Testing Extensions for Combine

Author: luizmb

Sources/TestingExtensions/CombineTesting.swift

@@ -0,0 +1,149 @@
+//
+//  CombineTesting.swift
+//  TestingExtensions
+//
+//  Created by Luiz Rodrigo Martins Barbosa on 23.03.21.
+//  Copyright © 2021 Lautsprecher Teufel GmbH. All rights reserved.
+//
+
+import Combine
+import XCTest
+
+extension XCTestCase {
+    @available(macOS 10.15, iOS 13.0, tvOS 13.0, watchOS 6.0, *)
+    public func assert<P: Publisher>(
+        publisher: P,
+        eventuallyReceives values: P.Output...,
+        andCompletes: Bool = false,
+        timeout: TimeInterval
+    ) -> () -> Void where P.Output: Equatable {
+        var collectedValues: [P.Output] = []
+        let valuesExpectation = expectation(description: "Expected values")
+        let completionExpectation = expectation(description: "Expected completion")
+        valuesExpectation.expectedFulfillmentCount = values.count
+        if !andCompletes { completionExpectation.fulfill() }
+        let cancellable = publisher.sink(
+            receiveCompletion: { result in
+                switch result {
+                case .finished:
+                    if andCompletes { completionExpectation.fulfill() }
+                case let .failure(error):
+                    XCTFail("Received failure: \(error)")
+                }
+            },
+            receiveValue: { value in
+                collectedValues.append(value)
+                valuesExpectation.fulfill()
+            }
+        )
+
+        return { [weak self] in
+            guard let self = self else {
+                XCTFail("Test ended before waiting for expectations")
+                return
+            }
+            self.wait(for: [valuesExpectation, completionExpectation], timeout: timeout)
+            XCTAssertEqual(collectedValues, values, "Values don't match:\nreceived:\n\(collectedValues)\n\nexpected:\n\(values)")
+            _ = cancellable
+        }
+    }
+
+    @available(macOS 10.15, iOS 13.0, tvOS 13.0, watchOS 6.0, *)
+    public func assert<P: Publisher>(
+        publisher: P,
+        eventuallyReceives values: P.Output...,
+        andCompletesWith: ValidateCompletion<P.Failure>,
+        timeout: TimeInterval
+    ) -> () -> Void where P.Output: Equatable {
+        var collectedValues: [P.Output] = []
+        let valuesExpectation = expectation(description: "Expected values")
+        let completionExpectation = expectation(description: "Expected completion")
+        valuesExpectation.expectedFulfillmentCount = values.count
+        let cancellable = publisher.sink(
+            receiveCompletion: { result in
+                XCTAssertTrue(andCompletesWith.isExpected(result), "Unexpected completion: \(result)")
+                completionExpectation.fulfill()
+            },
+            receiveValue: { value in
+                collectedValues.append(value)
+                valuesExpectation.fulfill()
+            }
+        )
+
+        return { [weak self] in
+            guard let self = self else {
+                XCTFail("Test ended before waiting for expectations")
+                return
+            }
+            self.wait(for: [valuesExpectation, completionExpectation], timeout: timeout)
+            XCTAssertEqual(collectedValues, values, "Values don't match:\nreceived:\n\(collectedValues)\n\nexpected:\n\(values)")
+            _ = cancellable
+        }
+    }
+
+    @available(macOS 10.15, iOS 13.0, tvOS 13.0, watchOS 6.0, *)
+    public func assert<P: Publisher>(
+        publisher: P,
+        completesWithoutValues: ValidateCompletion<P.Failure>,
+        timeout: TimeInterval
+    ) -> () -> Void {
+        let completionExpectation = expectation(description: "Expected completion")
+        let cancellable = publisher.sink(
+            receiveCompletion: { result in
+                XCTAssertTrue(completesWithoutValues.isExpected(result), "Unexpected completion: \(result)")
+                completionExpectation.fulfill()
+            },
+            receiveValue: { value in
+                XCTFail("Unexpected value received: \(value)")
+            }
+        )
+
+        return { [weak self] in
+            guard let self = self else {
+                XCTFail("Test ended before waiting for expectations")
+                return
+            }
+            self.wait(for: [completionExpectation], timeout: timeout)
+            _ = cancellable
+        }
+    }
+}
+
+@available(macOS 10.15, iOS 13.0, tvOS 13.0, watchOS 6.0, *)
+public struct ValidateCompletion<Failure: Error> {
+    let isExpected: (Subscribers.Completion<Failure>) -> Bool
+    public init(validate: @escaping (Subscribers.Completion<Failure>) -> Bool) {
+        self.isExpected = validate
+    }
+
+    public static var isSuccess: ValidateCompletion {
+        ValidateCompletion { result in
+            guard case .finished = result else { return false }
+            return true
+        }
+    }
+
+    public static var isFailure: ValidateCompletion {
+        ValidateCompletion { result in
+            guard case .failure = result else { return false }
+            return true
+        }
+    }
+
+    public static func failedWithError(_ errorPredicate: @escaping (Failure) -> Bool) -> ValidateCompletion {
+        ValidateCompletion { result in
+            guard case let .failure(error) = result else { return false }
+            return errorPredicate(error)
+        }
+    }
+}
+
+@available(macOS 10.15, iOS 13.0, tvOS 13.0, watchOS 6.0, *)
+extension ValidateCompletion where Failure: Equatable {
+    public static func failedWithError(_ expectedError: Failure) -> ValidateCompletion {
+        ValidateCompletion { result in
+            guard case let .failure(error) = result else { return false }
+            return error == expectedError
+        }
+    }
+}