Feature: Support for multiple instances of HTTPMock

.github/workflows/unit-tests.yml

@@ -21,4 +21,4 @@ jobs:
         run: swift build
 
       - name: Test
-        run: swift test --no-parallel
+        run: swift test --parallel

HTTPMock.xctestplan

@@ -13,7 +13,6 @@
   },
   "testTargets" : [
     {
-      "parallelizable" : false,
       "target" : {
         "containerPath" : "container:",
         "identifier" : "HTTPMockTests",

README.md

@@ -23,8 +23,8 @@ A tiny, test-first way to mock `URLSession` — **fast to set up, easy to read,
 
 ## Highlights
 - **Two ways to add mocks**: a **clean DSL** or **single registration methods** — use whichever reads best for your use case.
-- **Singleton API**: `HTTPMock.shared` is the only instance you need. No global state leaks between tests: clear with `clearQueues()`.
-- **Works with real `URLSession`**: inject `HTTPMock.shared.urlSession` into the code under test. 
+- **Instance or singleton**: you can either use the singleton `HTTPMock.shared` or create separate instances with `HTTPMock()`. Different instances have separate response queues.
+- **Provides a real `URLSession`**: inject `HTTPMock.shared.urlSession` or your own instance's `urlSession` into the code under test. 
 - **Precise matching**: host + path, plus optional **query matching** (`.exact` or `.contains`).
 - **Headers support**: define headers at the host or path, with optional **cascade** to children when using the DSL.
 - **FIFO responses**: queue multiple responses and they'll be served in order.
@@ -35,7 +35,7 @@ A tiny, test-first way to mock `URLSession` — **fast to set up, easy to read,
 Add this package to your test target:
 
 ```swift
-.package(url: "https://github.com/bstien/HTTPMock.git", from: "0.0.1")
+.package(url: "https://github.com/bstien/HTTPMock.git", from: "0.0.3")
 ```
 
