents = contentsBuffer.readString(length: contentsBuffer.readableBytes)!
+      let bodyString = String(decoding: body, as: UTF8.self)
       for metricDescription in metricDescriptions {
-        XCTAssertTrue(contents.contains(metricDescription))
+        XCTAssertTrue(bodyString.contains(metricDescription))
       }
     })
 

Tests/ExportersTests/OpenTelemetryProtocol/OtlpHttpLogRecordExporterTests.swift

@@ -5,23 +5,20 @@
 
 import Foundation
 import Logging
-import NIO
-import NIOHTTP1
-import NIOTestUtils
 import OpenTelemetryApi
 import OpenTelemetryProtocolExporterCommon
 @testable import OpenTelemetryProtocolExporterHttp
 @testable import OpenTelemetrySdk
 import XCTest
+import SharedTestUtils
 
 class OtlpHttpLogRecordExporterTests: XCTestCase {
-  var testServer: NIOHTTP1TestServer!
-  var group: MultiThreadedEventLoopGroup!
+  var testServer: HttpTestServer!
   var spanContext: SpanContext!
 
   override func setUp() {
-    group = MultiThreadedEventLoopGroup(numberOfThreads: 1)
-    testServer = NIOHTTP1TestServer(group: group)
+    testServer = HttpTestServer()
+    XCTAssertNoThrow(try testServer.start())
 
     let spanId = SpanId.random()
     let traceId = TraceId.random()
@@ -30,7 +27,6 @@ class OtlpHttpLogRecordExporterTests: XCTestCase {
 
   override func tearDown() {
     XCTAssertNoThrow(try testServer.stop())
-    XCTAssertNoThrow(try group.syncShutdownGracefully())
   }
 
   func testExport() {
@@ -60,9 +56,8 @@ class OtlpHttpLogRecordExporterTests: XCTestCase {
       XCTAssertEqual(otelVersion, head.headers.first(name: Constants.HTTP.userAgent))
     })
     XCTAssertNoThrow(try testServer.receiveBodyAndVerify { body in
-      var contentsBuffer = ByteBuffer(buffer: body)
-      let contents = contentsBuffer.readString(length: contentsBuffer.readableBytes)!
-      XCTAssertTrue(contents.description.contains(testBody.description))
+      let bodyString = String(decoding: body, as: UTF8.self)
+      XCTAssertTrue(bodyString.contains(testBody.description))
     })
 
     XCTAssertNoThrow(try testServer.receiveEnd())

Tests/ExportersTests/OpenTelemetryProtocol/OtlpHttpTraceExporterTests.swift

@@ -8,27 +8,23 @@ import Foundation
   import FoundationNetworking
 #endif
 import Logging
-import NIO
-import NIOHTTP1
-import NIOTestUtils
 import OpenTelemetryApi
 import OpenTelemetryProtocolExporterCommon
 @testable import OpenTelemetryProtocolExporterHttp
 @testable import OpenTelemetrySdk
 import XCTest
+import SharedTestUtils
 
 class OtlpHttpTraceExporterTests: XCTestCase {
-  var testServer: NIOHTTP1TestServer!
-  var group: MultiThreadedEventLoopGroup!
+  var testServer: HttpTestServer!
 
   override func setUp() {
-    group = MultiThreadedEventLoopGroup(numberOfThreads: 1)
-    testServer = NIOHTTP1TestServer(group: group)
+    testServer = HttpTestServer()
+    XCTAssertNoThrow(try testServer.start())
   }
 
   override func tearDown() {
     XCTAssertNoThrow(try testServer.stop())
-    XCTAssertNoThrow(try group.syncShutdownGracefully())
   }
 
   // This is a somewhat hacky solution to verifying that the spans got across correctly.  It simply looks for the metric
@@ -56,10 +52,11 @@ class OtlpHttpTraceExporterTests: XCTestCase {
       XCTAssertEqual(otelVersion, head.headers.first(name: Constants.HTTP.userAgent))
     })
     XCTAssertNoThrow(try testServer.receiveBodyAndVerify { body in
-      var contentsBuffer = ByteBuffer(buffer: body)
-      let contents = contentsBuffer.readString(length: contentsBuffer.readableBytes)!
-      XCTAssertTrue(contents.contains(endpointName1))
-      XCTAssertTrue(contents.contains(endpointName2))
+      XCTAssertTrue(body.count > 0, "Body should not be empty")
+      // Check that endpoint names are present in the protobuf data
+      let bodyString = String(decoding: body, as: UTF8.self)
+      XCTAssertTrue(bodyString.contains(endpointName1))
+      XCTAssertTrue(bodyString.contains(endpointName2))
     })
 
     XCTAssertNoThrow(try testServer.receiveEnd())
@@ -68,6 +65,9 @@ class OtlpHttpTraceExporterTests: XCTestCase {
   // This is not a thorough test of HTTPClient, but just enough to keep code coverage happy.
   // There is a more complete test as part of the DataDog exporter test
   func testHttpClient() {
+    // Clear any previous requests
+    testServer.clearReceivedRequests()
+    
     let endpoint = URL(string: "http://localhost:\(testServer.serverPort)/some-route")!
     let httpClient = BaseHTTPClient()
     var request = URLRequest(url: endpoint)
@@ -76,7 +76,7 @@ class OtlpHttpTraceExporterTests: XCTestCase {
     httpClient.send(request: request) { result in
       switch result {
       case let .success(response):
-        XCTAssertEqual(HTTPResponseStatus.imATeapot.code, UInt(response.statusCode))
+        XCTAssertEqual(HTTPResponseStatus.ok.code, UInt(response.statusCode))
       case let .failure(error):
         XCTFail("Send failed: \(error)")
       }
@@ -85,16 +85,10 @@ class OtlpHttpTraceExporterTests: XCTestCase {
     // Assert the server received the expected request.
     XCTAssertNoThrow(try testServer.receiveHeadAndVerify { head in
       XCTAssertEqual(head.version, .http1_1)
-      XCTAssertEqual(head.method, .GET)
+      XCTAssertEqual(head.method.rawValue, "GET")
       XCTAssertEqual(head.uri, "/some-route")
     })
-    XCTAssertNoThrow(try testServer.receiveEndAndVerify { trailers in
-      XCTAssertNil(trailers)
-    })
-
-    // Make the server send a response to the client.
-    XCTAssertNoThrow(try testServer.writeOutbound(.head(.init(version: .http1_1, status: .imATeapot))))
-    XCTAssertNoThrow(try testServer.writeOutbound(.end(nil)))
+    XCTAssertNoThrow(try testServer.receiveEnd())
   }
 
   func testFlush() {

Tests/InstrumentationTests/URLSessionTests/URLSessionInstrumentationTests.swift

@@ -7,6 +7,7 @@
 @testable import OpenTelemetrySdk
 @testable import URLSessionInstrumentation
 import XCTest
+import SharedTestUtils
 
 class URLSessionInstrumentationTests: XCTestCase {
   class Check {