Implemented the User Agent middleware (#6)

This PR contains the work done to implement the `UserAgentMiddleware` middleware that includes user agent information into a header of the requests sent by the `Client` type, as defined in the [Discogs documentation](https://www.discogs.com/developers/#page:home,header:home-general-information). For this purpose, the `CamelCaseValidationRule`, `SemanticVersionValidationRule` and `URLValidationRule` types were implemented and integrated into the existing `ValidateInputUseCase` type.

Reviewed-on: #6
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Co-committed-by: Javier Cicchelli <javier@rock-n-code.com>

Tests/DiscogsService/Cases/Internal/Extensions/String+FunctionsTests.swift

@@ -0,0 +1,99 @@
+// ===----------------------------------------------------------------------===
+//
+// This source file is part of the DiscogsService open source project
+//
+// Copyright (c) 2025 Röck+Cöde VoF. and the DiscogsService project authors
+// Licensed under Apache license v2.0
+//
+// See LICENSE for license information
+// See CONTRIBUTORS for the list of DiscogsService project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+// ===----------------------------------------------------------------------===
+
+import Testing
+
+@testable import DiscogsService
+
+@Suite("String Functions", .tags(.extension))
+struct StringFunctionsTests {
+    
+    // MARK: Functions tests
+    
+#if swift(>=6.2)
+    @Test(arguments: zip(
+        Input.stringsToMatch,
+        Output.stringsToMatch
+    ))
+    func `fully match`(
+        string: String,
+        expects isMatch: Bool
+    ) {
+        assertFullyMatch(
+            string: string,
+            pattern: .Pattern.sample,
+            expects: isMatch
+        )
+    }
+#else
+    @Test("fully match", arguments: zip(
+        Input.stringsToMatch,
+        Output.stringsToMatch
+    ))
+    func fullyMatch(
+        string: String,
+        expects isMatch: Bool
+    ) {
+        assertFullyMatch(
+            string: string,
+            pattern: .Pattern.sample,
+            expects: isMatch
+        )
+    }
+#endif
+    
+}
+
+// MARK: - Assertions
+
+private extension StringFunctionsTests {
+    
+    // MARK: Functions
+    
+    /// Asserts the result of the `fullyMatch` function.
+    /// - Parameters:
+    ///   - string: A string to match against a pattern.
+    ///   - pattern: A regular expression pattern to match a string against.
+    ///   - isMatch: An expected flag that indicates whether there is a match or not.
+    func assertFullyMatch(
+        string: String,
+        pattern: String,
+        expects isMatch: Bool
+    ) {
+        // GIVEN
+        // WHEN
+        let result = string.fullyMatch(pattern: pattern)
+
+        // THEN
+        #expect(result == isMatch)
+    }
+    
+}
+
+// MARK: - Constants
+
+private extension Input {
+    /// A list of strings to match against a regular expression pattern in test cases.
+    static let stringsToMatch: [String] = ["Some Pattern", "Some", "Some Other Pattern", "Pattern", .empty]
+}
+
+private extension Output {
+    /// A list of expected results from matching a sample string against a sample regular expression pattern in test cases.
+    static let stringsToMatch: [Bool] = [true, false, false, false, false]
+}
+
+private extension String.Pattern {
+    /// A sample regular expression pattern to match against.
+    static let sample = "Some Pattern"
+}