 ## Quick start
@@ -193,12 +193,43 @@ HTTPMock.shared.clearQueues()
 HTTPMock.shared.clearQueue(forHost: "domain.com")
 ```
 
+## Singleton vs. separate instances
+You can use the global singleton `HTTPMock.shared` for simplicity in most cases. However, if you need isolated queues to, for example, run parallel tests or maintain different mock configurations you can create separate instances with `HTTPMock()`.
+
+Each instance maintains their own queue and properties, and they have no connection to each other.
+
+Example:
+
+```swift
+// Using the singleton
+HTTPMock.shared.registerResponses {
+    Host("api.example.com") {
+        Path("/user") {
+            MockResponse.plaintext("Hello from singleton!")
+        }
+    }
+}
+let singletonSession = HTTPMock.shared.urlSession
+
+// Using a separate instance.
+let mockInstance = HTTPMock()
+mockInstance.registerResponses {
+    Host("api.example.com") {
+        Path("/user") {
+            MockResponse.plaintext("Hello from instance!")
+        }
+    }
+}
+let instanceSession = mockInstance.urlSession
+```
+
+
 ## FAQs
 **Can I run tests that use `HTTPMock` in parallel?**  
-No, currently only a single instance of `HTTPMock` can exist, so tests must be run sequentially.
+Previously, only a single instance of `HTTPMock` could exist, so tests had to be run sequentially. Now, you can create multiple independent `HTTPMock` instances using `HTTPMock()`, allowing parallel tests or separate mock configurations. The singleton `HTTPMock.shared` still exists for convenience.
 
 **Can I use my own `URLSession`?**  
-Yes — most tests just use `HTTPMock.shared.urlSession`. If your code constructs its own session, inject `HTTPMock.shared.urlSession` into the component under test.
+Yes — most tests just use `HTTPMock.shared.urlSession`. If your code constructs its own session, inject `HTTPMock.shared.urlSession` or your own instance's `urlSession` into the component under test.
 
 **Is order guaranteed?**  
 Yes, per (host, path, [query]) responses are popped in **FIFO** order.
@@ -237,6 +268,6 @@ Path("/user") {
 - [X] Allow for passthrough networking when mock hasn't been registered for the incoming URL.
 - [X] Let user point to a file that should be served.
 - [X] Set delay on requests.
+- [X] Create separate instances of `HTTPMock`. The current single instance requires tests to be run in sequence, instead of parallel.
 - [ ] Let user configure a default "not found" response. Will be used either when no matching mocks are found or if queue is empty.
-- [ ] Create separate instances of `HTTPMock`. The current single instance requires tests to be run in sequence, instead of parallel.
 - [ ] Does arrays in query parameters work? I think they're being overwritten with the current setup.

Sources/HTTPMock/Extensions/URLSession+Extensions.swift

@@ -0,0 +1,22 @@
+import Foundation
+import ObjectiveC.runtime
+
+private var MockIdentifierKey: UInt8 = 0
+
+extension URLSession {
+    /// Attach/read a UUID on a URLSession instance.
+    var mockIdentifier: UUID? {
+        get { objc_getAssociatedObject(self, &MockIdentifierKey) as? UUID }
+        set { objc_setAssociatedObject(self, &MockIdentifierKey, newValue, .OBJC_ASSOCIATION_RETAIN_NONATOMIC) }
+    }
+
+    static func identifiedSession(with identifier: UUID) -> URLSession {
+        let configuration = URLSessionConfiguration.ephemeral
+        configuration.protocolClasses = [HTTPMockURLProtocol.self]
+
+        let urlSession = URLSession(configuration: configuration)
+        urlSession.mockIdentifier = identifier
+
+        return urlSession
+    }
+}

Sources/HTTPMock/HTTPMock+ResultBuilder.swift

@@ -17,7 +17,7 @@ extension HTTPMock {
                     queryItems: registration.queryItems,
                     queryMatching: registration.queryMatching ?? .exact
                 )
-                HTTPMockURLProtocol.add(responses: finalResponses, forKey: key)
+                HTTPMockURLProtocol.add(responses: finalResponses, forKey: key, forMockIdentifier: mockIdentifier)
             }
         }
     }
@@ -38,7 +38,7 @@ extension HTTPMock {
                 queryItems: registration.queryItems,
                 queryMatching: registration.queryMatching ?? .exact
             )
-            HTTPMockURLProtocol.add(responses: finalResponses, forKey: key)
+            HTTPMockURLProtocol.add(responses: finalResponses, forKey: key, forMockIdentifier: mockIdentifier)
         }
     }
 

Sources/HTTPMock/HTTPMock.swift

@@ -6,14 +6,19 @@ public final class HTTPMock {
     public var defaultDomain = "example.com"
 
     public var unmockedPolicy: UnmockedPolicy {
-        get { HTTPMockURLProtocol.unmockedPolicy }
-        set { HTTPMockURLProtocol.unmockedPolicy = newValue }
+        get { HTTPMockURLProtocol.getUnmockedPolicy(for: mockIdentifier) }
+        set { HTTPMockURLProtocol.setUnmockedPolicy(for: mockIdentifier, newValue) }
     }
 
-    private init() {
-        let configuration = URLSessionConfiguration.ephemeral
-        configuration.protocolClasses = [HTTPMockURLProtocol.self]
-        urlSession = URLSession(configuration: configuration)
+    let mockIdentifier: UUID
+
+    public convenience init() {
+        self.init(identifier: UUID())
+    }
+
+    required init(identifier mockIdentifier: UUID) {
+        self.mockIdentifier = mockIdentifier
+        urlSession = URLSession.identifiedSession(with: mockIdentifier)
     }
 
     /// Queue responses for a given path (e.g. "/some-path") for host in `defaultDomain`. Each request will pop the next response.
@@ -28,7 +33,8 @@ public final class HTTPMock {
             forHost: defaultDomain,
             path: normalized(path),
             queryItems: queryItems,
-            queryMatching: queryMatching
+            queryMatching: queryMatching,
+            forMockIdentifier: mockIdentifier
         )
     }
 
@@ -45,7 +51,8 @@ public final class HTTPMock {
             forHost: host,
             path: normalized(path),
             queryItems: queryItems,
-            queryMatching: queryMatching
+            queryMatching: queryMatching,
+            forMockIdentifier: mockIdentifier
         )
     }
 
@@ -56,12 +63,12 @@ public final class HTTPMock {
 
     /// Clear all queues – basically a reset.
     public func clearQueues() {
-        HTTPMockURLProtocol.clearQueues()
+        HTTPMockURLProtocol.clearQueues(mockIdentifier: mockIdentifier)
     }
 
     /// Clear the response queue for a single host.
     public func clearQueue(forHost host: String) {
-        HTTPMockURLProtocol.clearQueue(forHost: host)
+        HTTPMockURLProtocol.clearQueue(forHost: host, mockIdentifier: mockIdentifier)
     }
 
     /// Makes sure all paths are prefixed with `/`. We need this for consistency when looking up responses from the queue.