Add CommonKit and Activity

Signed-off-by: Andy Uhnak <andyuhnak@gmail.com>

CommonKit/Source/Activity/Tests/ActivityCenterTests.swift

@@ -0,0 +1,55 @@
+// 
+// Copyright 2021 New Vector Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+import Foundation
+import XCTest
+
+class ActivityCenterTests: XCTestCase {
+    var activities: [Activity]!
+    var center: ActivityCenter!
+    
+    override func setUp() {
+        activities = []
+        center = ActivityCenter()
+    }
+    
+    func makeRequest() -> ActivityRequest {
+        return ActivityRequest(
+            presenter: ActivityPresenterSpy(),
+            dismissal: .manual
+        )
+    }
+    
+    func testStartsActivityWhenAdded() {
+        let activity = center.add(makeRequest())
+        XCTAssertEqual(activity.state, .executing)
+    }
+    
+    func testSecondActivityIsPending() {
+        center.add(makeRequest()).store(in: &activities)
+        let activity = center.add(makeRequest())
+        XCTAssertEqual(activity.state, .pending)
+    }
+    
+    func testSecondActivityIsExecutingWhenFirstCompleted() {
+        let first = center.add(makeRequest())
+        let second = center.add(makeRequest())
+        
+        first.cancel()
+        
+        XCTAssertEqual(second.state, .executing)
+    }
+}