Tests/DiscogsService/Cases/Internal/Use Cases/ValidateInputUseCaseTests.swift

@@ -22,6 +22,20 @@ struct ValidateInputUseCaseTests {
     // MARK: Functions
     
 #if swift(>=6.2)
+    @Test(arguments: zip(
+        Input.inputsAgentName,
+        Output.inputsAgentName
+    )) func `validate camel case`(
+        input: String,
+        expects error: InputValidationError?
+    ) async throws {
+        try assertValidate(
+            rule: .agentName,
+            input: input,
+            expects: error
+        )
+    }
+
     @Test(arguments: zip(
         Input.inputsNotEmpty,
         Output.inputsNotEmpty
@@ -91,7 +105,49 @@ struct ValidateInputUseCaseTests {
             expects: error
         )
     }
+    
+    @Test(arguments: zip(
+        Input.inputsSemanticVersion,
+        Output.inputsSemanticVersion
+    )) func `validate semantic version`(
+        input: String?,
+        expects error: InputValidationError?
+    ) async throws {
+        try assertValidate(
+            rule: .semanticVersion,
+            input: input,
+            expects: error
+        )
+    }
+    
+    @Test(arguments: zip(
+        Input.inputsURL,
+        Output.inputsURL
+    )) func `validate url`(
+        input: String?,
+        expects error: InputValidationError?
+    ) async throws {
+        try assertValidate(
+            rule: .url,
+            input: input,
+            expects: error
+        )
+    }
 #else
+    @Test("validate camel case", arguments: zip(
+        Input.inputsCamelCase,
+        Output.inputsCamelCase
+    )) func validateCamelCase(
+        input: String,
+        expects error: InputValidationError?
+    ) async throws {
+        try assertValidate(
+            rule: .camelCase,
+            input: input,
+            expects: error
+        )
+    }
+
     @Test("validate not empty", arguments: zip(
         Input.inputsNotEmpty,
         Output.inputsNotEmpty
@@ -161,6 +217,34 @@ struct ValidateInputUseCaseTests {
             expects: error
         )
     }
+    
+    @Test("validate semantic version", arguments: zip(
+        Input.inputsSemanticVersion,
+        Output.inputsSemanticVersion
+    )) func validateSemanticVersion(
+        input: String?,
+        expects error: InputValidationError?
+    ) async throws {
+        try assertValidate(
+            rule: .semanticVersion,
+            input: input,
+            expects: error
+        )
+    }
+    
+    @Test("validate url", arguments: zip(
+        Input.inputsURL,
+        Output.inputsURL
+    )) func validateURL(
+        input: String?,
+        expects error: InputValidationError?
+    ) async throws {
+        try assertValidate(
+            rule: .url,
+            input: input,
+            expects: error
+        )
+    }
 #endif
     
 }
@@ -203,6 +287,8 @@ private extension ValidateInputUseCaseTests {
 // MARK: - Constants
 
 private extension Input {
+    /// A list of inputs to validate against a camel-case validation rule.
+    static let inputsCamelCase: [String] = ["SampleApp", "Sample4pp", "SampleApp1", "SampleApp🚀", "Sample App", "Sample-App", "Sample_App"]
     /// A list of inputs to validate against the not empty validation rule.
     static let inputsNotEmpty: [String] = ["Something", .empty]
     /// A list of inputs to validate against the not nil validation rule.
@@ -213,9 +299,15 @@ private extension Input {
     static let inputsSecureConsumerSecret: [String] = ["aAbBcCdDeEfFgGhHiIjJkKlLmMnNoOpP", "aAbBcCdDeEfFgGhHiIjJkKlLmMnNoO", "aAbBcCdDeEfFgGhHiIjJkKlLmMnNoOpPqQ", "a4bBcCdDe3fFg6hH1IjJkK1LmMnNo0p9"]
     /// A list of inputs to validate against the secure (user token) validation rule.
     static let inputsSecureUserToken: [String] = ["aAbBcCdDeEfFgGhHiIjJkKlLmMnNoOpPqQrRsStT", "aAbBcCdDeEfFgGhHiIjJkKlLmMnNoOpPqQrRsS", "aAbBcCdDeEfFgGhHiIjJkKlLmMnNoOpPqQrRsStTuU", "a4bBcCdDe3fFg6hH1IjJkK1LmMnNo0p9qQrRs5t7"]
+    /// A list of inputs to validate against the semantic version validation rule.
+    static let inputsSemanticVersion: [String] = ["0.0.4","1.2.3","10.20.30","1.1.2-prerelease+meta","1.1.2+meta","1.1.2+meta-valid","1.0.0-alpha","1.0.0-beta","1.0.0-alpha.beta","1.0.0-alpha.beta.1","1.0.0-alpha.1","1.0.0-alpha0.valid","1.0.0-alpha.0valid","1.0.0-alpha-a.b-c-somethinglong+build.1-aef.1-its-okay","1.0.0-rc.1+build.1","2.0.0-rc.1+build.123","1.2.3-beta","10.2.3-DEV-SNAPSHOT","1.2.3-SNAPSHOT-123","1.0.0","2.0.0","1.1.7","2.0.0+build.1848","2.0.1-alpha.1227","1.0.0-alpha+beta","1.2.3----RC-SNAPSHOT.12.9.1--.12+788","1.2.3----R-S.12.9.1--.12+meta","1.2.3----RC-SNAPSHOT.12.9.1--.12","1.0.0+0.build.1-rc.10000aaa-kk-0.1","99999999999999999999999.999999999999999999.99999999999999999","1.0.0-0A.is.legal","1","1.2","1.2.3-0123","1.2.3-0123.0123","1.1.2+.123","+invalid","-invalid","-invalid+invalid","-invalid.01","alpha","alpha.beta","alpha.beta.1","alpha.1","alpha+beta","alpha_beta","alpha.","alpha..","beta","1.0.0-alpha_beta","-alpha.","1.0.0-alpha..","1.0.0-alpha..1","1.0.0-alpha...1","1.0.0-alpha....1","1.0.0-alpha.....1","1.0.0-alpha......1","1.0.0-alpha.......1","01.1.1","1.01.1","1.1.01","1.2","1.2.3.DEV","1.2-SNAPSHOT","1.2.31.2.3----RC-SNAPSHOT.12.09.1--..12+788","1.2-RC-SNAPSHOT","-1.0.3-gamma+b7718","+justmeta","9.8.7+meta+meta","9.8.7-whatever+meta+meta","99999999999999999999999.999999999999999999.99999999999999999----RC-SNAPSHOT.12.09.1--------------------------------..12"]
+    /// A list of inputs to validate against the URL validation rule.
+    static let inputsURL: [String] = ["https://www.google.com", "http://www.google.com", "https://google.com/q=search", "http://google.com/q=search", "3333-768-0948", "1133.168.0248", "7678*999-8978", "httpq://google.com/q=search", "www.google.com", "www.google.com/?search=qppoao", "www . google.com/?search=qppoao", "https : //google.com/q=search", "htt://www.google.com", "://www.google.com", .empty]
 }
 
 private extension Output {
+    /// A list of expected input validation errors to be thrown after validating inputs against the camel-case validation rule.
+    static let inputsCamelCase: [InputValidationError?] = [nil, nil, nil, .inputNotCamelCase, .inputNotCamelCase, .inputNotCamelCase, .inputNotCamelCase]
     /// A list of expected input validation errors to be thrown after validating inputs against the not empty validation rule.
     static let inputsNotEmpty: [InputValidationError?] = [nil, .inputIsEmpty]
     /// A list of expected input validation errors to be thrown after validating inputs against the not nil validation rule.
@@ -226,4 +318,8 @@ private extension Output {
     static let inputsSecureConsumerSecret: [InputValidationError?] = [nil, .inputNotConsumerSecret, .inputNotConsumerSecret, .inputNotConsumerSecret]
     /// A list of expected input validation errors to be thrown after validating inputs against the secure (user token) validation rule.
     static let inputsSecureUserToken: [InputValidationError?] = [nil, .inputNotUserToken, .inputNotUserToken, .inputNotUserToken]
+    /// A list of expected input validation errors to be thrown after validating inputs against the semantic version validation rule.
+    static let inputsSemanticVersion: [InputValidationError?] = [nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputNotSemanticVersion]
+    /// A list of expected input validation errors to be thrown after validating inputs against the URL validation rule.
+    static let inputsURL: [InputValidationError?] = [nil, nil, nil, nil, .inputNotURL, .inputNotURL, .inputNotURL, .inputNotURL, .inputNotURL, .inputNotURL, .inputNotURL, .inputNotURL, .inputNotURL, .inputNotURL, .inputNotURL]
 }

Tests/DiscogsService/Cases/Public/Middlewares/AuthMiddlewareTests.swift

@@ -15,7 +15,6 @@
 import struct Foundation.URL
 import struct Foundation.URLComponents
 import struct Foundation.URLQueryItem
-import struct HTTPTypes.HTTPField
 import struct HTTPTypes.HTTPFields
 import struct HTTPTypes.HTTPRequest
 import struct HTTPTypes.HTTPResponse
@@ -28,6 +27,7 @@ import Testing
 struct AuthMiddlewareTests {
     
     // MARK: Initializers tests
+
 #if swift(>=6.2)
     @Test(arguments: Input.authMethods)
     func `initialize`(
@@ -273,11 +273,11 @@ private extension AuthMiddlewareTests {
         }
     }
 
-    /// Asserts the error throwing (if justified) during the initialization of the middleware.
+    /// Asserts the error throwing (if justified) during the initialization of a middleware.
     /// - Parameters:
     ///   - authMethod: A representation of an authentication method.
     ///   - authTransport: A representation of an authentication transport.
-    ///   - error: An expected error of type ``InputValidationError`` during the initialization of the middleware.
+    ///   - error: An expected error of type ``InputValidationError`` during the initialization of a middleware.
     func assertInitThrows(
         authMethod: AuthMethod,
         authTransport: AuthTransport,
@@ -331,8 +331,8 @@ private extension AuthMiddlewareTests {
             try await middleware.intercept(
                 request,
                 body: nil,
-                baseURL: .baseURL,
-                operationID: .operationId
+                baseURL: .Sample.baseURL,
+                operationID: .Sample.operationId
             ) { request, _, _ in
                 // THEN
                 switch (authMethod, authTransport) {
@@ -430,31 +430,6 @@ private extension AuthMiddlewareTests {
     
 }
 
-private extension HTTPRequest {
-    
-    // MARK: Initializers
-    
-    /// Initializes a HTTP request conveniently.
-    /// - Parameters:
-    ///   - method: A request method.
-    ///   - path: A value of the “:path” pseudo header field.
-    ///   - headerFields: A dictionary of request header fields.
-    init(
-        method: HTTPRequest.Method = .get,
-        path: String?,
-        headerFields: HTTPFields = [:]
-    ) {
-        self.init(
-            method: method,
-            scheme: nil,
-            authority: nil,
-            path: path,
-            headerFields: headerFields
-        )
-    }
-    
-}
-
 // MARK: - Constants
 
 private extension Input {
@@ -464,7 +439,7 @@ private extension Input {
         .user(token: "aAbBcCdDeEfFgGhHiIjJkKlLmMnNoOpPqQrRsStT"),
         .none
     ]
-    /// A list of authentication methods to tests for the initialization throw test cases.
+    /// A list of authentication methods to use in the initialization throw test cases.
     static let authMethodsThrows: [AuthMethod] = authMethods + [
         .consumer(key: .empty, secret: "aAbBcCdDeEfFgGhHiIjJkKlLmMnNoOpP"),
         .consumer(key: "aAbBcCdDeEfFgGhHiI", secret: "aAbBcCdDeEfFgGhHiIjJkKlLmMnNoOpP"),
@@ -487,13 +462,3 @@ private extension Output {
     /// A list of expected boolean flags coming from the should authenticate test cases.
     static let authMethodsShouldAuthenticate: [Bool] = [true, true, false]
 }
-
-private extension String {
-    /// An operation ID sample.
-    static let operationId = "SomeOperationId"
-}
-
-private extension URL {
-    /// A base URL sample.
-    static let baseURL = URL(string: "https://sample.domain.com")!
-}

Tests/DiscogsService/Cases/Public/Middlewares/UserAgentMiddlewareTests.swift

@@ -12,14 +12,215 @@
 //
 // ===----------------------------------------------------------------------===
 
-import DiscogsService
+import struct HTTPTypes.HTTPField
+import struct HTTPTypes.HTTPFields
+import struct HTTPTypes.HTTPRequest
+
 import Testing
 
+@testable import DiscogsService
+
 @Suite("User Agent Middleware", .tags(.middleware))
 struct UserAgentMiddlewareTests {
-
-//    @Test func <#test function name#>() async throws {
-//        // Write your test here and use APIs like `#expect(...)` to check expected conditions.
-//    }
-
+    
+    // MARK: Initializers tests
+    
+#if swift(>=6.2)
+    @Test(arguments: Input.userAgents)
+    func `initialize`(
+        product: Product
+    ) throws {
+        try assertInit(product: product)
+    }
+    
+    @Test(arguments: zip(
+        Input.userAgentsThrows,
+        Output.userAgentsThrows
+    ))
+    func `initialize throws`(
+        product: Product,
+        expect error: InputValidationError?
+    ) {
+        assertInitThrows(
+            product: product,
+            expects: error
+        )
+    }
+#else
+    @Test("initialize", arguments: Input.userAgents)
+    func initialize(
+        product: Product
+    ) throws {
+        try assertInit(product: product)
+    }
+    
+    @Test("initialize throws", arguments: zip(
+        Input.userAgentsThrows,
+        Output.userAgentsThrows
+    ))
+    func initializeThrows(
+        product: Product,
+        expect error: InputValidationError?
+    ) {
+        assertInitThrows(
+            product: product,
+            expects: error
+        )
+    }
+#endif
+    
+    // MARK: Functions tests
+    
+#if swift(>=6.2)
+    @Test(arguments: Input.userAgents)
+    func `intercept with user agent on headers`(
+        product: Product
+    ) async throws {
+        try await assertIntercept(product: product)
+    }
+    
+    @Test(arguments: Input.userAgents)
+    func `intercept with user agent on headers when headers are populated`(
+        product: Product
+    ) async throws {
+        try await assertIntercept(
+            product: product,
+            headerFields: [.accept: "*/*"]
+        )
+    }
+#else
+    @Test("intercept with user agent on headers", arguments: Input.userAgents)
+    func intercept_withUserAgentOnHeaders(
+        product: Product
+    ) async throws {
+        try await assertIntercept(product: product)
+    }
+    
+    @Test("intercept with user agent on headers when headers are populated", arguments: Input.userAgents)
+    func intercept_withUserAgentOnHeaders_whenHeadersPopulated(
+        product: Product
+    ) async throws {
+        try await assertIntercept(
+            product: product,
+            headerFields: [.accept: "*/*"]
+        )
+    }
+#endif
+    
+}
+
+// MARK: - Assertions
+
+private extension UserAgentMiddlewareTests {
+    
+    // MARK: Functions
+    
+    /// Asserts the initialization of the middleware , especially the assignments of its properties.
+    /// - Parameter product: A product to initialize a middleware.
+    /// - Throws: an error of type ``InputValidationError`` in case of an unexpected error occurs while running test cases.
+    func assertInit(
+        product: Product
+    ) throws {
+        // GIVEN
+        // WHEN
+        let middleware = try UserAgentMiddleware(product: product)
+        
+        // THEN
+        #expect(middleware.agentField == .init(
+            name: .userAgent,
+            value: "\(product.name)/\(product.version) +\(product.url)"
+        ))
+    }
+    
+    /// Asserts the error throwing (if justified) during the initialization of the middleware.
+    /// - Parameters:
+    ///   - product: A product to initialize a middleware.
+    ///   - error: An expected error of type ``InputValidationError`` during the initialization of a middleware.
+    func assertInitThrows(
+        product: Product,
+        expects error: InputValidationError?
+    ) {
+        // GIVEN
+        // WHEN
+        // THEN
+        if let error {
+            #expect(throws: error) {
+                try UserAgentMiddleware(product: product)
+            }
+        } else {
+            #expect(throws: Never.self) {
+                try UserAgentMiddleware(product: product)
+            }
+        }
+    }
+    
+    /// Asserts the interception of a request to add the user agent in its header.
+    /// - Parameters:
+    ///   - product: A product to initialize a middleware.
+    ///   - path: A URI path for a request.
+    ///   - headerFields: A set of header fields for a request.
+    func assertIntercept(
+        product: Product,
+        path: String? = nil,
+        headerFields: HTTPFields = [:]
+    ) async throws {
+        // GIVEN
+        let middleware = try UserAgentMiddleware(product: product)
+        let request = HTTPRequest(
+            path: path,
+            headerFields: headerFields
+        )
+
+        // WHEN
+        _ = try await confirmation { confirmation in
+            try await middleware.intercept(
+                request,
+                body: nil,
+                baseURL: .Sample.baseURL,
+                operationID: .Sample.operationId
+            ) { request, _, _ in
+                // THEN
+                #expect(request.path == path)
+                #expect(request.headerFields != headerFields)
+                #expect(request.headerFields.count == headerFields.count + 1)
+                #expect(request.headerFields.contains(where: { $0.name == .userAgent }))
+                
+                confirmation()
+                
+                return (.init(status: .ok) , nil)
+            }
+        }
+    }
+    
+}
+
+// MARK: - Constants
+
+private extension Input {
+    /// A list of products to successfully initialize user agent middleware instances.
+    static let userAgents: [Product] = [
+        .init(name: "SomeApp", version: "0.0.1", url: "http://www.some.app"),
+        .init(name: "SomeOther4pp", version: "1.2.3-b1", url: "https://some-other.app"),
+        .init(name: "Yet4notherApp", version: "0.8.8+alpha", url: "https://yet.another.app")
+    ]
+    /// A list of products to use in the initialization throw test cases.
+    static let userAgentsThrows: [Product] = userAgents + [
+        .init(name: "Some App", version: "0.0.1", url: "http://www.some.app"),
+        .init(name: "Some-App", version: "0.0.1", url: "http://www.some.app"),
+        .init(name: .empty, version: "0.0.1", url: "http://www.some.app"),
+        .init(name: "SomeApp", version: "v0.0.1", url: "http://www.some.app"),
+        .init(name: "SomeApp", version: "0.1", url: "http://www.some.app"),
+        .init(name: "SomeApp", version: .empty, url: "http://www.some.app"),
+        .init(name: "SomeApp", version: "0.0.1", url: "www.some.app"),
+        .init(name: "SomeApp", version: "0.0.1", url: "some.app"),
+        .init(name: "SomeApp", version: "0.0.1", url: .empty),
+        .init(name: "Some App", version: "v0.0.1", url: "www.some.app"),
+        .init(name: "SomeApp", version: "v0.0.1", url: "www.some.app"),
+        .init(name: "Some App", version: "0.0.1", url: "www.some.app"),
+    ]
+}
+
+private extension Output {
+    /// A list of expected input validation errors (if thrown) coming from the initialization throw test cases.
+    static let userAgentsThrows: [InputValidationError?] = [nil, nil, nil, .inputNotCamelCase, .inputNotCamelCase, .inputIsEmpty, .inputNotSemanticVersion, .inputNotSemanticVersion, .inputIsEmpty, .inputNotURL, .inputNotURL, .inputIsEmpty, .inputNotCamelCase,  .inputNotSemanticVersion, .inputNotCamelCase]
 }

Tests/DiscogsService/Types/Extensions/HTTPRequests+Inits.swift

@@ -0,0 +1,41 @@
+// ===----------------------------------------------------------------------===
+//
+// This source file is part of the DiscogsService open source project
+//
+// Copyright (c) 2025 Röck+Cöde VoF. and the DiscogsService project authors
+// Licensed under Apache license v2.0
+//
+// See LICENSE for license information
+// See CONTRIBUTORS for the list of DiscogsService project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+// ===----------------------------------------------------------------------===
+
+import struct HTTPTypes.HTTPFields
+import struct HTTPTypes.HTTPRequest
+
+extension HTTPRequest {
+    
+    // MARK: Initializers
+    
+    /// Initializes a HTTP request conveniently.
+    /// - Parameters:
+    ///   - method: A request method.
+    ///   - path: A value of the “:path” pseudo header field.
+    ///   - headerFields: A dictionary of request header fields.
+    init(
+        method: HTTPRequest.Method = .get,
+        path: String?,
+        headerFields: HTTPFields = [:]
+    ) {
+        self.init(
+            method: method,
+            scheme: nil,
+            authority: nil,
+            path: path,
+            headerFields: headerFields
+        )
+    }
+    
+}

Tests/DiscogsService/Types/Extensions/Tag+Customs.swift

@@ -18,6 +18,9 @@ extension Tag {
     
     // MARK: Constants
     
+    /// A tag that indicates tests for a type extension.
+    @Tag static var `extension`: Self
+    
     /// A tag that indicates tests for a middleware type.
     @Tag static var middleware: Self
     

Tests/DiscogsService/Types/Samples/String+Samples.swift

@@ -0,0 +1,21 @@
+// ===----------------------------------------------------------------------===
+//
+// This source file is part of the DiscogsService open source project
+//
+// Copyright (c) 2025 Röck+Cöde VoF. and the DiscogsService project authors
+// Licensed under Apache license v2.0
+//
+// See LICENSE for license information
+// See CONTRIBUTORS for the list of DiscogsService project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+// ===----------------------------------------------------------------------===
+
+extension String {
+    /// A namespace assigned for string samples on test cases.
+    enum Sample {
+        /// An operation ID sample.
+        static let operationId = "SomeOperationId"
+    }
+}

Tests/DiscogsService/Types/Samples/URL+Samples.swift

@@ -0,0 +1,23 @@
+// ===----------------------------------------------------------------------===
+//
+// This source file is part of the DiscogsService open source project
+//
+// Copyright (c) 2025 Röck+Cöde VoF. and the DiscogsService project authors
+// Licensed under Apache license v2.0
+//
+// See LICENSE for license information
+// See CONTRIBUTORS for the list of DiscogsService project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+// ===----------------------------------------------------------------------===
+
+import Foundation
+
+extension URL {
+    /// A namespace assigned for URL samples on test cases.
+    enum Sample {
+        /// A base URL sample.
+        static let baseURL = URL(string: "https://sample.domain.com")!
+    }
+}